Quantum Optics Resnick seminar

Imagine dragging a plate across the surface of a tranquil water pool. Quite excitingly, you would form a pair of swirling vortex and antivortex, propagating steadily across the surface. In optics, vortices manifest as phase twists of the electromagnetic field. While traditionally optical vortices arise from interactions between light and matter, I will present a new extreme regime of optical nonlinearity where quantum vortices – phase dislocations in the few-photon wavefunction – form due to effective, strong interactions between the photons themselves. These interactions are realized in a ‘quantum nonlinear optical medium’ based on ultracold Rydberg atoms. Analogous to the water pushed by the plate, the excess phase accumulating due to the photon-photon interaction gives rise to pairs of quantum vortices, vortex lines, and rings, within the photonic wavefunction. The ‘conditional’ phase flip localized between these vortices can be used for deterministic quantum logic operations.

The poor transport properties of organic semiconductors are often considered the Achilles' heel of these materials, placing severe limitations on the performances of organic-electronics devices. However, by embedding them in resonant photonic structures, their wavefunctions can be hybridized with light to create composite quantum excitations, which are partly photonic and partly excitonic.

In this talk I will show how this entanglement between light and matter can provide a novel pathway for enhancing the transport properties of materials, boosting the typical transport range from several nanometers to tens of microns. Furthermore, I will present our ultrafast time-resolved imaging measurements, where we revealed that the hybrid light-matter excitations exhibit a mobility transition between different types of transport mechanisms, governed by their composition. These results provide crucial insight into the mesoscopic quantities governing cavity-enhanced transport and pave the way towards novel organic electro-optic devices harnessing the coherent interaction between light and matter.

References

G. G. Rozenman, K. Akulov, A. Golombek, T. Schwartz, Long-range transport of organic exciton-polaritons revealed by ultrafast microscopy, ACS Photonics 5, 105 (2018).

M. Balasubrahmaniyam, A. Simkovich, A. Golombek, G. Sandik, G. Ankonina, T. Schwartz, From enhanced diffusion to ultrafast ballistic motion of hybrid light–matter excitations. Nature Materials 22, 338 (2023).

It is almost exactly 100 years since De-Broglie made public his outrageous hypothesis regarding Wave-Particle Duality (WPD), where the latter plays a key role in interferometry. In parallel, the Stern-Gerlach (SG) effect, found a century ago, has become a paradigm of quantum mechanics. I will describe the realization of a half- [1-3] and full- [4-5] loop SG interferometer for single atoms [6], including some recent results on the phase of freely falling objects, and show how WPD, or complementarity, manifests itself. I will then use the acquired understanding to show how this setup may be used to realize an interferometer for macroscopic objects doped with a single spin [5], namely, to show that even rocks may reveal themselves as waves. I emphasize decoherence channels which are unique to macroscopic objects such as those relating to phonons [7,8] and rotation [9]. These must be addressed in such a challenging experiment. The realization of such an experiment could open the door to a new era of fundamental probes, including the realization of previously inaccessible tests of the foundations of quantum theory and the interface of quantum mechanics and gravity, including the probing of exotic theories such as the Diosi-Penrose gravitationally induced collapse. Time permitting, and as an anecdote noting also De-Broglie's less popular assertion, namely, that the standard description of QM is lacking, I will also present our recent work on Bohmian mechanics, which is an extension of De-Broglie's ideas concerning the pilot wave [10].

PS I will not talk about quantum technology in this talk, but I invite those interested to talk to me about it, for example, our NV sensor or Yb optical atomic clock projects. Here are two recent quantum technology references [11,12]. More work from our group, such as an Yb optical clock or searches for dark matter, can be found on our website: https://tzin.bgu.ac.il/atomchip/  

[1] Y. Margalit et al., A self-interfering clock as a "which path" witness, Science 349, 1205 (2015); [2] Zhifan Zhou et al., Quantum complementarity of clocks in the context of general relativity, Classical and quantum gravity 35, 185003 (2018); [3] Zhifan Zhou et al., An experimental test of the geodesic rule proposition for the non-cyclic geometric phase, Science advances 6, eaay8345 (2020); [4] O. Amit et al., T³ Stern-Gerlach matter-wave interferometer, Phys. Rev. Lett. 123, 083601 (2019); [5] Y. Margalit et al., Realization of a complete Stern-Gerlach interferometer: Towards a test of quantum gravity, Science advances 7, eabg2879 (2021); [6] M. Keil et al., Stern-Gerlach interferometry with the atom chip, Book in honor of Otto Stern, Springer (2021); [7] C. Henkel and R. Folman, Internal decoherence in nano-object interferometry due to phonons, AVS Quantum Sci. 4, 025602 (2022) – invited paper for a special issue in honor of Roger Penrose; [8] C. Henkel and R. Folman, Universal limit on quantum spatial superpositions with massive objects due to phonons, PRA 110, 042221 (2024) - Editor's suggestion; [9] Y. Japha and R. Folman, Role of rotations in Stern-Gerlach interferometry with massive objects, Phys. Rev. Lett. 130, 113602 (2023) [10] G. Amit et al., Countering a fundamental law of attraction with quantum wave-packet engineering, Phys. Rev. Res. 5, 013150 (2023); [11] Z. Zhou, Geometric phase amplification in a clock interferometer for enhanced metrology, https://arxiv.org/abs/2405.10226 (2024); [12] Y. Halevy et al., Chip-Scale Point-Source Sagnac Interferometer by Phase-Space Squeezing, https://arxiv.org/abs/2405.16972 (2024).

Temporal optics revolutionized the field of ultrafast measurements. With advanced temporal devices, we studied for the first time the dynamics of rouge waves, soliton interactions, and the beginning of lasing. We are aiming to adopt temporal optics into the quantum optics world. In the talk, I will describe temporal optics, the different stages in developing temporal quantum optics devices, what we are hoping to find with it, and the open questions that need to be answered

Theoretical treatment of resonance interaction, which provides a key ingredient in modern research with ultracold atomic gases, is relatively complex because many collisional channels are usually involved. I will describe a lazy experimentalist's approach to deal with these complications and show that the well-established coupled-channel calculation phenomenology of lithium can be qualitatively reproduced, illuminating its particularities. This approach can be readily extended to other atomic species.

 In the last couple of decades, there have been dramatic advances in the generation, manipulation, and detection capabilities of THz waves (0.1-10 THz). These advances forecast a variety of emerging desirable applications. However, despite the immense recent progress in THz technologies, there is still a substantial lack of simple methods to generate fully controlled THz waveforms. In my talk, I will present the recent advancements in the ability of nano-engineered plasmonic metasurfaces to generate broadband and highly controlled THz waves. I will elucidate the underlying physical mechanisms that make the THz emission from the metasurfaces comparable in strength to that emitted from orders of magnitude thicker nonlinear crystals, excited at the same conditions. I will also show that simple electromagnetic considerations allow to further enhance the THz radiation from the metasurfaces by more than an order of magnitude. In addition, I will demonstrate how to utilize the well-known Pancharatnam-Berry phase to obtain unprecedented spatio-temporal control over the amplitude, phase, and polarization of the emitted THz waves, opening the door for holographic THz emitters. 

Anisotropic particles are prevalent in a wide range of systems, ranging from ice and snow particles, to liquid crystal droplets, biological structures, magnetized plasmas, and ferromagnetic and anisotropic-phonon bulk particles. In particular, nanostructures synthesized from anisotropic phonon-supporting bulk hold promise for a new generation of high-Q tunable and directional resonators which cover unexplored midinfrared regions. However, only the dipole mode of anisotropic spherical and ellipsoidal particles has been analytically derived and experiments on the modes and resonances of such particles remain to be performed. Here, we develop an analytic theory of the complete response of subwavelength anisotropic particles, which exhibit axial-permittivity resonance sum rules. We then confirm our theoretical predictions by synthesizing biaxial particles and performing near-field measurements, with excellent agreement. Our research may find applications in devices for vibrational spectroscopy, thermal imaging, and detection of dark matter. Our theoretical analysis applies to other fields of physics such as quasi-magnetostatics and heat conduction.

Electrically controlled photonic circuits hold promise for information technologies with greatly improved energy efficiency and quantum information processing capabilities. However, weak non-linearity and lack of electrical response of typical photonic materials have been two critical challenges. Therefore hybrid electronic-photonic systems, such as semiconductor exciton-polaritons, super-position states of confined photons and matter excitations, have been intensely investigated for their potential to allow higher nonlinearity and electrical control, but with limited success so far, as such non-polar particles do not interact sufficently with either electric fields or with other particles. 
We demonstrate light circuits based on photons confined in planar waveguide geometries that are quantum mechanically hybridized with 2D-excitons that can be electrically polarized using electrical gates. The ability to hybridize dipolar excitons with confined photons allow formation of polaritons which carry effective dipole moments, leading to "interacting dipolar photons". This new concept leads to novel ways to control polaritons motion electrically, as well as tuning the position and strengths of their mutual interaction, that can reach surprisingly huge values.
Here, a new class of planar waveguide devices are shown, that elucidate the exciting physics that can be explored and the pormising quantum-photonic applications that can be developed with such on-chip dipolariton circuits: we demonstrate that remarkably, “dipolar light” can very effectively undergo coherent scattering from local electrical potentials, in a manner consistent with quantum scattering theory of ultra-light dipolar particles.
Then, we demostrate an ultrafast electrical mirror for photons with a GHz switching time, and then an electrically controlled photon transistor based on enhanced dipolar interactions between slow polaritons. The polariton transistor displays blockade and anti-blockade by compressing a dilute dipolar-polariton pulse exhibiting very strong dipolar interactions.
Finally, we demonstrate photon correlation measurements from a transistor with resonantly injected dipolaritons,displaying both anti-bunching and bunching, reconfigured and tuned simply by changing the gate voltage, showing that such electrically controlled planar geometry of waveguided

Our research deals with the application of laser light to accelerate electron beams in free space, using nanophotonic structures [1-4]. This technology is unique among other particle acceleration technologies in that it is inherently miniaturized, thereby having the potential to be directly inserted into the human body on endoscopes for localized tumor irradiation, or compactly designed to fit on a small optical table or for space applications. Moreover, it offers high repetition rate (100's of kHz to MHz and potentially GHz) electron pulses, dependent only on the laser technology used to drive it – itself a femtosecond, nowadays commercially-available standard laser. Conversely, traditional high-energy electron accelerators generally involve infrastructure spanning several kilometers and hundreds of employees, such as the Stanford linear accelerator (SLAC), or state-of-the-art peta-Watt lasers which are typically pulsed at far less than 1 pulse per second.
In this talk, I will briefly mention our work on the photo-induced near-field electron microscopy (PINEM) effect [5], in which the quantization of the electron's spectrum due to repeated interaction with photons can be measured. I will show how this quantization relates to energy modulation which is at the basis of electron acceleration. I will then mainly focus on our recent experimental achievement [3] – a proof-of-concept experiment showing that the on-chip electron accelerator works. Although feasible "on-paper", it was not straightforward to realize this in the lab. This feat required the conjoined efforts of different fields and tools: accelerator physics, nanophotonics, nanofabrication, electromagnetics, among others. We will review all the ingredients needed to construct the accelerator on a chip – and discuss the next steps.
[1] R. J. England et al., Dielectric Laser Accelerators, Reviews of Modern Physics 86, 1337 (2014).
[2] R. Shiloh, T. Chlouba, P. Yousefi, and P. Hommelhoff, Particle Acceleration Using Top-Illuminated Nanophotonic Dielectric Structures, Optics Express 29, 14403 (2021).
[3] T. Chlouba, R. Shiloh, S. Kraus, L. Brückner, J. Litzel, and P. Hommelhoff, Coherent Nanophotonic Electron Accelerator, Nature 622, 476 (2023).
[4] R. Shiloh, J. Illmer, T. Chlouba, P. Yousefi, N. Schönenberger, U. Niedermayer, A. Mittelbach, and P. Hommelhoff, Electron Phase Space Control in Photonic Chip-Based Particle Acceleration, Nature 597, 498 (2021).
[5] R. Shiloh, T. Chlouba, and P. Hommelhoff “Quantum-coherent light-electron interaction in an SEM,” Phys. Rev. Lett. 128 235301 (2022), selected as Editor’s Suggestion and Featured in Physics 15, 80.

Photonic integrated circuits in the standard silicon-on-insulator layers stack represent a key technology for large-scale data communication. Silicon photonics is also a promising platform for signal processing, sensing, and quantum science and technology. One function that remains difficult to realize in silicon photonic circuits is the true time delay of optical waveforms: the speed of light is simply too fast. Optical delay lines require excessive path lengths which are difficult to accommodate on-chip, and they are also associated with impractical propagation losses. An effective solution is known for decades in analog radio-frequency electronic circuits: the conversion of incoming signals to slow-moving surface acoustic waves. However, surface acoustic wave devices require piezo-electric interfaces.

Over the last five years, our group has introduced and implemented a new concept of surface acoustic wave – photonic devices. Rather than rely on electronic interfaces and piezo-electric materials, incoming waveforms are directly converted from the modulation of optical carriers to the form of surface acoustic waves in standard silicon. Conversion relies on the absorption of the modulated carrier in metallic structures and their subsequent thermo-elastic expansion. The signals of interest are re-converted to the optical domain through photo-elastic modulation of a second optical carrier in a resonator waveguide circuit. The devices are realized in the standard silicon-on-insulator workhorse layers stack. Applications examples include true time delays up to 170 ns on-chip, narrowband microwave-photonic filters, elastic analysis of thin layers deposition, and microwave-frequency oscillators. Lastly, the enhancement of thermo-elastic actuation through plasmon resonant absorption will be presented as well.

I will describe two recent results in research of mode-locked lasers:

1. Dissipative solitons are fundamental wave‑pulses that preserve their form in the presence of periodic loss and gain. The canonical realization of dissipative solitons is Kerr‑lens mode locking in lasers, which delicately balance nonlinear and linear propagation in both time and space to generate ultrashort optical pulses. This linear‑nonlinear balance dictates a unique pulse energy, which cannot be increased (say by elevated pumping), indicating that excess energy is expected to be radiated in the form of dispersive or diffractive waves. I will present an experiment and simulation to demonstrate that Kerr‑lens mode‑locked lasers can overcome this expectation. Specifically, by breaking the spatial symmetry between the forward and backward halves of the round‑trip in a linear cavity, the laser can modify the soliton in space to incorporate the excess energy.
   
    Scientific Reports 12, 14874 (2022), Idan Parshani, Leon Bello, Mallachi-Elia Meller and Avi Pe’er, “Passive symmetry breaking of the space–time propagation in cavity dissipative solitons”,

2. Mode locking in semiconductor lasers is a long-saught goal in laser research. I will present our recent achievement of a mode-locked semiconductor laser oscillator with record-high performance of 5-8ps pulses and record peak power of 112W. To achieve this high power performance we employ a high-current broad-area, spatially multi-mode diode amplifier, placed in an external cavity that enforces oscillation in a single spatial mode. Mode locking is achieved by dividing the large diode chip (edge emitter) into two sections with independent electrical control: one large section for gain and another small section for a saturable absorber. Precise tuning of the reverse voltage on the absorber section allows to tune the saturation level and recovery time of the absorber, providing a convenient knob to optimize the mode-locking performance for various cavity conditions.
   
   Optics Express 31, 41979 (2023), Mallachi-Elia Meller, Leon Bello, Idan Parshani, David Goldovsky, Yosef London and Avi Pe’er, “High-energy picosecond pulses with a single spatial mode from a passively mode-locked, broad-area semiconductor laser”,

2D materials are elastic materials that can sustain high strain. While the response of these materials to spatially uniform strain is well studied, the effects of spatially non-uniform strain are understood much less. In this talk I will show the response of transition metal dichalcogenides monolayers under non-uniform strain. It was predicted that non-uniform strain will allow transport or “funneling” of neutral charge excitons which can be useful as an efficient solar cell^[1].  I show that while transport or “funneling” of excitons is relatively inefficient, a different process, a strain-related conversion of excitons to trions is dominant and is universal for any configuration of non-uniform strain^[2-3]. Lastly, I will discuss different experimental directions that will allow high “funneling” efficiency by straining heterostructures^[4,5].

1. J. Feng, X. Qian, C.-W. Huang, and J. Li, Nature Photonics 6, (2012), 866–872.
2. M. G. Harats, J. N. Kirchhof, M. Qiao, K. Greben, and K. I. Bolotin, Nature Photonics, 14 (5), (2020), 324-329
3. S. Kovalchuk, M. G. Harats, G. López-Polín, J. N. Kirchhof, K. Höflich, K. I. Bolotin, 2D Materials 7 (3), (2020), 035024
4. M. G. Harats, K. I. Bolotin, 2D Materials 8 (1), (2020), 015010
5. S. Kovalchuk, J. N. Kirchhof, K.I. Bolotin, M. G. Harats, Israel Journal of Chemistry 62 (3-4), (2022), e20210011

For the past two decades harmonically trapped ultracold atomic gases have been used with great success to study fundamental many-body physics in flexible experimental settings. However, the resulting gas density inhomogeneity in those traps makes it challenging to study paradigmatic uniform-system physics (such as critical behavior near phase transitions) or complex quantum dynamics.

The realization of homogeneous quantum gases trapped in optical boxes has marked a milestone in the quantum simulation program with ultracold atoms [1]. These textbook systems have proved to be a powerful playground by simplifying the interpretation of experimental measurements, by making more direct connections to theories of the many-body problem that generally rely on the translational symmetry of the system, and by altogether enabling previously inaccessible experiments. 


I will present a set of studies with ultracold fermions trapped in a box of light [2-4]. This platform is particularly suitable to study problems of Fermi-system stability, of which I will discuss two cases: the spin-1/2 Fermi gas with repulsive contact interactions [2], and the three-component Fermi gas with spin-population imbalance [3]. Both studies lead to surprising results, highlighting how spatial homogeneity not only simplifies the connection between experiments and theory, but can also unveil unexpected outcomes. Finally, I will discuss two ongoing efforts to tackle far-from-equilibrium dynamics of uniform fermions.


[1] N. Navon, R.P. Smith, Z. Hadzibabic, Nature Phys. 17, 1334 (2021)

[2] Y. Ji et al., Phys. Lev. Lett 129, 203402 (2022)

[3] G.L. Schumacher et al., arXiv:2301.02237

[4] Y. Ji et al., arXiv:2305.16320

Experimental study of ultracold ⁴⁰Ca plasma

This work describes the approach that makes possible creation of the steady-state ultracold plasma having various densities and temperatures by means of continuous two-step optical excitation of ⁴⁰Ca atoms in the MOT. A strongly coupled ultracold plasma can be used as an excellent test platform for studying many-body interactions associated with various plasma phenomena. The parameters of the plasma are studied using laser-induced fluorescence of calcium ions. The strongly coupled plasma with the peak ion density of 2.7X10⁶  cm^-3 and the minimum electron temperature near 2K has been prepared. The experimental setup for laser cooling of ⁴⁰Ca atoms enables the capture of approximately 3X10⁷  atoms in the trap. Spectra of Rydberg transitions in n¹S₀ states were recorded for n ranging from 40 to 120. The energies of these transitions allowed for the determination of the most precise value of the ionization potential, which is 49305.91966(4) cm^-1 compared to known data. A sensitive diagnostic method for sparse ultracold plasma, based on the autoionization effect of Rydberg states of ⁴⁰Ca atoms, has been developed. This method enables the detection of plasma with ion concentrations of up to 10³  cm^-3, roughly equivalent to an electric field intensity of  10^-2  V/m.

Quantum many-body systems are at the heart of various research fields, including nuclear, atomic, and condensed-matter physics. Fascinated by the beauty and elegance of universal features common to very different and complex many-body systems, I focus on studying universality and on utilizing it for developing predictive tools for the many-body system. Specifically, I will present a theory for describing short-range physics in such systems. To demonstrate its validity, I will consider nuclear systems, and show how it provides a comprehensive picture of short-range correlations and captures quantitatively the impact of short-range correlated pairs on different quantities. I will then focus on recent efforts to construct a systematic framework for the description of short-range physics, extending the relevance and applicability of the theory and opening the path for description of different properties of quantum many-body systems. I will discuss the connection to major experimental efforts in nuclear physics and beyond, studies of physics beyond the Standard Model, and relevance to different subfields of physics. If time permits, I will also share my work on quantum computing and plans for the future, with the goal of providing an accurate description of dynamics in quantum many-body systems.

Quantum photonics often relies on nonlinear optics for the generation of photons, followed by reconfigurable linear optical networks for coherent control. In this talk, I will review our study of multimode nonlinear optics in fibers [1,2], which also enabled our realization of an all-fiber entangled photon pairs source [3]. These photons are spatially entangled in the eigenmodes of the multimode fiber, allowing for high-dimensional quantum communications. I will then present a couple of methods to coherently control such states. The first is achieved by multiplane light conversion based on a spatial light modulator [4], while the second is by employing a “Fiber piano” [5]; a piezo-actuator array that deforms the multimode fiber. Finally, I will introduce a novel Quantum Key Distribution protocol that utilizes high-dimensional encoding to boost the secure key rate and its experimental implementation [6].

[1] Kfir Sulimany, et al. Physical Review Letters 121.13 (2018): 133902. 

[2] Kfir Sulimany, et al. Optica 9.11 (2022): 1260-1267. 

[3] Kfir Sulimany, and Yaron Bromberg. npj Quantum Information 8.1 (2022): 1-5. 

[4] Ohad Lib, Kfir Sulimany, and Yaron Bromberg. Physical Review Applied 18.1 (2022): 014063. 

[5] Finkelstein, Zohar, Kfir Sulimany, et al. APL Photonics 8, no. 3 (2023).

[6] Kfir Sulimany, et al. arXiv preprint arXiv:2105.04733 (2021). Under review.

In the last decade, strong-field laser driving in solids has been employed for developing novel ultrafast spectroscopies. It has allowed (among others) probing band structures, Berry curvatures, phase transitions, and correlations. Here, intense laser pulses irradiate a sample, triggering non-perturbative responses such as high harmonic generation (HHG), photocurrent generation, etc.; which are analyzed to obtain information about the sample and (potentially attosecond) dynamics within it. These spectroscopies require an intimate comparison between theory and experiment, and a deep understanding of the underlying physical mechanisms generating the response. However, theories often involve many untested approximations, and the fundamental mechanisms behind HHG are still under debate. This issue is further complicated by the potential simultaneous presence of Floquet light-dressed phases of matter that could affect the dynamics. I will present our recent efforts exploring the fundamental nature of intense light-matter interactions in solids from an ab-initio perspective. First, I’ll show that Floquet physics indeed arises in the strong-field regime[1], but its contribution is quite complex and depends on the particular process being studied[2,3]. I’ll argue that by performing time- and angle-resolved photoemission spectroscopy (Tr-ARPES) one can probe the interplay of Floquet phases and highly nonlinear optics. Next I’ll present our recent work on HHG spectroscopy of topological insulators[4], which suggests that topology plays a rather minor role in highly nonlinear optics, contrary to the common conception in the field. Lastly, I’ll show that strong-field laser irradiation allows inducing non-perturbative attosecond magnetization dynamics[5], which are the fastest laser-induced magnetic responses predicted to date.

[1] Neufeld et al., Nano. Lett. 23, 7568 (2023). https://doi.org/10.1021/acs.nanolett.3c02139.

[2] Neufeld et al., PRResearch 4, 033101 (2022). https://doi.org/10.1103/PhysRevResearch.4.033101.

[3] Galler, Rubio, and Neufeld, JPCL 14, 11298 (2023). https://pubs.acs.org/doi/10.1021/acs.jpclett.3c02936.

[4] Neufeld et al., PRX 13, 031011 (2023). https://doi.org/10.1103/PhysRevX.13.031011.

[5] Neufeld et al., npj Comp. Mat. 9, 39 (2023). https://doi.org/10.1038/s41524-023-00997-7.

Photonic quantum computing presents a viable and fascinating path to fault-tolerant quantum computing. I will present our endeavor and results toward this goal, using the paradigm of measurement-based quantum computing. Working the quantum optics of the multitude of resonant cavity (qu)modes of an optical parametric oscillator, we have generated cluster entangled states with 60 characterized qumodes (out of 10,000 likely present). On the theory side, we have shown that scalable hypercubic cluster states can be generated with relatively scarce experimental resources, such as one OPO and one electro-optic modulator. I will also show that judicious use of photon-number-resolving detection should enable us to leverage the massive scalability of these Gaussian continuous-variable cluster states by de-Gaussifying them into identical cluster states of Gottesman-Kitaev-Preskill qubits, paving the way to foliated topological error codes.

Bio:

Olivier Pfister received the B.S. in Physics from Université de Nice, France, in 1987, and the M.S. and the Ph.D. in Physics from Université Paris-Nord, France, in 1989 and 1993. In 1994, he was a lecturer at INM, Conservatoire National des Arts et Métiers, in Paris. He was then a research associate with John L. Hall at JILA, University of Colorado (1994-97) and with Daniel J. Gauthier at Duke University (1997-99). In 1999, he joined the faculty of the University of Virginia, where he is a professor of physics and of electrical and computer engineering. Olivier Pfister is a fellow of the American Physical Society and a member of Optica, IEEE, and SPIE. His general research area is atomic, molecular, and optical physics, with past interests in quantum measurements at the ultimate precision, ultrahigh resolution laser spectroscopy, symmetry effects in small molecules, nonlinear optics for optical frequency chains, and two-photon lasers. His current research interest is quantum computing with light. He is also a co- founder and CTO of quantum computing startup QC82, Inc.

Silicon detectors are widely used as high-performance sensors for photons from 1 eV energy up to hundreds of keV and as particle detectors for tracking, imaging and spectroscopy. In the visible domain CCDs, CMOS imagers and SiPMs are spread over a wide range of scientific applications. In the UV and X-ray range from 20 eV up to 20 keV the direct detection of the photons is usually done on back-illuminated fully depleted, thus fully sensitive silicon detectors: Silicon Drift Detectors, pnCCDs and CMOS based Active Pixel Sensors or hybrid CMOS detectors. For higher X-ray energies, up to 1 MeV the signal conversion into visible photons is performed in scintillators coupled to light sensitive detectors.  High spatial resolution direct electron detection for TEMs and SEMs are equally achieved with dedicated silicon sensors based on pnCCDs and DePFET active pixel sensors. The description of the physical limits of the measurement precision will be derived as well as the semiconductor device concepts to get as close as possible to these limits. New developments and applications in basic and applied science will be highlighted as well as scientific instrumentation for industry.

Molecular plasmonics has been a hot topic for the past several years. At the heart of the primary interest in plasmonics is the strong electromagnetic field localization at resonant frequencies corresponding to surface plasmon-polariton modes. Thanks to riveting advancements in nanofabrication technologies, we have achieved nearly 1 nm spatial resolution (and in some cases even below that!) and are able to fabricate a wide variety of nanosystems ranging from
nanoparticles of various shapes to metasurfaces comprised of periodic arrays of nanoparticles and/or nanoholes of any imaginable geometry. Such systems have recently emerged as new platforms for strong light-matter interactions. Combined with molecular ensembles, these constructs exhibit a remarkable set of optical phenomena ranging from the exciton-plasmon strong coupling to the second harmonic generation altered by molecular resonances. In this talk I will discuss both linear and nonlinear optical properties of plasmonic materials coupled to quantum emitters of various complexity. I will also introduce a newly developed computational approach that can be used to efficiently simulate a large number of complex molecules driven by electromagnetic radiation crafted at plasmonic interfaces.

Representative publications:
1. “Efficient parallel strategy for molecular plasmonics – a new numerical tool for Maxwell-Schrödinger equations in three dimensions”, M. Sukharev, Journal of Computational Physics 477, 111920 (2023).
2. “Dissociation slowdown by collective optical response under strong coupling conditions”, M. Sukharev, J. Subotnik, A. Nitzan, (Editor’s Choice) Journal of Chemical Physics 158, 084104 (2023).
3. “Fano plasmonics goes nonlinear”, M. Sukharev, E. Drobnyh, R. Pachter, Journal of Chemical Physics 157, 134105 (2022).
4. “Second harmonic generation by strongly coupled exciton-plasmons: the role of polaritonic states in nonlinear dynamics”, M. Sukharev, A. Salomon, J. Zyss, Journal of Chemical Physics 154, 244701 (2021).
5. “Second harmonic generation from a single plasmonic nanorod strongly coupled to a WSe2 monolayer”, C. Li, X. Lu, A. Srivastava, S. D. Storm, R. Gelfand, M. Pelton, M. Sukharev, H. Harutyunyan, Nano Letters 21, 1599 (2020).
6. “Plasmon enhanced second harmonic generation by periodic arrays of triangular nanoholes coupled to molecular emitters”, E. Drobnyh and M. Sukharev, Journal of Chemical Physics 152, 094706 (2020).
7. “Energy transfer and interference by collective electromagnetic coupling”, M. Gómez-Castaño, A. R. Cubero, L. Buisson, J. L. Pau, A. Mihi, S. Ravaine, R. A. L. Vallée, A. Nitzan, M. Sukharev, Nano Letters 19, 5790 (2019).

From carefully crafted quantum algorithms to information-theoretic security in cryptography, a quantum computer can achieve impressive feats with no classical analogue. Can their correct realization be verified? When the power of the device greatly surpasses that of the user, computationally as well as cryptographically, what means of control remain available to the user?

Recent lines of work in quantum cryptography and complexity develop approaches to this question based on the notion of an interactive proof. Generally speaking an interactive proof models any interaction whereby a powerful device aims to convince a restricted user of the validity of an agree-upon statement -- such as that the machine generates perfect random numbers or executes a specific quantum algorithm.

Two models have emerged in which large-scale verification has been shown possible: either by placing reasonable computational assumptions on the quantum device, or by requiring that it consists of isolated components across which Bell tests can be performed.

In the talk I will discuss recent results on the verification power of interactive proof systems between a quantum device and a classical user, focusing on the certification of quantum randomness from a single device (arXiv:1804.00640) and the verification of arbitrarily complex computations using two devices (arXiv:2001.04383).

Current quantum computers are on the one hand too small and noisy for implementing quantum error correction codes, and on the other hand not reliable enough for running calculations without error correction codes. Quantum error mitigation (QEM) is an emerging new approach that aims to generate reliable outputs using the currently available quantum computers. QEM methods can substantially mitigate the noise by running additional measurements that extract information about the noise. Unfortunately, these methods are either non-scalable, or heuristic and valid only for a specific nonrealistic noise model. We present a QEM technique we call KIK which is derived from a rather general Master equation. This method can handle a broad range of time-dependent noise mechanisms even when their amplitude is considerably strong. In the first stage, we intend to apply our method for ground state calculations of molecules in quantum computers and for producing better calibration procedures for quantum gates. Finally, a spin off of our method can be used to efficiently measure the quantum fidelity of a circuit without knowing what is the ideal output state.

Physical systems can be tuned to an absorbing exceptional point (EP) at which both the eigenfrequencies and eigenmodes associated with perfect capture of an input wave coalesce. We find that a time-domain signature of absorbing EPs is an expansion of the class of waveforms which can be perfectly captured. We show that such systems have improved performance for storage or transduction of energy and that they can be used to convert between waveforms within this class. Finally, we demonstrate that these waveforms can be naturally generated at high frequencies. If time permits, we will explore the possibility of exciting high-order atomic and molecular multipoles in the far field with potential to achieve subatomic resolution, and vibrational modes of helical structures and their coupling to electromagnetic fields.

In this talk, I will present my journey moving from working with single photons to continuous variables. The signal-to-noise ratio (SNR) of range measurements can be improved by quantum detection and quantum light sources (quantum ranging). In the first part, I will present the theory of quantum ranging in the framework of Gaussian states. I will show that an optimal detection strategy, which minimizes the detection errors, can be applied for an arbitrary return state from the target. Then I will discuss the use of quantum light in the same scenario. Optimal detection is important in high-loss mediums, such as underwater, where low signal returns and maximizing its information is needed. In the second part, I will present experimental results of improved sensitivity of a temperature sensor and quantum simulations with single photons and will present my plans to extend the theory and experiments to Gaussian states. I will show simulations of a basic transition of quantum gravity theory and discuss scaling it up to complex transitions. Complex versions of these simulations have the potential to advance the research of basic science.

An important, yet sometimes understated, property of 2D materials is that they are embedded in a 3D environment, which makes them amenable to external manipulation in ways in which 3D materials are not. In this talk, I will demonstrate how this concept can be applied to confine hyperbolic phonon polaritons volumes 8 orders of magnitude smaller than the volume of a vacuum photon (λ₀³), while still maintaining an appreciable quality factor (Q~100). This breaks away from the nanophotonics paradigm that deep subwavelength  cavities always exhibit low quality factors (high absorption). These new cavities pave the way to exciting cavity quantum electrodynamics experiments, novel multimodal interaction effects and Floquet driving physics.

The ability to control and manipulate free electrons and light is interesting for its fundamental aspects, while its development for imaging applications has seen great progress, enabling imaging at increasing sensitivity and resolution. Recent developments in quantum information and quantum metrology have inspired a growing interest in developing techniques that manipulate free electrons and light to attain quantum limits in imaging applications. In the first part of the talk, I will focus on electron microscopy, where I will describe a technique to manipulate the transverse wavefront of free electrons using thin photodiodes illuminated with patterned continuous wave light. I will then discuss progress towards realizing a quantum-inspired technique to enhance the dose efficiency of electron microscopes that approaches the quantum limit for imaging of single molecules with atomic resolution. In the second part of the talk, I will present a classical technique to enhance the sensitivity and throughput of imaging a dynamic sample that approaches the quantum limit, surpassing sensitivity enhancement of all previous demonstrations of imaging that use squeezed light or entanglement 

The optical properties of materials are universally described within the electric dipole (ED) approximation—atomic-scale optical frequency light-matter interactions are assumed to arise solely from electric dipoles interacting with the electric field component of light. In fact, this inability of matter to interact with the magnetic-field component of light led to the advent of metamaterials and metasurfaces. In this talk, I describe my group’s recent discovery of atomic-scale optical magnetism in 2D Layered Hybrid Organic/Inorganic Pervoskites (2D HOIPs). First, I detail our use of momentum-resolved optical spectroscopy to demonstrate magnetic dipole (MD) light emission originating from self-trapped excitons [1,2]. I conclude by showing that 2D HOIPs are the only known materials to exhibit non-unity optical frequency magnetic permeabilities [3].

[1] DeCrescent, R.A., Venkatesan, N.R., Dahlman, C.J., Kennard, R.M., Zhang, X., Li, W., Du, X., Chabinyc, M.L., Zia, R. and Schuller, J.A., 2020. Bright magnetic dipole radiation from two-dimensional lead-halide perovskites. Science advances, 6(6), p.eaay4900.

[2] DeCrescent, R.A., Du, X., Kennard, R.M., Venkatesan, N.R., Dahlman, C.J., Chabinyc, M.L. and Schuller, J.A., 2020. Even-Parity Self-Trapped Excitons Lead to Magnetic Dipole Radiation in Two-Dimensional Lead Halide Perovskites. ACS nano, 14(7), pp.8958-8968.

[3] DeCrescent, R.A., Kennard, R.M., Chabinyc, M.L. and Schuller, J.A., 2021. Optical-Frequency Magnetic Polarizability in a Layered Semiconductor. Physical Review Letters, 127(17), p.173604.

Bio:

Jon A. Schuller graduated from UCSB with a B.S. degree in physics before completing a Ph.D. in Applied Physics at Stanford University. Jon joined the electrical and computer engineering department at UC Santa Barbara in 2012, and is currently a Full Professor. Jon’s research interests include reconfigurable photonics, semiconductor metasurfaces, and advanced spectroscopy of nanomaterials. He is the recipient of an AFOSR Young Investigator Award and NSF CAREER award.

Optically-active solid-state spin systems can offer remarkable single photon emission properties (brightness and indistinguishability), which makes them useful for developing photonic quantum simulators and building blocks of quantum networks (“the future internet”). In this talk, I will present the efforts of studying the fundamental physics of optically-active spin systems and integrating such systems in photonic platforms for quantum technologies. First, I will present the methods for controlling the quantum state of optically-active spin qubits and the experimental protocols for probing the physics of the qubits’ environment. Then, I will describe the process of coupling optically-active spin systems to photonic cavities, which provides spin-dependent optical switching capabilities for quantum networking. Finally, I will describe the applications of optically-active spins in photonic cavities for simulating quantum dynamics under complex Hamiltonians, as well as toward the demonstration of photonic quantum repeaters for the efficient distribution of information between quantum computers.

The field of quantum metrology seeks to develop quantum protocols to enhance the precision of measurements and it is one of the pillars of quantum science and technology. The general tools and bounds of quantum metrology assume perfect detection. However, the detection in most quantum experimental platforms is noisy and imperfect. We fill this gap and develop a theory that takes into account general measurements . We generalize the precision bounds to account for arbitrary detection channels. We find the general form of the precision bounds and of the optimal control for pure states. We then consider quantum states in a multi-partite system and study the impact of detection noise on quantum enhancement in sensitivity. Interestingly, the achievable sensitivity depends crucially on the allowed control operations. For local optimal control, the detection noise severely degrades the sensitivity and limits any quantum enhancement to a constant factor. On the other hand, with optimal global control the detection noise can be completely removed and the noiseless sensitivity bounds can be retrieved for a generic class of quantum states (including all pure states and symmetric states).

Based on https://www.nature.com/articles/s41467-022-33563-8, https://arxiv.org/abs/2210.11393

Quantum metrology allows increasing the sensitivity of the measurements of the physical parameters by exploiting quantum features of the probes and measurements. The advantages of quantum techniques were already demonstrated experimentally for the problems of phase estimation (that was used for gravitational wave detection) and quantum imaging. An important model example of a quantum imaging problem is the separation estimation of the two point-sources. It allows to better understand the connection between the state of the emitted light, properties of the measurement, and the resulting resolution. In addition, this problem itself has a number of practical applications in astronomical observation, fluorescent microscopy, etc.

Intense analysis of the separation estimation problem during past years showed, that the traditional approach of measuring emitted field intensity (called direct imaging) often leads to the vanishing of the information about the separation when the separation is small. This feature is known as the “Raleigh curse”. At the same time, measurements in specific spatial modes, e.g. Hermit-Gauss modes, do not lead to this kind of problem. Another important aspect of this problem is the state of the emitted light. The role of the sources’ coherence sparked hot debates during recent years, which made us to address this problem. In our research we analyze separation estimation between pair of mutually coherent sources, making no assumptions about quantum statistics of emitted light, absolute and mutual brightness of the sources. We show that anti-bunching of the sources' radiation leads to an increase of the sensitivity, but at the same time ignorance of sources brightness wipes out any possible profit from non-classical statistics of the sources.

Optically-active spins in the solid-state are useful resources for quantum technologies, including quantum computing, networking, and sensing. In particular, artificial atoms and molecules in direct bandgap semiconductors can be used to generate single photons with high efficiency and indistinguishability, as well as entangled photon states for the realization of quantum algorithms. Ideal spin systems for such applications must combine high quality optical and spin properties, and an efficient method for coherently controlling the spin. In this talk, I will describe the methods for coherently controlling optically-active spin qubits in quantum photonic platforms.

First, I will present an all-optical Raman-based realization of such coherent control for the high frequency noise spectroscopy of solid-state spins. The physical understanding of solid-state environments gained by such noise spectroscopy is essential for the development of spin qubits with long coherence times in noisy environments.

After discussing these fundamental studies, I will describe the ongoing research directions aimed at coupling solid-state spins to fabricated photonic structures for the implementation of multi-pulse control sequences for quantum information processing, as well as for the deterministic generation of spin-photon entanglement on-chip. In particular, I will present the potential of gratings fabricated in charge tunable devices for upgrading the photonic interface of optically-active spin systems.

Finally, I will introduce novel systems with promising spin and optical properties that remain highly unexplored, such as telecom wavelength emitters and self-assembled quantum dot molecules. Coherently controlling the spin of such systems embedded in photonic structures could enable the realization of novel pulse sequences for high resolution sensing, quantum information processing, and quantum networking.

Dielectric laser accelerators (DLA) are, fundamentally, the interaction of photons with free electrons, where energy and momentum conservation are satisfied by mediation of a nanostructure. In this scheme, the photonic nanostructure induces near-fields, which transfer energy from the photon to the electron via the inverse-Smith-Purcell effect [1,2]. Research in this direction is a wonderful opportunity to engage in multi-disciplinary science, because it directly involves accelerator physics, quantum physics, electron microscopy, ultrafast lasers, near-field optics, and nanofabrication.

There is great potential for DLA to provide ground-breaking applications, as it is the only technology promising to miniaturize particle accelerators down to the chip-scale. This is because dielectric materials allow using an order of magnitude larger electric fields, relative to metallic radiofrequency (RF) acceleration cavities. Further, modern ultrafast lasers are perfectly poised to induce these high fields, and have additional advantages over RF technology, including high repetition rates, femtosecond temporal period, and inherent phase-locking to the electron pulse, when the latter is generated by the same laser.

This fundamental interaction can also be used to study and demonstrate quantum photon-electron interaction. Photon-induced electron-microscopy (PINEM), first observed in 2009 and intended for applications in microscopy [3], has since evolved to be a fruitful source of photon-electron quantum phenomena. In particular, the free electron’s energy spectrum can be measured and shown to have discrete energy peaks, spaced with the interacting photon energy, and correlated to the number of photon exchanges that took place during the interaction.

In this seminar, I will introduce you to the field of DLA. I will discuss the general prospects of DLA beyond its initial goal - electron acceleration - and towards the rich physics of photon-electron interaction with nanostructures. Our recently-published demonstration of free-electron transport in a nanophotonic structure will be presented [4], along with results from our recently-submitted work on measurements of photon-energy-resolved energy peaks, which were measured in a scanning electron microscope for the first time [5].

1. J. Breuer and P. Hommelhoff, "Laser-based acceleration of nonrelativistic electrons at a dielectric structure," Phys. Rev. Lett. 111, (2013).

2. E. A. Peralta, K. Soong, R. J. England, E. R. Colby, Z. Wu, B. Montazeri, C. McGuinness, J. McNeur, K. J. Leedle, D. Walz, E. B. Sozer, B. Cowan, B. Schwartz, G. Travish, and R. L. Byer, "Demonstration of electron acceleration in a laser-driven dielectric microstructure," Nature 503, 91–94 (2013).

3. B. Barwick, D. J. Flannigan, and A. H. Zewail, "Photon-induced near-field electron microscopy," Nature 462, 902 (2009).

4. R. Shiloh, J. Illmer, T. Chlouba, P. Yousefi, N. Schönenberger, U. Niedermayer, A. Mittelbach, and P. Hommelhoff, "Electron phase space control in photonic chip-based particle acceleration," Nature 592, 498–502 (2021).

5. R. Shiloh, T. Chlouba, and P. Hommelhoff, "Quantum-coherent light-electron interaction in an SEM," Submitted arxiv.org/abs/2110.00764 (2021).

Note: the speaker is the candidate for the department

Quantum systems are remarkably sensitive to changes in their environment. This renders them extraordinary probes for sensing applications. In contrast to classical probes, they undergo transitions upon coupling that encode trajectory dependent quantum information in their statistics. Decoding this information requires a new set of inference methodologies, such as the one we introduce here.

Entangled photon pairs have inspired a myriad of quantum-enhanced metrology platforms, which outperform their classical counterparts. However, the role of photon exchange-phase and degree of distinguishability have not yet been utilized in quantum-enhanced applications. We show that when a two-photon wave-function is coupled to matter, it is encoded with “which pathway?” information even at a low degree of entanglement. An interferometric exchange-phase-cycling protocol is developed, revealing phase-sensitive information for each interaction history individually. Moreover, we find that quantum-light multimode interferometry introduces a new set of time variables that enable time-resolved signals, unbound by uncertainty to the inverse bandwidth of the wave-packet. We illustrate our findings on an exciton model-system and discuss future applications. 

Zoom link: https://us02web.zoom.us/j/9305767498?pwd=enFmcVg1UStqbEExbWUzSGhhdXNWdz…

In an attempt to provide further insight into one of the major questions of physics beyond the standard model, highly sensitive optomechanical sensors are developed utilizing techniques from the field of atomic physics. These sensors are table-top experimental tools offering exquisite control of mechanical, rotational and electrical degrees of freedom of optically levitated ~fg-ng masses in vacuum, enabling unprecedented acceleration and force sensitivities.

I will present two recent searches, the first looking for recoils from passing DM particles and the second for deviations from charge neutrality and so-called "millicharged particles". For certain, well-motivated dark matter models, these searches exceed the sensitivity of even large-scale experiments, thereby offering a complementary approach. I will also discuss possible techniques enabling sensor sensitivity to dark matter in the low-mass regime, where large, existing detectors lack in sensitivity.

Bound exotic systems offer unique opportunities to test our understanding of the tenets of modern physics and determine fundamental constants.

By comparing measured transitions between antihydrogen and hydrogen, we can search for CPT violation, which may explain the observed baryon asymmetry in the universe while respecting the stringent bounds on CP violation within the standard model.

The comparison of the energy levels of muonium (M) with their clean theoretical prediction searches for new physics in a multitude of scenarios, including new bosons coupled to leptons. Such particles are motivated by the persistent discrepancy between the recently remeasured anomalous magnetic moment of the muon and its theoretical prediction, arguably the most promising hint to new physics in decades.

In this talk I will review ongoing work for antihydrogen and M spectroscopy at CERN and PSI, and present our recent measurement of the Lamb-Shift in M, comprising an order of magnitude of improvement upon the state of the art and the first improvement to M energy levels in 20 years. I will conclude by showing that pushing M spectroscopy to its limits would independently determine the g-2 with enough accuracy to shed light on the puzzle.

The ability to control and manipulate free electrons is interesting for its fundamental aspects, while its development for imaging applications has seen great progress, enabling imaging at atomic resolutions. Recent developments in quantum information and quantum metrology have inspired a growing interest in developing techniques to control the quantum properties of free electrons, as well as attain the quantum limits for imaging applications. In this talk, I will describe a technique to control the quantum statistics of free electrons using ultrafast lasers, demonstrating a measurement of electron antibunching resulting from Heisenberg’s uncertainty and Pauli’s exclusion principles. I will then discuss progress towards realizing a quantum-inspired technique to enhance the dose efficiency of electron microscopes for imaging of single molecules with atomic resolution, as well as the quantum limits to phase contrast electron microscopy.

Note: the seminar will be given remotely over Zoom, on https://us02web.zoom.us/j/9305767498

N/A

The interaction of the electromagnetic field with matter gives rise to photonic quasiparticles: electromagnetic field excitations that have very different properties from photons in vacuum. When considering how these excitations are absorbed and emitted by electrons, one finds that these differences enable many phenomena that are difficult or even impossible to realize otherwise, promising a host of powerful technologies. In this talk, I will show as examples two of our recent results in this field.

First, I will show how photonic quasiparticles enable novel phenomena in scintillation, in which ionizing radiation converts its kinetic energy into photons. By integrating a scintillating material into a photonic crystal, we show experimentally how the scintillation can be strongly shaped and enhanced. Such nanophotonic scintillators provide a promising concept for low-dose and high-resolution imaging across many disciplines such as medicine, non-destructive inspection, and high-energy physics.

Second, I will introduce a mechanism called Fock lasing, by which a gain medium, undergoing stimulated interactions with a “sharply” nonlinear photonic quasiparticle, lases into a macroscopic Fock state of a cavity. We theoretically show several examples of how this mechanism may be implemented at optical and microwave frequencies, leading to approximate Fock states with up to thousands of photons, providing a path to extending the size of multi-photon Fock states by several orders of magnitude.​

Recording : https://biu365-my.sharepoint.com/:v:/g/personal/dallate_biu_ac_il/ESdHm…

How would our world look like if the fine structure constant $\alpha$ were of order unity? While in our small $\alpha$ world an atom excited to the first excited state has negligible probability of decaying to the ground state while emitting more than a single photon, such processes are important in a large $\alpha$ world, making photon frequency conversion effective in the single-photon regime. We show how such behavior can be realized in a superconducting circuit QED system, where a transmon, which serves as an artificial atom, is galvanically coupled to a high-impedance Josephson junction array, which acts as a waveguide for microwave photons with a high effective $\alpha$. Instantons (phase slips) that occur in the transmon interact with the microwave photons, and lead to inelastic scattering probabilities which approach unity and greatly exceed the effect of the quartic anharmoncity of the Josephson potential [1]. The instanton-photon cross section is calculated using a novel formalism which allows to directly observe the dynamical properties of the instantons, and should be useful in other quantum field theoretical contexts. The calculated inelastic decay rates compare well with recent measurements from the Manucharyan group at Maryland [2].

[1] Photon-instanton collider implemented by a superconducting circuit, A. Burshtein, R. Kuzmin, V. E. Manucharyan and M. Goldstein, Phys. Rev. Lett. 126 137701 (2021)

[2] Photon decay in circuit quantum electrodynamics, R. Kuzmin, N. Grabon, N. Mehta, A. Burshtein, M. Goldstein, M. Houzet, L. I. Glazman and V. E. Manucharyan, arxiv:2010.02099 (2020)

Recording: https://us02web.zoom.us/rec/share/C4Ae2pDdEfvFNDICX5kR8Nr3k6O8_Uu4uo8oG…

Ultracold atoms are a powerful resource for quantum technologies thanks to their unparalleled controllability. Floquet engineering is a powerful approach to implement novel effective Hamiltonians by employing periodic modulation. Such driving of a generic interacting many-body system eventually leads to heating. Still, at intermediate times, which are exponentially long with the driving frequency, the heating rate may be extremely low. During this time, the system assumes a prethemalized meta-stable state. Here we report on the first application of Floquet engineering with a strongly interacting Fermi gas in free space. Our engineered Hamiltonian is a flat potential for a mixture of two-spin states. It is created by an external magnetic field that counteracts most of the gravitational potential and concurrently the application of a rf field that induces a rapid spin rotation. We observe no heating on experimentally relevant timescales, when the driving frequency is high enough. In this regime, physical observables behave similar to those of a stationary gas at thermal equilibrium. In particular, we measure the pair-condensation fraction of a fermionic superfluid at unitarity and the contact parameter in the BEC-BCS crossover. The condensate fraction exhibits a non-monotonic dependence on the drive frequency and reaches a value higher than its value without driving. The contact parameter agrees with recent theories and calculations for a uniform stationary gas. Finally, we discuss possible routes to implementation of artificial gauge fields using Floquet engineering with a Fermi gases in the continuum.

Warm atomic vapors are known for their technical simplicity and potential scalability. However, despite these benefits, motional dephasing limits the strength and coherence of the light-matter interaction, as compared with laser-cooled atoms. I will present several schemes developed to realize strong, coherent, and faithful light-matter interaction at ambient conditions and to overcome motional dephasing, towards effective photon-photon interaction. These schemes can be further applied to various gas, solid and engineered systems hindered by inhomogeneous dephasing due to variations in time, space, or other domains.

First, I will describe a new protocol for an arbitrarily fast, genuinely noise-free, quantum memory in rubidium vapor. Employing a ladder level system of purely orbital transitions with nearly degenerate frequencies simultaneously enables high bandwidth, low noise, and long memory lifetime [1]. Second, I will present a scheme for protecting a qubit or a collective excitation from inhomogeneous dephasing. The scheme relies on continuously dressing the qubit with an auxiliary sensor state which exhibits an opposite and potentially enhanced sensitivity to the same source of inhomogeneity. We focus on motional dephasing of a spin-wave in an atomic ensemble. By employing a two-tone dressing field, we demonstrate complete suppression of inhomogeneous dephasing as well as immunity to drive noise [2]. In related works with continuous-wave spectroscopy, we demonstrate the enhancement and narrowing of spectral lines [3,4]. Finally, I will also present our effort to realize a unique optical mode by tapering down an optical fiber to the deep sub-wavelength scale.  This leads to a drastic expansion of the evanescent field to over 10 times the optical wavelength, compatible with typical dimensions of the Rydberg blockade. When interfaced with atomic vapor, this configuration balances tight confinement, long atomic interaction times, and negligible surface interactions [5]. 

[1] R. Finkelstein, E. Poem, O. Michel, O. Lahad, and O. Firstenberg, "Fast, noise-free memory for photon synchronization at room temperature", Science Advances 4 (2018).  

[2] R. Finkelstein, O. Lahad, I. Cohen, O. Davidson, E. Poem, and O. Firstenberg, “Continuous protection of a collective state from inhomogeneous dephasing”, Physical Review X 11 (2021) 

[3] O. Lahad, R. Finkelstein, O. Davidson, O. Michel, E. Poem, and O. Firstenberg, “Recovering the homogeneous absorption of inhomogeneous media”, Physical Review Letters 123 (2019) 

[4] R. Finkelstein, O. Lahad, O. Michel, O. Davidson, E. Poem, and O. Firstenberg, “Power narrowing: Counteracting Doppler broadening in two-color transitions”, New Journal of Physics 21 (2019) 

[5] R. Finkelstein, G. Winer, D. Z. Koplovich, O. Arenfrid, T. Hoinkes, G. Guendelman, M. Netser, E. Poem, A. Rauschenbeutel, B. Dayan, and O. Firstenberg “Super-extended nanofiber-guided field for coherent interaction with hot atoms”, Optica 8 (2021) 

Recording: https://biu365-my.sharepoint.com/:v:/g/personal/dallate_biu_ac_il/EXWcV…

Light offers a vast potential in the development of modern quantum technologies due to its intrinsic resilience to decoherence effects and its capacity to convey a huge amount of information. The many modes of light, would they be spatial modes or spectral modes, are as many quantum harmonic oscillators, leading to a largely unexplored Hilbert space[1]. In this talk, we will specifically consider the continuous variable approach, where the observables of interest are the quadratures of the electric field. 

We will first review how modal decomposition can be used to improve measurement sensitivity,  and reach the fundamental limits impose by the vacuum fluctuations in simple problems, as for instance estimating the separation of incoherent sources[2].

But continuous variables have also proven their worth as a platform for creating huge entangled states (entangling up to one million optical modes). Additionally, this entanglement can be created in a deterministic fashion and easily manipulated with standard techniques in optics. We will demonstrate how this can be achieve using time/frequency modes[3]. 

Finally, to reach a quantum advantage, and perform a task that cannot be efficiently simulated with a classical device, we require more than just entanglement. The additional ingredient is non-Gaussian statistics in the outcomes of the quadrature measurements. We will demonstrate how photon subtraction, a well know non-gaussian operation, can be rendered mode-dependent and allow for the generation of non-Gaussian multimode state of lights, required for quantum information processing[4].

[1] C. Fabre and N. Treps, Modes and States in Quantum Optics, Rev. Mod. Phys. 92, 035005 (2020).

[2] P. Boucher, C. Fabre, G. Labroille, and N. Treps, Spatial Optical Mode Demultiplexing as a Practical Tool for Optimal Transverse Distance Estimation, Optica, 7, 1621 (2020).

[3] J. Roslund, R. M. de Araújo, S. Jiang, C. Fabre, and N. Treps, Wavelength-Multiplexed Quantum Networks with Ultrafast Frequency Combs, Nature Photonics 8, 109 (2014).

[4] Y.-S. Ra, A. Dufour, M. Walschaers, C. Jacquard, T. Michel, C. Fabre, and N. Treps, Non-Gaussian Quantum States of a Multimode Light Field, Nature Physics 11, 1 (2019).

Quantum physics with light and mechanical oscillators already broke in various platforms the long-standing limitations of Gaussian states and linear interactions. Quantum non-Gaussian states of light and mechanical oscillators are generated with increasing quality and considered for applications. However, it is only the beginning of many possible journeys in this unknown and uncovered territory of physics where quantum noise combines with strong and exotic nonlinear effects. It is both challenging and stimulating investigation in tightly-connected theory and experiments. It is highly expected that these discoveries will bring unexpected quantum phenomena and applications of continuous-variable systems. The talk will present recent theoretical and experimental achievements in quantum non-Gaussian state preparation of photons and phonons and their diagnostics by new theoretical tools.

We will continue with the results in highly nonlinear physics with cubic nonlinearity for light and mechanical motion. The conclusion will address the next challenges of this exciting field.

(See attached pdf file)

Trapped ions are among the best-controlled quantum systems. However, for molecules, a similar degree of control currently lacks due to their complex energy-level structure. Quantum-logic protocols in which atomic ions serve as probes for molecular ions are promising for achieving this level of control. Here, I will describe our experimental results in achieving >99% fidelity in the quantum-nondemolition state detection of the nitrogen ion's electronic, vibration, and rotation ground state [1], thus making a crucial step towards the coherent manipulation of molecular quantum states. We further exploited our quantumlogic protocol for hyperfine and Zeeman resolved state identification and preparation in a complex region of the molecular spectrum, mimicking the situation encountered with polyatomic molecules [2].
The quantum control of rotation and vibration of molecules will significantly enhance the precision of molecular spectroscopy. It will open up opportunities for creating new time standards in the THz domain [3], searching new physics such as possible time variation in the proton-to-electron mass ratio, and encoding quantum information in molecular qubits at
telecom frequencies for quantum-communication applications.

[1] Sinhal, ZM, Najafian, Hegi, Willitsch, Science 367, 1213 (2020).
[2] Najafian, ZM, Sinhal, Willitsch, Nat. Commun. 11, 4470 (2020).
[3] Najafian, ZM, Willitsch, Phys. Chem. 22, 23083 (2020).
[4] ZM, Hegi, Najafian, Sinhal, Willitsch, Faraday Discuss. 217, 561 (2019).

Photons play a unique role as carriers of quantum information. They are essentially the only candidate on any scale: from linking neighboring qubits in quantum computers to a satellite-based quantum-key distribution [1].

My talk considers a different fundamental particle as a carrier of quantized information – the free-electron [2]. Although the electron mass renders energy and momentum exchanges of electrons and photons inefficient in free space, I propose a roadmap for reaching strong coupling between them by confining the photons to whispering-gallery-mode (WGM) microresonators. I describe possible quantum entanglements between the two entities, explain how it could be measured, and show experimentally the merits of WGM for controlling the electron state [3].

Aside from bringing free-electrons into the realm of quantum optics, the tight focusing of electron beams may allow for versatile access to individual quantum systems at the nanoscale. More generally, detailed control of electron-light interactions could enhance the capabilities of electron microscopy, which is already at the forefront of scientific research of the nanoworld.

[1]        J. Yin, et al., Satellite-Based Entanglement Distribution over 1200 Kilometers, Science 356, 1140 (2017).

[2]        O. Kfir, Entanglements of Electrons and Cavity Photons in the Strong-Coupling Regime, Phys. Rev. Lett. 123, 103602 (2019).

[3]        O. Kfir, et al., Controlling Free Electrons with Optical Whispering-Gallery Modes, Nature 582, 7810 (2020).

Free-electron beams in dedicated electron microscopes are an extremely functional probe for microstructure and composition [1], reaching a spatial resolution below an Angstrom. Optical control of the electrons in such microscopes facilitates ultrafast and ultrasensitive imaging and spectroscopy modalities. However, the weak coupling of electrons with photons is a limiting factor for emerging applications [2,3] of light-based electron control.

This talk demonstrates the merits of combining two scientific paradigms: electron microscopy and optical cavities. In particular I focus on whispering gallery mode (WGM) cavities for an efficient coupling to relativistic free-electrons [4,5]. I show how basic features of WGMs, such as light storage, modal population, and light coupling are expressed in the interaction with electrons. Importantly, an optimized arrangement of microresonators drives an unprecedented modulation of the electron beam, expressed as a broad and coherent electron-energy spectrum, including hundreds of sidebands [5]. In the future, the strong-coupling of electrons to resonant traveling modes can be used for fundamental electron-photon research, such as entangled electron-photon pairs, optical electron-phase manipulation, and generally, the merging of electrons into the realm of quantum optics. Furthermore, the combination of resonators with electron microscopy allows for dynamical imaging and spectroscopy with nanometer resolution and a temporal resolution down to the attosecond-scale.

1. Krivanek et al., Nature 464, 571–574 (2010)

2. Priebe, et al., Nature Photonics 11, 793–797 (2017).

3. Schwartz et al., Nature Methods 16, 1016–1020 (2019)

4. Kfir, Phys. Rev. Lett. 123, 103602 (2019)

5. Kfir et al., Nature 582, 46–49 (2020)

Mini-series of zoom lectures on

“Quantum simulations with superconducting qubits”

Quantum computers made of superconducting qubits offer a novel paradigm of driven many-body quantum systems. The key strength of this platform is the possibility to tune and measure each qubit individually. But they also have important limitations, such as their digital approach, associated with their future goal of solving complex quantum information algorithms. This series of talks will review some recent experiments aimed at using digital quantum computer to simulate interesting many-body effects.

Please register at http://tiny.cc/biuoptics

Mini-series of zoom lectures on

“Quantum simulations with superconducting qubits”

Quantum computers made of superconducting qubits offer a novel paradigm of driven many-body quantum systems. The key strength of this platform is the possibility to tune and measure each qubit individually. But they also have important limitations, such as their digital approach, associated with their future goal of solving complex quantum information algorithms. This series of talks will review some recent experiments aimed at using digital quantum computer to simulate interesting many-body effects.

Recorded lecture  : https://biu365-my.sharepoint.com/:v:/g/personal/dallate_biu_ac_il/Ed4Xq…

Mini-series of zoom lectures on

“Quantum simulations with superconducting qubits”

Quantum computers made of superconducting qubits offer a novel paradigm of driven many-body quantum systems. The key strength of this platform is the possibility to tune and measure each qubit individually. But they also have important limitations, such as their digital approach, associated with their future goal of solving complex quantum information algorithms. This series of talks will review some recent experiments aimed at using digital quantum computer to simulate interesting many-body effects.

Link to the recorded lecture: https://biu365-my.sharepoint.com/:v:/g/personal/dallate_biu_ac_il/ESpX1…

Mini-series of zoom lectures on

“Quantum simulations with superconducting qubits”

Quantum computers made of superconducting qubits offer a novel paradigm of driven many-body quantum systems. The key strength of this platform is the possibility to tune and measure each qubit individually. But they also have important limitations, such as their digital approach, associated with their future goal of solving complex quantum information algorithms. This series of talks will review some recent experiments aimed at using digital quantum computer to simulate interesting many-body effects.

Recorded lecture: https://biu365-my.sharepoint.com/:v:/g/personal/dallate_biu_ac_il/EZbK-jei655Fq4D680mn1JUB8ux_JD4Df8KKphqXrPM3Bw?e=WiCcM7 .

When an excitonic material is placed inside a resonant optical cavity, the quantum-coherent interaction with light can give rise to formation of composite light-matter excitations known as polaritons. Although polaritonic systems have been studied for many years in the context of optics, recent advances show that such coupled system offer exciting opportunities to affect the properties of the material itself. I this talk I will discuss some of our recent results under this topic, focusing on transport phenomena and how they can be controlled by coupling the material to photonic structures.

Why control mechanics at the quantum level?

First and foremost, placing macroscopic objects in superposition states has captured the imagination and interest of physicist for over a century. Today, at 2019, researchers are able to fulfill some of these dreams and gendanken experiments with bigger and bigger objects (heavier, larger and involving more atoms). On a log scale, we moved from controlling the mechanical motion of a single atom (~10-100 x 10^-27 Kg) to controling the collective motion of 10^12 atoms (~ 50 pg) or more. Mechanical quality factors of various systems have been improving, from 10^5-10^6 to more than 10^9,  in the past 5 years alone (!). Since no inherent obstacle has been found to prohibit quantum mechanical control of even larger objects, the quest goes on. 

Second, engineered mechanical systems stand out also in the context of Quantum Information Processing. They can be compact, and easily fabricated. Their good quality factors means they are good quantum memories. They can accommodate multiple transduction mechanisms (electric, magnetic, piezo-electric etc.). Finally, because their frequency can be very different than their environment resonances, mechanical elements can decouple from the outside world, and couple only when needed. 

1. What kind of resources are needed to generate non-classical states. Specifically I will talk about membrane to ion coupling (resonant), superconducting qubit to mechanical drum coupling (dispersive) and superconducting resonator to mechanical drum(s) (parametric).

2. Why verifying that indeed the state is non-classical is important and in some cases takes most of the work. Here we will focus on the Simon-Duan criteria for Gaussian states, when we analyze entangled states of two mechanical drums.

TBA

Photons are a potential resource for a growing host of applications in quantum technologies and quantum information sciences. A particular interest is in effectively harvesting pure single photons from simple quantum emitters, and in finding effective ways for strong interactions between only a few photons. 

Nir Davidson

Dept. of Physics of Complex Systems, Weizmann Institute of Science, Rehovot, Israel

We investigate phase locking of large arrays of coupled lasers in a modified degenerate cavity (MDC). We show that the minimal loss lasing solution is mapped to the ground state of an XY spin Hamiltonian with the same coupling matrix provided the intensity of all the lasers is uniform. We study the probability to obtain this ground state for various coupling schemes, system parameters and topological constrains. We demonstrate the effect of crowd synchrony with a sharp transition into an ordered state above a critical number of coupled lasers. Finally, we present recent results demonstrating the ability of our system to solve related problems such as phase retrieval, imaging through scattering medium and more.

The Quantum Information Science Center at the Hebrew University of Jerusalem has won a NIS 7.5 million tender from the Government of Israel to build a deployable demonstration of a Quantum Key Distribution (QKD) system. In this talk I will first present what is a QKD system, why might it be needed, and what our efforts, goals and accomplishments have been to this end. Our work is set to position Israel among the selective club of nations with such a technology and research infrastructure.

I will also present shortly the work of researchers at Hebrew University and other members of our consortium to establish this homegrown infrastructure.

Entanglement generation is a crucial ingredient for the realization of future quantum technologies, and requires high fidelity quantum gates between atomic and photonic qubits. I will describe the novel concept of quantum metasurfaces which allows for the generation of large-scale atom-photon entanglement, hence constituting a new platform for manipulating both classical and quantum properties of light. These quantum metasurfaces are realized by preparing and manipulating entangled states of atomic arrays which scatter or emit light. I will show that this platform allows for multi-qubit gates between atomic and photonic qubits, and for the generation of photonic GHZ states and highly entangled states suitable for quantum information processing. I will discuss potential experimental realizations and possible new applications. Finally, I will describe a new experimental effort to realize large-scale entanglement with quantum defects in a nanophotonic environment.

[3]         O. Kfir,  et. al., Sci. Adv. 3, eaao4641 (2017).

Interactions of molecules with light play a fundamental role in nature, where photons usually act on the molecules and drive chemical reactions and other processes. However, when confined to sub-wavelength regions, the interaction with light can be enhanced up to the point where the quantum-coherent interactions overcome all other processes. In this "strong coupling" regime the photons and the material start to behave as a single entity, having its own quantum states and energy levels. In my talk I will present the fundamental physics of strong coupling in hybrid photonic-molecular structures, and how such cavity-QED effects can be used in order to control material properties and chemical processes in molecules.

Precision measurements in atomic and molecular systems are complementary to studies with high-energy colliders in searches for physics beyond the standard model. Among these are measurements of permanent electric dipole moments (EDMs) of elementary particles, such as the electron, which constitute a low background probe of CP violation. The quantum state preparation and detection techniques developed for precision measurements with molecules may prove to be useful for a variety of applications ranging from quantum chemistry to quantum simulation.

In the second-generation measurement of the eEDM using trapped HfF⁺, the statistical uncertainty is projected to be competitive at 2 x 10⁻²⁹ e cm in one hour of integration time. To this end, we have attained a 2.5 second spin coherence time, and a 20-fold increase in count rate via optical pumping into states of opposite molecular orientation. We suppress technical noise by conducting a differential measurement of spatially separated photofragments arising from opposite molecular orientations, reaching the quantum projection noise limit. We will also discuss the progress towards a future measurement with ThF⁺molecules, where minute long spin precession times are predicted. By multiplexing these measurements, we project an overall 100-fold increase in sensitivity to the eEDM.

Quantum fluctuations of light impose a fundamental limit precision optical measurements, laser interferometric detection of gravitational waves (GWs), for example. Current generation GW detectors are limited by quantum noise and plan to improve their sensitivity by injecting squeezed states of light generated by non-linear optical materials. We present an alternative technology for producing squeeze states of light using the radiation pressure interaction of light with a mechanical oscillator. Such optomechanical (OM) squeezed light sources would be widely applicable for future precision measurements because their non-linearity is independent of the laser wavelength. Previously, OM squeezers were limited to cryogenic temperatures. I will present our recent measurement of squeezed light from an OM system at room temperature [1]. Operation of a quantum OM system at room temperature not only makes its integration into complex interferometers more feasible, it also provides a resource for exploring quantum light-matter interactions in a human-perceivable environment.

[1]: https://arxiv.org/abs/1812.09942   

It is yet unclear whether even ideal analog quantum machines can perform computational tasks faster than their classical counterparts. I will discuss the results of several recent studies that suggest the existence of several fundamental limiting factors to, as well as a couple of promising directions for, physical analog quantum devices.

The study of quantum many-body spin physics in realistic solid-state platforms has been a long-standing goal in quantum and condensed-matter physics. We demonstrate separate steps required to reach this goal using NV centers in diamond. First, standard (TEM) electron irradiation is used for the enhancement of N to NV conversion efficiencies by over an order-of-magnitude [1]. Second, robust pulsed [2] and continuous [3] dynamical decoupling (DD) techniques enable the preservation of arbitrary states of the ensemble. These combined efforts, which already resulted in the demonstration of enhanced magnetic sensing [4], could lead to the desired interaction-dominated regime. Finally, we simulate the effects of continuous and pulsed microwave (MW) control on the resulting NV-NV many body dynamics in a realistic spin-bath environment [5]. We emphasize that dominant interaction sources could be identified and decoupled by the application of proper pulse sequences, and the modification of such sequences could lead to the creation engineered interaction Hamiltonians. Such interaction Hamiltonians could pave the way toward the creation of non-classical states, e.g. spin-squeezed states, which were not yet demonstrated in the solid-state, and could eventually lead to magnetic sensing beyond the standard quantum limit (SQL).

[2] D. Farfurnik et al., Phys. Rev. B 92, 060301(R)

[3] D. Farfurnik et al., Phys. Rev. A 96, 013850

[4] D. Farfurnik, A. Jarmola, D. Budker and N. Bar-Gill, J. Opt. 20, 024008

[5] D. Farfurnik, Y. Horowicz and N. Bar-Gill, Phys. Rev. A 98, 033409 

Photonic limiters are protection devices which transmit electromagnetic radiation at low-level incident intensity while blocking high-intensity electromagnetic signals. Passive limiters typically block excessive radiation by means of absorption, which can often cause their destruction due to overheating. We propose the design of a reflective limiter based on resonant transmission through a defect localized mode. The benefit of this design is that it offers protection by reflecting the excessive radiation instead of absorbing it, which reduces overheating problems and results in a device with an extended dynamic range. In this talk, I will present implementations of this idea in band-gap systems in (i) the infrared domain, based on multilayer photonic crystals, and (ii) the microwave domain, based on chiral or CT symmetric coupled resonator waveguide arrays.

Hawking radiation, the quantum emission of light from black holes, is too weak to be measured from known astrophysical sources. However, experimental observations can be made in laboratory settings using analogue systems. In such systems, the space-time geometry of the event horizon is mimicked by a moving medium.

In this talk, I will present recent experimental observations of
a stimulated Hawking effect from a fiber optical analogue of the event horizon. In our experiment, a few-cycle laser pulse traveling in a highly nonlinear optical fiber creates an effective moving medium. As a result, probe light traveling with similar group velocity experiences an event horizon.

We observe the scattering of the probe by the pulse into positive and negative frequency modes. These frequencies are exactly the frequencies that will be spontaneously emitted when the probe is the quantum vacuum. This study paves the way for the observation of spontaneous Hawking radiation and related phenomena.

Coming out of a hot oven, a trapped ion can be cooled by light down to a thousandth degree above Kelvin just by applying radiation pressure. Despite this reality, existing theories of the cooling dynamics are mostly limited to the final stage of the cooling where the time-dependence and anharmonicity of the trap can be neglected. I will present a semiclassical framework based on action-angle phase-space coordinates, that advances the understanding of laser cooling dynamics far from thermal equilibrium. Using this approach we analyze different regimes of motion resulting from the combination of a time-dependent trap drive and laser damping, which can lead to the capture of a particle in large-amplitude, stochastic limit cycles. At the same time, trapped-ion experiments are well suited also for studying many-body driven-dissipative dynamics. Within one- and two-dimensional crystals of trapped ions, the electronic states forming a two-level system (equivalent to a spin-1/2) of different ions, can be coupled using light. When strongly driven and at the presence of dissipative processes, interacting spins form a fundamental model of nonequilibrium dynamics, which describes also solid-state systems such as superconducting circuits coupled to an array of light cavities. I will present an ongoing study focusing on the role of quantum correlations in determining the system's phase beyond the meanfield limit, and how the phases and dynamics depend on the dimension, the interaction, and other system parameters.  

Attosecond science is based on steering electrons by the electric field of a strong laser pulse. It has enabled the observation of electron dynamics in atoms, molecules and solids on its natural time scale, the attosecond domain (1as = 10-18s). In my talk, I will show that attosecond science can be extended to the nano-scale, opening up a new perspective for nanoscience and ultrafast spectroscopy. In a pioneering experiment, we demonstrate that electron emission from a metallic nanostructure can be controlled by the waveform of the electric field of a laser pulse. Depending on the absolute phase of the pulse, high-energy electrons are emitted within one or two time windows of attosecond duration. We also show how strong-field-driven photoemission can be used to sense electric fields with attosecond and nanometer resolution, providing new tools for nano-optics and nonlinear optics. Our research bears the prospect of realizing lightwave electronics, where a laser field can induce and control electric currents at optical (PHz) frequencies.

How do atoms radiate together? Although still an open question in general, addressing this problem of collective light-matter interactions in specific cases can lead to important insights and applications. In my talk, I will discuss how the collective optical response of a 2D array of trapped atoms renders it as a new platform for quantum science, with potential applications in quantum technologies. In particular, I will show how a dilute 2D array, comprised of even just a few dozen atoms, can perfectly reflect and scatter light, leading to the possibility of observing for the first time opto-mechanical phenomena at the single-photon level. I will discuss how this may pave the way towards the realization of “quantum metamaterials” which can exhibit a quantum superposition of their macroscopic optical responses. 

Exceptional points (EPs) are exotic degeneracies in non-Hermitian systems. Due to their counterintuitive properties and recent realizations, EPs have been the focus of immense attention. In this talk, I will present three new applications of EPs: (I) Enhancing spontaneous emission (SE) near EPs [1-3], (II) controlling atomic and molecular absorption [4], and (III) creating topological mode switches using open quantum systems.  I will begin by presenting our formula for the SE spectrum near EPs, where standard mode-expansion methods lead to erroneous and divergent results. I will further show that significant SE enhancements can occur in systems with gain (exceeding 400×).   In the second part of the talk, I will present a method for optically inducing EPs in atomic systems, and show that slight changes in the laser parameters may lead to either dramatic enhancement or to complete inhibition of the absorption. Finally, I will describe the intriguing properties of topological mode switches in open quantum systems. When varying a system slowly along a closed path, an adiabatic system returns to its initial state - unless the path encircles an isolated EP, in which case the initial and final states switch. However, non-Hermitian systems do not always evolve adiabatically, and the outcome of the switch depends on the chirality of the path. We explore asymmetric mode switching in open quantum systems, which offer a rich EP structure, including high-order isolated and embedded EPs.

[1] A Pick, B Zhen, OD Miller, CW Hsu, AW Rodriguez, M Soljacic, and SG Johnson, “General theory of spontaneous emission near exceptional points,” Opt. Express. 25, 12325 (2017)

[2] Z Lin, A Pick, M Loncar, and AW Rodriguez, Inverse design of third-order Dirac exceptional points in photonic crystals. Phys. Rev. Lett. 117, 107402 (2017)

[3] A Pick, Z Lin, and, AW Rodriguez, “Enhanced nonlinear frequency conversion and Purcell enhancement at exceptional points,” Phys. Rev. B 96, 224303 (2017)

[4] A Pick, PR Kapralova-Zdanska, and N Moiseyev, “Optical absorption in atoms and molecules near laser-induced exceptional points,” arXiv: 1809.02868 (2018)

Studies of technologies based on quantum systems have gained immense importance in recent years, owing to the current experimental progress in control of quantum systems. I will talk about technologies based on open quantum systems. I will show how efficiencies of quantum heat engines powered by squeezed thermal reservoirs can surpass the Carnot limit, without violating the second law of thermodynamics. I will also talk about dynamical control of quantum systems, which can lead to quantum advantage in quantum heat machines, as well as enable us to perform high-precision low-temperature thermometry close to the absolute zero. 

We are living in the Quantum Era. Quantum features, such as entanglement, have enabled the discovery of many exciting phenomena, and are now being exploited in the development of futuristic technologies. Quantum computing and quantum communications are only two of the foreseen applications. Furthermore, cutting-edge experiments are being proposed to operate in regimes where relativity plays a role. In such situations, relativity is included as an ad-hoc modification of the standard Schrödinger equation. Regardless of the advances within their respective domains, relativity and quantum mechanics are fundamentally incompatible. It is an open question how to properly describe and characterise quantum technologies in regimes where relativity is important.

In this work we give an overview of the recent progress in the field of relativistic quantum information, focusing on the role of quantum correlations in relativistic and quantum science. We focus on the role correlations play in small, localised quantum system and discuss how they can be exploited to extract information about relativistic properties of such systems. This allows us to uniquely identify relativistic contributions to a plethora of measurements, which can lead high-precision measurements of relativistic parameters. We conclude with a discussion on potential implementations in Bose-Einstein Condensates and optomechanical systems.

 

Causal inference is a (classical) technique used to figure out what sorts of causal relationships between variables constitute a viable explanations for some observed statistics. Equivalently, causal inference allows us to quantify the sorts of correlations between variables which are possible given a particular causal structure. The famous inability to explain quantum correlations in terms of local hidden variable models can be understood as a fact about causal inference, namely: whereas in classical causal structures all unobserved variables have the status of shared randomness, in quantum causal structures an observed system can represent quantum entanglement. Accordingly,  Bell's theorem can be recast in causal terminology: The set of correlations compatible with a (particular) quantum causal structure strictly contains the set of correlations compatible with its analogous classical causal structure. I'll set out a series of research targets related to generalizing this quantum-advantage to network-like causal structures; focusing mostly on the simplest networks, consisting of three parties sharing pairwise entanglement. Based mostly on arXiv:1609.00672.

Tags: Quantum Foundations, Quantum Internet, Causal Inference, Causal Structure, Triangle Scenario, Inflation Technique

Diffusion in Translucent Media

Azriel Z. Genack, 
Department of Physics, Queens College and
Graduate Center of the City University of New York, Flushing, New York 11367

Diffusion is the result of repeated random scattering. It governs a wide range of phenomena from Brownian motion, to spin transport in magnetic materials, electronic conduction, heat flow through window panes, neutron flux in fuel rods, and the dispersion of light in human tissue. It is universally acknowledged that the diffusion model fails in translucent samples thinner than the mean free path in which waves propagate ballistically. We show in optical measurements and numerical simulations that the scaling of transmission and the profiles of average intensity for random illumination and for excitation of transmission eigenchannels have the same form in translucent as in opaque media [1]. Paradoxically, the robustness of the diffusive character of steady-state transport in thin samples explains puzzling observations of suppressed optical and ultrasonic delay times relative to predictions of diffusion theory well into the diffusive regime. The source for the common characteristics of propagation in translucent and diffusive media is the shared statistics of transmission eigenvalues.

Reference

[1] Z. Shi and A. Z. Genack, Nature Comm. 9, 1862 (2018).

In the past decades optical fibers have become the main medium through which information is transmitted. Unlike most other forms of communications, the mechanism that puts an ultimate limit on the achievable data transmission rates in fibers is the optical nonlinearity, and hence its modeling is of utmost importance to the advancement of the field. The talk will review the ways in which nonlinear optical mechanisms affect the performance of modern communications systems, and present approaches for managing the nonlinear phenomena, as well as to the communications limits that can be expected in their presence.

A nonlinear SU(1,1) interferometer is a sequence of two coherently pumped high-gain parametric amplifiers, realized through parametric down-conversion or four-wave mixing. The radiation emitted by the first amplifier can be amplified or deamplified in the second one, depending on the phase shifts acquired on the way. This makes the interferometer extremely sensitive to phase shifts, its sensitivity reaching the Heisenberg limit in the lossless case.

Losses certainly reduce the phase sensitivity; however, detection loss can be overcome by making the interferometer gain-unbalanced. As we have shown theoretically [1] and experimentally [2], phase sensitivity below the shot-noise level can be achieved even with very inefficient detection provided that the second amplifier is pumped sufficiently strong.

In my talk I will consider different constructions of an SU(1,1) interferometer based on high-gain parametric down-conversion. In particular, by imaging one parametric amplifier on the other one, the interferometer is made not sensitive to the radial mode content. Such a construction can be applied to sensing of orbital angular momentum perturbations.  

[1] M. Manceau et al., New Journal of Physics 19, 013014 (2017).

[2] M. Manceau et al., Phys. Rev. Lett. 119, 223604 (2017).

Pmetric-down conversion (PDC) has been studied extensively at optical wavelengths. The extension of this effect into X-ray wavelengths offers many advantages due to the high spatial resolution and the extremely low noise of commercial X-ray detectors. My talk comprises of two such applications:

1. Parametric-Down Conversion of X rays into the Optical Regime

Nonlinear interactions of X-rays and optical radiations can provide insight into the microscopic structure of chemical bonds and the valence electron density of crystals and into light-matter interactions at the atomic-scale resolution [1]. We observe parametrically down converted X-ray signal photons that correspond to idler photons at optical wavelengths for the first time [2]. The results demonstrate a new method for probing valence-electron charges and microscopic optical responses of crystals at the atomic-scale resolution.

2. Ghost imaging of X ray paired photons

PDC is one of the major sources for the generation of non-classical states of light. This type of radiation is extensively used to study numerous quantum phenomena at optical wavelengths. Despite the potential for research with X-rays, no application of X-ray PDC generated pairs has been reported. We observe ghost imaging by using parametrically down-converted X-ray photon pairs [3]. We reconstruct the images of slits with nominally zero background levels. Our procedure can lead to the observations of many quantum phenomena at X-ray wavelengths.

References

[1] I. Freund and B. F. Levine, Phys. Rev. Lett. 25, 1241 (1970).

[2] A. Schori, C. Bömer, D. Borodin, S. P. Collins, B. Detlefs, M. Moretti Sala, S. Yudovich, and S. Shwartz, Phys. Rev. Lett., 119, 253902 (2017).

[3] A. Schori, D. Borodin, K. Tamasaku, and S. Shwartz, Phys. Rev. Lett., submitted (2018)

The first successful practical implementation of a total reflection zone plate (RZP) as a monochromator-spectrometer at the femto-slicing synchrotron radiation beamline was done in 2008 [1]. The 20 times higher transmittance and a pulse elongation on the order of 30 fs with an energy resolution similar to a conventional plane grating monochromator beamline attract many in-house and external users to perform their high-ranking experiments at the BESSY II facility. In 2014, the beamline was upgraded and presently can cover an energy range of 300 eV to 1200 eV continuously, with parallel recording of XANES spectra of elements with a time resolution down to ~ 100 fs [2].

The principle of a combination of three functions in one optical element (reflection, energy dispersion and focusing) was extended for the development of a new generation of spectrometers for fs-spectroscopy on highly diluted materials [3], fs monochromators for high harmonic generators (HHG) [4], and laser-plasma X-ray sources [5].

In the class of laboratory instrumentation, the multi-channel RZP fluorescence spectrometer for the scanning electron micro- scope has shown unique performances in the energy range of 40 eV to 1000 eV [6].

In this talk, also reported on a new type of a time-delay compensated monochromator (TDCM) with a pulse elongation below 5 fs at the photon energy of 450 eV, continuously tuning in the energy range of 100 eV – 1000 eV.

References

[1] A. Erko et al., AIP Conference Proceedings 1234, (2010) 177.

[2] K. Holldack, et al., Journal of Synchrotron Radiation, 21, (2014) 1090.

[3] R. Mitzner et al., The Journal of Physical Chemistry Letters, 4, (2013) 3641.

[4] J. Metje et al., Optics Express, 22(9), (2014), 10747.

[5] I. Mantouvalou et al., Applied Physics Letters, 108, (2016) 201106.

[6] A. Hafner et al., Optics Express, 23(23), (2015) 29476.

Guided Acoustic Waves Brillouin Scattering (GAWBS) is a non-linear optical effect, in which two co-propagating optical waves that are detuned by specific frequency offsets stimulate guided acoustic waves of an optical fiber or waveguide. The frequency of the stimulated acoustic wave equals the detuning between the two optical frequencies, and its axial phase velocity matches the phase velocity of light in the waveguide. An additional optical wave that co-propagates in the same waveguide becomes affected by phase-matched photo-elastic perturbations and undergoes phase modulation at the acoustic wave frequency.

In standard optical fibers, the acoustic waveguide is the entire silica rod (usually of 125 µm diameter), whereas the optical waveguide is an 8 µm core on the axis of symmetry. This difference in dimensions reduces the efficiency of opto-mechanical coupling. At the same time, however, opto-mechanical interaction in fibers exhibit unique characteristics: while the stimulating optical waves never leave the core, the generated acoustic waves profiles span the entire cross-section of the fiber. In this seminar we will discuss the physics involved in the GAWBS process in optical fibers, and present two of its possible applications demonstrated by our research group in the last few years:

1. Distributed opto-mechanical sensing: GAWBS enables sensing of mechanical properties of an analyte outside the cladding of uncoated standard optical fiber. Recently, we were able to extend the capabilities of our sensing platform from a single-point measurement, to a distributed mechanical impedance sensing. First results distinguish between water and ethanol over 3km of standard single mode fiber with 100m resolution. Such measurements allow us to "listen", where we may not "look", as guided light never leaves the core of the fiber and does not "see" the medium under test. Measurements are also perfromed outside coated fibers.
2. A "phonon laser" over a multi-core fiber: Narrowband acoustic oscillations can be obtained through the introduction of feedback to the acoustic wave, in so-called "phonon lasers". In the current research of our group, stimulated emission of highly-coherent, guided acoustic waves is achieved based on inter-core, opto-mechanical cross-phase modulation in a commercial multi-core fiber, at room temperature. The fiber is connected within an opto-electronic cavity loop. Pump light in one core is driving acoustic waves via electrostriction, whereas an optical probe wave at a different physical core undergoes photo-elastic modulation by the stimulated acoustic waves. Single-frequency mechanical oscillations at hundreds of MHz frequencies are obtained. The linewidths of the acoustic waves oscillations are on the order of 100 Hz, orders of magnitude narrower than those of the pump and probe light sources. The results can pave the way towards practical phonon laser sources, for applications in sensing, metrology, information processing and more.

Quantum error correction allows quantum computers to operate despite the presence of noise and imperfections. A critical component of any error correcting scheme is the mapping of a quantum error syndrome onto an ancilla qubit. However, errors occurring in the ancilla can propagate through the mapping operation onto the logical qubit, and irreversibly corrupt the encoded information. A fault-tolerant measurement protocol, which prevents the occurrence of such uncorrectable errors, is therefore a prerequisite for scaling up quantum error correction. 

I will present our recent demonstration of the fault-tolerant measurement of an error syndrome on a logical qubit encoded in a superconducting cavity. We achieve fault tolerance hardware-efficiently by coupling the logical qubit to a single multilevel ancilla transmon. The cavity-ancilla interaction is modified in-situ using off-resonant sideband drives to make the logical qubit transparent to all first-order ancilla errors. We achieve a sevenfold increase in the average number of syndrome measurements performed without destroying the logical qubit. These results demonstrate that hardware-efficient approaches which exploit system-specific error models can yield important advances towards fault-tolerant quantum computation.

Interactions between optical fields and physical devices are extremely fast yet incredibly complex and thus naturally exhibit an immense capacity for information that is well beyond what is possible using conventional hardware (e.g. electronics). Here I will discuss our work on harnessing this unrivaled information capacity to enable photonic systems for imaging and information security that outperform traditional limits. Specifically, I will discuss our work on harnessing volumetric optical scattering to create miniscule compressive optical imagers that operate with a sub-Nyquist number of measurements. Additionally, I will discuss our work on harnessing ultrafast nonlinear interactions in silicon photonic micro-cavities to realize photonic physical unclonable functions (PUFs), which are physical keys that cannot be copied or emulated. These PUFs have applications as unique sources of key material for information and hardware security.

The nanoscale processes by which UV irradiation initiates damage in biological material have not yet been fully elucidated. This represents a barrier to innovations in radiotherapy and also limits our understanding of the molecular origins of life. Experiments on gas-phase biological building blocks can reveal detailed information via comparisons with high-level calculations, while parallel studies of biomolecular clusters offer a route to assess the effects of condensed biological environments. In forthcoming optics talk in Bar Ilan University, I will mainly focus on the stabilities and relaxation pathways of isolated and clustered nucleobases in neutral electronic excited states and ionic states. Furthermore, I will report a new laser thermal desorption facility and also reports advances in applying Stark deflection to narrow the range of molecular and cluster configurations in continuous supersonic beams.

Quantum artificial intelligence (AI) is an interdisciplinary field, which has emerged in the last five years with the promise of enhancing AI performances. The first part of the talk will focus on reinforcement learning (RL), in which learning is achieved via interactions with a rewarding environment. Following an introduction to a classical-RL model we developed [1] and a short review of our work on discrete quantum walks [2-3], I will present a quantum-RL model that we constructed, which constitutes the first example of RL model that employs quantum processes. The model, which is based on incorporating quantum walks into the agent’s “memory scheme”, exhibits a proven quadratic speedup over its classical counterpart in terms of the agent's ‘’thinking time’’ [4].

In the second part of the talk I will establish a connection between entanglement detection and the NPcomplete satisfiability problem (SAT): I will prove that having the capacity to (efficiently) determine if a pure state is entangled implies an efficient solution to the SAT problem [5].

[1] A. Makmal, A. A. Melnikov, V. Dunjko, H. J. Briegel, “Meta-learning within Projective Simulation”, IEEE ACCESS, 4, 2110, 2016.

[2] A. Makmal, M. Zhu, D. Manzano, M. Tiersch, H. J. Briegel, “Quantum walks on embedded hypercubes”, Phys. Rev. A, 90, 022314, 2014.

[3] A. Makmal, M. Tiersch, C. Ganahl, H. J. Briegel, “Quantum walks on embedded hypercubes: Non-symmetric and non-local cases”, Phys. Rev. A, 93, 022322, 2016.

[4] G. D. Paparo, V. Dunjko, A. Makmal, M. A. Martin-Delgado, H. J. Briegel, “Quantum speedup for active learning agents”, Phys. Rev. X, 4 (3), 031002, 2014.

[5] A. Makmal, M. Tiersch, V. Dunjko, S. Wu, “Entanglement of π–locally-maximally-entangleable states and the satisfiability problem”, Phys. Rev. A 90 (4), 042308, 2014.

Total internal reflection fluorescence (TIRF) microscopy and its variants are standard technologies for visualizing the dynamics of single molecules or organelles in live cells. Yet truly quantitative TIRF remains problematic. One unknown hampering the interpretation of evanescent-wave excited fluorescence intensities is the undetermined sample refractive index (RI). Here, we use a combination of TIRF excitation and supercritical angle fluorescence (SAF) emission detection to directly measure the average RI in the "footprint" region of a living cell during image acquisition. Our RI measurement is based on the determination on a back-focal plane image of the critical angle separating evanescent and far-field fluorescence emission components. We validate our method by imaging mouse embryonic fibroblasts and BON cells in culture. By targeting various dyes and fluorescent-protein chimeras to vesicles, the plasma membrane, as well as mitochondria and the endoplasmic reticulum, we demonstrate local RI measurements with subcellular resolution on a standard TIRF microscope, with a removable Bertrand lens as the only modification. Our technique has important applications for imaging axial vesicle dynamics, for determining the mitochondrial energy state or detecting metabolically more active cancer cells.

In my talk, I will present data combining near-membrane imaging and refractometry with organelle precision in live cells, I will discuss the interest of combining TIRF excitation and SAF on a single microscope in a type of "co-planar" geometry, and I will swiftly introduce a new geometry allowing simultaneous confocal TIRF and RI imaging with sub-diffraction spatial resolution that we are currently implementing. (martin.oheim@parisdescartes.fr)

The system of few identical fermions interacting resonantly with a distinguishable atom exhibits a rich and interesting physics, including universal states and the celebrated Efimov effect.

The (2+1) system, composed of two heavy fermions and lighter atom, supports a universal trimer state if the ratio of the particle masses exceeds critical value. For even larger mass ratio the system becomes Efimovian, introducing a three-body scale and showing geometric series of bound states.

Interestingly, this trend continues in the (3+1) system as well as in the (4+1) system, having their own universal states and pure (N+1)-body Efimov effects.

Quantum optics experiments employing a single photon source, as well as a single photon detector, allow us to probe the foundations of quantum theory. In the last few years I have designed a line of experiments based on weak measurements [1] for this purpose. Two of them have already been performed:

1. Measuring incompatible observables by exploiting sequential weak values [2] – We measured for the first time the polarization of single photons in two incompatible bases. By performing a sequence of two weak measurements over a large ensemble of single photons, we were thus able to infer the information regarding two noncommutative operators, practically measured on the same state.
2. Determining the quantum expectation value by measuring a single photon [3] – Here we did not use an ensemble of photons, but rather employed the quantum Zeno effect for inferring the polarization expectation value using a genuine single photon. This was the first demonstration of protective measurement [4], similar in spirit to our proposal in [5]. The protection mechanism allows to defy the statistical character of the expectation value, which up to now was always evaluated using a large ensemble of similarly prepared particles.

I will discuss some consequences of these experiments, both theoretical (e.g. the meaning of the wavefunction) and practical (e.g. state and process tomography).

If time allows me, I will outline some of our upcoming experiments, such as those concerned with the study of entanglement and nonlocality [6,7].

References

[1] Y. Aharonov, D.Z. Albert, L. Vaidman, How the result of a measurement of a component of the spin of a spin-1/2 particle can turn out to be 100, Phys. Rev. Lett. 60, 1351 (1988).

[2] F. Piacentini, A. Avella, M.P. Levi, M. Gramegna, G. Brida, I.P. Degiovanni, E. Cohen, R. Lussana, F. Villa, A. Tosi, F. Zappa, M. Genovese, Measuring incompatible observables by exploiting sequential weak values, Phys. Rev. Lett. 117, 170402 (2016).

[3] F. Piacentini, A. Avella, E. Rebufello, R. Lussana, F. Villa, A. Tosi, M. Gramegna, G. Brida, E. Cohen, L. Vaidman, I.P. Degiovanni, M. Genovese, Determining the quantum expectation value by measuring a single Photon, forthcoming in Nat. Phys., doi:10.1038/nphys4223 (2017).

[4] Y. Aharonov, L. Vaidman, Measurement of the Schrödinger wave of a single particle, Phys. Lett. A 178, 38–42 (1993).

[5] Y. Aharonov, E. Cohen, A.C. Elitzur, Foundations and applications of weak quantum measurements, Phys. Rev. A 89, 052105 (2014).

[6] Y. Aharonov, E. Cohen, A.C. Elitzur, Can a future choice affect a past measurement’s outcome?, Ann. Phys. 355, 258-268 (2015). [7] A. Brodutch, E. Cohen, Nonlocal Measurements via Quantum Erasure, Phys. Rev. Lett. 116, 070404 (2016).

The Raman spectrum of a sample provides information about the sample's molecular content, with each individual molecule contributing its own typical "fingerprint" spectrum. However, the sensitivity of Raman Scattering as a spectroscopic method is limited by the relatively weak Raman gain of the target molecule. Coherent Anti-Stokes Raman Spectroscopy (CARS) was developed to increase the measured Raman signal by exciting the sample with two light sources: the pump and an idler with a frequency difference from the pump that matches a vibrational energy gap of the molecule being probed. However, this method introduced noise due to the non-resonant background from surrounding materials (e.g solvents) which obscures the spectrum of the target Raman molecule. Several methods used for reducing the non-resonant background, such as epi-CARS, polarization-CARS and pulse shaping techniques can surpass the non-resonant signal to some extent, but not completely reduce to the shot-noise level, resulting in low sensitivity for possible spectroscopic and imaging applications. 

The nonlinear interaction in CARS is Four-wave mixing (FWM), which converts two pump photons into signal and idler photons that obey specific relative phase relations, and experience two-mode quadrature squeezing, as previously researched in our group. We approach the problem by performing a doubly-stimulated CARS process, allowing us to exploit the unique correlation properties of the FWM light for measuring the phase shift introduced by the non-resonant FWM process, and effectively converting the standard intensity measurement into an interferometric phase measurement.  Our proposed method completely rejects the non-resonant background below the shot-noise limit and enhances the effective Raman signal. 

The theory of Compressive Sensing, a.k.a. Compressed Sampling (CS), was introduced a little more than a decade ago and it has generated a great deal of attention in a variety of areas, including applied mathematics, computer science, physics,  engineering and, in fact, almost every field that involves data sensing. The  CS theory offers a much more economical sensing framework, in terms of number of samples, compared to the traditional Shannon-Nyquist paradigm. The CS theory has found natural application for optical sensing and imaging due the large dimensionality of optical data.  By employing CS principles for optical imaging and sensing it is possible to reduce the overall acquisition time, the amount of data stored and transmitted, and the size and weight of the system. In this talk we overview the opportunities opened by compressive sensing to overcome optical sensing and imaging design limitations. Examples form our decade activity in the field will be given, including compressive 2D and 3D imaging, 4D spectral-volumetric imaging, hyperspectral and ultraspectral imaging, motion tracking and more.

Adrian Stern-short biography

Adrian Stern received his B.Sc., M. Sc. (cum laude) and PhD degrees from Ben-Gurion University of the Negev, Israel, in 1988,1997 and 2003 respectively, all in  Electrical and Computer Engineering. Currently he is a Full Professor at Electro-Optical Engineering Department at Ben-Gurion University in Israel where he serves as department head. During the years 2002-2004 he was a postdoc fellow at University of Connecticut. During 2007-2008 he served as senior research and algorithm specialist for GE Molecular Imaging, Israel. In 2014-2015, during his sabbatical leave, he was a visitor scholar and professor at Massachusetts Institute of Technology (MIT).

His current research interests include compressive imaging and optical sensing, 3D imaging, computational imaging, remote sensing,  phase-space optics.  

Dr. Stern has published almost 160 technical articles in leading peer reviewed journals and conference proceeding, more than quarter of them being invited papers.

Dr. Stern is a Fellow of SPIE, member of IEEE, OSA. He served an associate editor for Optics Express journal for six years, and served as guest Editor for IEEE/OSA Journal on Display Technology. He has edited the first book on Optical Compressive Sensing and Imaging published by CRC Press in 2016.

Looking at how structure and functionality arise in Nature, the role of emergent phenomena is evident and ubiquitous, from pattern formation in a sand pile, all the way up, in complexity, to the primate brain. In contrast, we rarely see deliberate use of these principles in human-made systems. Could we incorporate the same principles of operation and adaptability of, say, a bacterium, in a way that complements traditional engineering? 

We propose that superior technological functionalities that are difficult or impossible to achieve with linear and near-thermal-equilibrium systems can be obtained by exploiting nonlinear dynamics far from equilibrium. I will begin by briefly describing our main experimental tool, the mode-locked laser, which generates intensely powerful pulses that we use to deliver the energy that drives our systems far from equilibrium. It is telling that mode-locking, itself a self-organized, emergent phenomenon with great technological applications, has provided much of our early guidance about controlling such systems. I will then exemplify how we orchestrate the complex dynamics of physically very different systems, whereby we exert control over spatial scales that vary from the sub-micron to the atomic and vastly improve or introduce unprecedented new capabilities, addressing long-standing engineering problems in each case. 

Anderson localization is a cornerstone of our understanding of the interaction of light with disorder. But in the deep subwavelength regime, all photonic transport effects, including Anderson localization, become trivialized and effective medium theory should take over.

This talk will present work on subwavelength disordered multilayer structures – stacks of dielectric layers, where each is layer has an average thickness of lambda/40 (experimentally) or lambda/1000 (theoretically). But rather than being a weak effect, localization in this regime dominates transport completely and induces a rich regime of transport where disorder can sometimes increase transmission rather than reduce it. Furthermore, changing a single layer by 2 nm is shown to have a measurable effect on transport in visible wavelengths.

(I) Surface plasmon polaritons (SPPs) have shorter wavelengths and stronger field enhancement, confined to the dielectric-metal interface, in comparison with light and have been widely used in nano-optics, resonance sensing and imaging, including surface plasmon focusing. However, the low conversion efficiency and high propagation loss of SPPs limit its use. Controlling the propagation direction of SPPs by using nanostructures on metal surfaces is important. The manipulating of the focusing and polarization in plasmonic nanostructures is the key problems. In this lecture, we will introduce the principle and experimental of Near-field Optics, and then report the recent progress in the following aspects at Plasmonic-SNOM group, Peking University:

* Surface Plasmons in Metal

Magnetic Fano Resonance; Toroidal Dipolar Resonance; Active Control of Graphene-Based Unidirectional Surface Plasmon Launcher

* Surface Plasmons in 2D materials

Plasmonic hot electron induced structural phase transition in MoS2 monolayer; Graphene quantum dots doping of monolayer MoS2; Active Plasmonic Tuning of MoS2 Absorption and Luminescence

* Plasmonic circular polarization and Focusing surface plasmon polaritons in Archimedes’ nanostructure

(II) Nanotechnology becomes a worldwide important area. To face the challenge, China has established several key institutions around the country. One of the most important one is the National Center for Nanoscience and Technology, which is a highly interdisciplinary research institute, with the initial members of Peking University, Tsinghua University and Chinese Academy of Sciences. After 10 years of construction and running, the Center becomes the best nanotechnology research center of the country, with young scientists of physics, chemistry, biology, information, material science and medical-pharmaceuticals. We will show you the recent activities of this dynamic center.

About the Speaker:

Prof. Xing ZHU (朱星) is the leader of the Plasmonics-SNOM group of School of Physics, Peking University. He obtained Ph.D. of Natural Science at University of Saarland, Germany in 1986 and M.Sc. at University of Toronto, Canada in 1983. He has been working with scanning probe microscopy with special interests in near-field optical microscopy, the structure analysis of nanomaterials, basic theory of surface plasmon polariton and the application of Plasmonics. He was the Chair of 2nd APNFO (1999), the Chair of 10th NFO-international conference for Near-field Optics (2010). He is the council member of Chinese Physical Society, the council member of Association for Asia-Pacific Physical Societies, Member of IUPAP, Commission C2 and Expert of ISO TC229 Nanotechnologies.

Prof. Zhu is also The Deputy Direction of National Center for Nanoscience and Technology, representing Peking University.

Nimrod Kruger_­, Matej Kurtulik, Assaf Manor, Tamilarasan Sabapathy and Carmel Rotschild

Department of Mechanical Engineering, Technion − Israel Institute of Technology, Haifa 32000, Israel

The radiance of thermal emission, as described by Planck’s law, depends only on the emissivity and temperature of a body, and increases monotonically with temperature rise at any emitted wavelength. Nonthermal radiation, such as photoluminescence (PL), is a fundamental light–matter interaction that conventionally involves the absorption of an energetic photon, thermalization, and the emission of a red-shifted photon. In this quantum process, radiation is governed by the photon rate conservation and thermodynamically described by the chemical potential. Until recently, the role of rate conservation when thermal excitation is significant had not been studied in any nonthermal radiation, leaving open many questions; for example, what is the overall emission rate if a high quantum efficiency PL material is heated to a temperature where it thermally emits a rate of 50photons/sec at its bend edge, while in parallel, the PL is excited at a rate of 100photons/sec? Here we experimentally demonstrate that the answer is an overall rate of 100 blue-shifted photons/sec. In contrast to thermal emission, the PL rate is conserved if the temperature increases, while each photon is blue-shifted. A further rise in temperature leads to an abrupt transition to thermal emission where the photon rate increases sharply[1]. We also demonstrated how endothermic-PL generates orders of magnitude more energetic photons than thermal emission at similar temperatures. These findings show that PL is an ideal optical heat pump, and can harvest thermal losses in photovoltaics with theoretical maximal efficiency of 70%. Solutions of the rate equations for non-ideal quantum efficiency, experimentally measured absorption spectrum and available cavities for photon recycling predict a practical device that aims to reach 48% efficiency[2].

TBA

I will first briefly describe our work on Many-Body Photonics, that shows the role of noise and entropy in optics and lasers. An important example of this study reveals that mode-locking, which is one of the most important laser effects, is nothing but a first order phase transition. I then discuss several classical condensation phenomena in lasers, and finally describe recent experimental and theoretical results on  photon gas thermalization and lasing without an overall inversion that are unusual in lasers, and reach the possibility to observe quantum photon Bose-Einstein condensation (BEC) in standard fiber cavities at a room temperature. All these effects are done with regular erbium-doped fibers.

InAs/InP base quantum dots constitute the gain medium of the most advanced semiconductor lasers and amplifiers. Their superb properties stem from fundamental reasons and major advances in material growth and nano fabrication.

This talk highlights the dynamical properties of these lasers which have three important time scales:

• Several ps which determines the temperature insensitive modulation characteristics where record speeds have been demonstrated.
• 1-2 ps which determines the carrier relaxation dynamics into the quantum dots and the gain nonlinearities.
• Sub 2 fs which is shorter than the coherence time at room temperature and allows for quantum coherent interactions using practical optical amplifiers.

A series of experiments and various models for each of the time scales will be presented and the impact of further developments in quantum dot technologies will be discussed.

I will present the effect of thermal atomic motion on slow light using electromagnetically induced transparency (EIT). A direct consequence of the diffusion of atoms is the coherent diffusion of a stored image throughout the storage duration. The complex amplitude undergoes diffusion and therefore interference occurs. Specifically, high-order Gaussian transverse-modes are topologically stable and self-similar upon storage. During the slow propagation of the probe in the medium, the combined light-matter excitation exhibits both diffraction and diffusion-like behavior

Optical absorption of individual molecular ions and clusters can be measured by tagging with helium or other rare gas atoms. In case a resonance is hit by the laser frequency, the molecular ion is electronically excited, and the large amount of internal energy leads to boiling off helium. The signal that can be measured is the ratio in intensity between mass spectra with and without illumination, and extrapolation can be used to accurately approximate the gas phase spectrum. These experiments require the preparation of van-der-Waals bound complexes at very low temperatures. C₆₀⁺ could finally and unambiguously be confirmed as a carrier of diffuse interstellar bands by the Maier group using a trap with helium buffer gas cooling [1]. Alternatively, the cold complexes can also be produced in helium nano-droplets, where an atomically resolved phase transition could be measured in the Scheier group [2]. A record shall be given from the viewpoint of an interested observer of these experiments and of theoretical approaches and ongoing calculations for such systems. 

[1] Campbell, E. K., Holz, M., Gerlich, D. & Maier, J. P. Laboratory confirmation of C₆₀⁺ as the carrier of two diffuse interstellar bands. Nature 523, 322-323, doi:10.1038/nature14566 (2015).

[2] M. Kuhn, M. Renzler, J. Postler, S. Ralser, S. Spieler, M. Simpson, H. Linnartz, A. G. G. M. Tielens, J. Cami, A. Mauracher, Y. Wang, M. Alcamí, F. Martín, M. K. Beyer, R. Wester, A. Lindinger, P. Scheier, Nature Communication, 2016, DOI: 10.1038/ncomms13550

Matter-wave interferometry provides an excellent tool to investigate the effect of the environment on coherence. I will present several interferometry experiments done with a BEC on an atom chip and in which different effects of the environment have been investigated. First, I will discuss effects of fluctuations in the nearby environment probed with atoms trapped in a lattice very close to the surface. Then I will present the effect of gravity probed by clock interferometry, which connects to the interplay of QM and GR and “clock complementarity”. Finally, I will discuss Stern-Gerlach interferometry and describe it in the context of time irreversibility.
 

Pulsed fiber lasers have created new opportunities in commercial micromachining applications requiring superior processing speeds for small, precise features. Specifically, the growing demand for mobile device manufacturing and renewable energy related applications have paved the way for IR and Green fiber based lasers to become a key enabling technology, harnessing their typical characteristics such as high flexibility and efficiency combined with low maintenance and cost. In this talk we review the recent advances in Spectra-Physics’ V-Gen pulsed fiber laser technology offering state-of-the-art pulse energies, peak powers, and flexibility for modern micromachining applications, including touch panel displays, Li-ion battery, solar cell, semiconductor, and PCB processing.

Optical fibers support guided acoustic modes. These modes are stimulated by optical waves, and induce scattering and modulation of light. These interactions are referred to as guided acoustic waves Brillouin scattering (GAWBS) [1]. Here we describe a new application of GAWBS in fiber sensing, and extend the study of the effect to multi-core fibers (MCFs).

Optical sensors typically rely on absorption, index or scattering. These require spatial overlap between light and the test substance. Standard fibers do not provide such overlap. Hence, chemical sensors rely on photonic crystal fibers, or structural modifications. The transverse profiles of acoustic modes reach the outer cladding boundary. Acoustic oscillations are therefore affected by dissipation to the surrounding medium. We employ GAWBS in sensing of liquids outside unmodified, standard fibers [2]. Acoustic waves are stimulated and monitored from within the core. The mechanical impedance of water and ethanol is measured with 1% accuracy. The method can distinguish between aqueous solutions of different salinity [2].

MCFs are often designed to exhibit weak coupling among cores. Nevertheless, we show that acoustic modes lead to opto-mechanical inter-core cross-talk in MCFs. Analytic expressions are derived for the magnitude and spectrum of inter-core, cross-phase modulation (XPM) that is induced by GAWBS. The spectrum consists of a series of narrowband resonances. The effect is experimentally observed in a commercially-available, seven-core fiber. Agreement between analysis and measurement is excellent. On resonance, the magnitude of opto-mechanical XPM is comparable with the intra-core Kerr effect.

Last, we employ GAWBS in a new electro-opto-mechanical radio-frequency oscillator. An optical pump stimulates guided acoustic modes, which modulate the phase of a co-propagating optical probe. The probe modulation is detected and fed back to drive the pump modulation. With sufficient feedback, stable, single-mode oscillations at acoustic resonance frequencies are achieved. No electrical filtering is required.

References

[1] R. M. Shelby, M. D. Levenson, and P. W. Bayer, "Guided acoustic-wave Brillouin scattering," Phys. Rev. B 31, 5244-5252 (1985).

[2] Y. Antman, A. Clain, Y. London and A. Zadok, "Optomechanical sensing of liquids outside standard fibers using forward stimulated Brillouin scattering," Optica 3, 510-516 (2016).

In recent years there have been extensive efforts to solve hard computational problems by realizing physical systems that can simulate specific problems. Here we present a new method in which a modified degenerate cavity (MDC) is used to solve hard computational tasks. The MDC possesses a huge number of degrees of freedom (300,000 modes in our system) that can be coupled and controlled. Specifically, the MDC allows direct access to both the x-space and k-space components of the lasing mode. Placing constraints on these components can be mapped to different computational minimization problems. Due to mode competition, the laser selects the mode with minimal loss and finds an optimal solution.  Details of our experimental system will be presented, as well as recent results demonstrating the ability to use the MDC for simulating XY spin systems and finding their ground state, for phase retrieval, for imaging through scattering medium and more. 

Linear electrostatic traps are a powerful experimental tool with applications ranging from experimental studies of the molecular reaction dynamics of four-atom systems using photoelectron-photofragment coincidence (PPC) studies to massive (micron-sized) particles. Examples of applications to molecular reaction dynamics will be provided by our recent study of the dissociative photodetachment of the F¯(H₂O) anion. In concert with state-of-the-art theory, these benchmark studies are providing a foundation for a first-principles understanding of ever-more complex chemical phenomena. To illustrate applications to nanoparticles, a new nanoparticle accelerator/decelerator capable of preparing single mass- and charge-selected nanoparticles for impact studies on surfaces will be discussed.

This work was supported by the U.S. Department of Energy Office of Science, Office of Basic Energy Sciences under Award Number DE-FG03-98ER14879 and the NSF Division of Chemistry under grant CHE-1229690.

Quantum mechanics exhibits several peculiar properties, differentiating it from classical mechanics. One of the most intriguing is that variables might not have definite values. A complete quantum description provides only probabilities for obtaining various eigenvalues of a quantum variable. The eigenvalues and corresponding probabilities specify the expectation value of a physical observable, but they are known to be statistical properties of large ensembles. In contrast to this paradigm, we demonstrate a unique method allowing to measure the expectation value of a physical variable on a single particle, namely, the polarization of a single protected photon. This is the first realization of quantum protective measurements [1,2], which are based on a combination of weak measurements and the quantum Zeno effect. Before discussing these issues, I will review the notion of weak measurements [3-5] and discuss their realization by presenting our previous experiment [6], where we measured two non-commuting observables, on one and the same photon, using sequential weak measurements. I will conclude by discussing a few applications of these methods, both in metrology and in the study of foundational questions.

References
[1] Y. Aharonov, L. Vaidman, Measurement of the Schrӧdinger wave of a single particle, Phys. Lett. A 178, 38 (1993).
[2] Y. Aharonov, E. Cohen, Protective measurement, Post-selection and the Heisenberg representation, in Protective measurement and quantum reality: Towards a new understanding of quantum mechanics, Shan Gao (Ed.), Cambridge University Press (2014), arXiv: 1403.1084.
[3] Y. Aharonov, D.Z. Albert, L. Vaidman, How the result of a measurement of a component of the spin of a spin-1/2 particle can turn out to be 100, Phys. Rev. Lett. 60, 1351 (1988).
[4] Y. Aharonov, E. Cohen, A.C. Elitzur, Foundations and applications of weak quantum measurements, Phys. Rev. A 89, 052105 (2014).
[5] Y. Aharonov, E. Cohen, A.C. Elitzur, Can a future choice affect a past measurement's outcome?, Ann. Phys. 355, 258-268 (2015).
[6] F. Piacentini M.P. Levi, A. Avella, E. Cohen, R. Lussana, F. Villa, A. Tosi, F. Zappa, M. Gramegna, G. Brida, I.P. Degiovanni, M. Genovese, Measuring incompatible observables of a single photon, Phys. Rev. Lett.. 117, 170402 (2016).

The metamaterials community has been heavily excited since the publication of two articles by Pendry and Leonhardt in 2006, in which exotic devices, such as invisibility cloaks were proposed to be implemented by space transformation. Indeed, the form invariance of the Maxwell equations allow for an equivalence between a deformed geometry and a material with specific properties. Since then, several experimental studies have shown the feasibility of such transformed devices. The form invariance was also found in other physical domains and the space transformations were applied to many physcial phenomena such acoustic wave propagation, elasto-dynamic wave and surface wave propagation. We present in this work the space transformation applied to the heat equation. Throughout our study, we focus on the transformations leading to thermal invisibility cloaks and thermal concentrators. Those transformed devices are made of anisotropic heterogeneous materials which make them difficult to practically design. Therefore, we make use of the two-scale homogenization theory , allowing to approach the behavior of those devices with an alternate set of isotropic materials. We systematically try to evaluate quantitatively the performance of our approximate devices by defining an effectiveness criterion to achieve high level of mthermal metamaterials engineering. Finally, we present a model of a 50-layer carpet cloak, whose first results are to be expected.

The most convenient way to send a quantum state from one quantum system to another, remote, one is by using single photons.

So far there have been very few demonstrations of such 'photonic quantum links', and those can be categorized into three types, one of them demonstrated in our group. I will review these three approaches and present the corresponding experimental demonstrations, from other labs worldwide, and from ours.

Advances in medicine and technology are opening a new era of portable healthcare. Together with health apps, wearable/portable health monitoring systems are targeting medical diagnosis or health and wellness. The development of Wearable Health Monitoring Systems (WHMS) has been motivated mainly by increasing healthcare costs and by an aging world population. Optical techniques are widely used in clinical settings and in biomedical research to interrogate bio-molecular interactions and to evaluate tissue dynamics. Miniature integrated optical systems for sensing and imaging can be portable, enabling long-term imaging studies in living tissues.  Fluorescent dyes are frequently used to mark biological samples, and track tissues, cells and individual molecules. In the lab, fluorescence is used to understand physiology and develop new cures to common diseases. In the clinic, fluorescence is used to diagnose health conditions and to evaluate treatments. Translating fluorescence imaging to portable healthcare systems will help us take better care of ourselves.

This seminar will review fundamental properties of fluorescence, tissue absorption and scattering and show how these can be used to track vital signs and provide wellness indicators during a physical activity. We will review examples of portable imaging systems in rapid disease diagnosis, and in health monitoring.

Biography

Dr. Ofer Levi is an Associate Professor in the Institute of Biomaterials and Biomedical Engineering and the Edward S. Rogers Sr. Department of Electrical and Computer Engineering at the University of Toronto, currently on a Sabbatical leave at Stanford University. Dr. Levi received his Ph.D. in Physics from the Hebrew University of Jerusalem, Israel in 2000, and worked in 2000-2007 as a Postdoctoral Fellow and as a Research Associate at the Departments of Applied Physics and Electrical Engineering, Stanford University, CA.  He serves as an Associate Editor in Biomedical Optics Express (OSA) and is a member of OSA, IEEE-Photonics, and SPIE.  His recent research areas include biomedical imaging systems and optical bio-sensors based on semiconductor devices and nano-structures, and their application to bio-medical diagnostics, in vivo imaging, and study of bio-molecular interactions.  More details can be found at http://biophotonics.utoronto.ca/

During the last decade significant experimental efforts were devoted to developing detectors of nanosized -objects using whispering-gallery-mode resonances. The ultimate goal of these efforts is to achieve detection and determination of the size of a single protein. In this talk I will present recent developments concerning theoretical description of particle-induced modifications of whispering-gallery-modes both in strong and weak coupling regimes. Comparison of the theory with experimental data and ways to improve sensitivity of detection will be discussed.

We present multimodal wide-field optical interferometric microscopy techniques for label-free 3-D imaging of live cells during fast flow. Using cell micro-manipulation approaches, multiple cells are trapped and rapidity rotated, while acquired using optical interferometry. The interferometric projections are rapidly processed into the 3-D refractive-index profile of the cells. The potential of these new techniques is for label-free image analysis and sorting of cells, to substitute current cell sorting devices which are based on external labeling that eventually damages the cell sample. We show possible applications to in-vitro fertilization and cancer diagnosis.
 
Prof. Natan T. Shaked is an Associate Professor in the Department of Biomedical Engineering at Tel Aviv University, Israel. Between April 2011-July 2015, he was a Senior Lecturer (Assistant Professor) in the same department. Previously, Prof. Shaked was a Visiting Assistant Professor in the Department of Biomedical Engineering at Duke University, Durham, North Carolina, USA. Prof. Shaked heads the The Biomedical Optical Microscopy, Nanoscopy and Interferometry Research Group, a large experimental group performing a multidisciplinary research involving optical engineering, imaging and sensing in biological systems, optical therapy, and biophysics. Prof. Shaked raised more than 4 Million USD for research, including recent winning in the personal ERC grant (>1.9 Million Euro). He is the author of more than 50 refereed journal papers and more than 80 conference papers.

Many quantum systems share interesting features with wave propagation in disordered media, such as apparently diffusive dynamics with an underlying coherent structure. The interplay of these properties is interesting both from a fundamental standpoint and for applications.  

I will discuss one such problem: the statistical properties of an N-photon packet in a random elastically scattering medium. I will describe how information about the quantum state of the packet is encoded in the photon speckle pattern, how it can be measured, and why such measurements become exponentially sensitive with N. Finally I will discuss how state information is hidden in long-ranged correlations of the photon speckles.

The detection and characterization of paramagnetic species by electron-spin resonance (ESR) spectroscopy has numerous applications in chemistry, biology, and materials science [1]. Most ESR spectrometers rely on the inductive detection of the small microwave signals emitted by the spins during their Larmor precession into a microwave resonator in which they are embedded. Using the tools offered by circuit Quantum Electrodynamics (QED), namely high quality factor superconducting micro-resonators and Josephson parametric amplifiers that operate at the quantum limit when cooled at 20mK [2], we report an increase of the sensitivity of inductively detected ESR by 4 orders of magnitude over the state-of-the-art, enabling the detection of 1700 Bismuth donor spins in silicon with a signal-to-noise ratio of 1 in a single echo [3]. We also demonstrate that the energy relaxation time of the spins is limited by spontaneous emission of microwave photons into the measurement line via the resonator [4], which opens the way to on-demand spin initialization via the Purcell effect. Finally we report recent results demonstrating that squeezed microwave signals can be used to enhance ESR sensitivity even further [5]

[1] A. Schweiger and G. Jeschke, Principles of Pulse Electron Magnetic Resonance (Oxford University Press, 2001)

[2] X. Zhou et al., Physical Review B 89, 214517 (2014).

[3] A. Bienfait et al., Nature Nanotechnology 11, 253 (2016)
[4] A. Bienfait et al., Nature 531, 74 (2016)
[5] A. Bienfait et al., in preparation (2016)

The effect of Parametric Down Conversion (PDC) has been used widely as a source of non-classical states of electromagnetic radiation, such as entangled photons, squeezed light, single photons. The extension of quantum optics into the x-ray regime would open new possibilities for research. Despite the fact, that PDC in X-ray regime has been proposed about 45 years ago, no evidence of non-classical states of light in this regime has been reported yet. The main challenge is Compton scattering. Typically it is many orders of magnitude larger than PDC and completely outweighs the signal from PDC. Perhaps, even more serious problem is that Compton scattering limits the input flux to a level at which Compton scattering starts saturating the detectors.

I will describe an experiment demonstrating the possibility to generate collinear x-ray photon pairs with highly suppressed background. By choosing angles near 90 degrees between the detectors and the pump beam, where the pump polarization is in the scattering plane, we improve the signal-to-noise ratio by nearly three orders of magnitude. We measure about two coincidence counts per second with a bandwidth of 1.5 keV at the full width at half maximum.

Broadband energy-time entangled photon pairs are produced by pumping a non-linear crystal with a cw laser. Because of their quantum nature, they exhibit at the same time narrowband and short time features. Indeed the sum energy of both photons is equal to the well defined energy of the pump photon, whereas the correlation time between the two photons is of the order of few tens of femtoseconds. Those properties can be used for measurements beyond the capabilities of classical devices.
 
Here we make use of those features to study the temporal properties of photons through various media. The propagation of the entangled two-photon quantum states is described by a temporal wavefunction which is comparable for certain aspects to the one of coherent ultrashort laser pulses. However, because this light is in a continuous way regime, femtosecond timing can be performed without relying on ultrashort laser pulses of high intensities. As application, we show a proof of principle experiment where ultrafast optical coincidences of the photon pairs allow selecting only the ballistic photons for imaging through a scattering medium. Using techniques from the ultrafast optics, we are able to manipulate the two-photon wave function with the help of a pulse shaper and reconstruct the dispersion properties of a sample. Ultimately the precise temporal control of the two photon wavefunction can lead to the implementation of proposals for two-photon spectroscopy with entangled photons, allowing to reveal new properties of the investigated molecules.
 
Finally we present how the same shaping method of the wavefunction allows to encode high dimensional quantum information in the spectrum of the photons and to realize quantum information protocols.

In outer retinal degeneration, such as Retinitis Pigmentosa or Age related Macular Degeneration, the retinal photoreceptors degenerate while the inner retinal neurons are relatively preserved. Stimulation of these neurons by various technologies was shown to elicit visual percepts. Nevertheless, the visual acuity obtained by current retinal prosthesis is still very poor, probably due to a combination of technical and neural effects. An alternative emerging technology is the transplantation of photoreceptors differentiated from stem cells. Although this is a promising approach, the complexity of the photoreceptor differentiation process, pathology of the host retinal pigment epithelium and inadequate integration of the photoreceptors into the host retina, make this approach very challenging. In this lecture I will present our experience with both photovoltaic retinal prosthesis and with generation of photoreceptors from human embryonic stem cells, as potential technologies for restoration of sight. I will also introduce our novel head mounted DMD based projection system for natural and prosthetic visual stimulation in behaving animals.

Squeezed states of light are a major quantum resource in quantum optics. Their unique non-classical correlations (photon-number correlation and phase anti-correlation beyond the shot-noise limit) are a key to many quantum information applications, such as continuous variable quantum computing, quantum communication and key-distribution, teleportation, and sub-shot-noise interferometry.
Quadrature squeezing or squeezed light can span a full bandwidth of pair frequency modes that contribute together to the collective quadratures of the squeezed oscillation. The frequency separation between the modes of a pair can be anywhere between zero (degenerate squeezing) to an optical octave, and the number of simultaneous pairs is generally unlimited (an octave-spanning spectrum was demonstrated). In most experiments however, only the very special case of (nearly) degenerate squeezing is used, or just a single pair. While broad bandwidth is a welcomed resource in many other fields, the use of squeezed states is limited to narrow, almost DC, bandwidth. This is primarily due to the inherently limited bandwidth of optical homodyne measurement, which is the major tool to measure and manipulate squeezed states, and to the incompatibility of standard mode locking methods to parametric oscillators, which are the major tool for generating strong squeezing. 
In this talk I will present both a new homodyne measurement and a new generation scheme suitable for ultra-broadband squeezing; I will present a novel homodyne method for measuring optical bandwidth squeezing, demonstrating a measurement of more than 3dB squeezing over ~50THz bandwidth.  And I will present an intriguing new method for active mode-locking in a parametric oscillator, allowing the generation of broadband strongly squeezed light.

Trapped radioactive atoms and ions have become a standard tool of the trade

for precision studies of beyond SM physics.  decay studies, in particular,

oer the possibility of detecting deviations from standard model predictions

of the weak interaction which signal new physics. These 'precision frontier'

searches are complementary to the high energy searches performed by the

LHC and other high energy/high luminosity facilities.

I will present a general overview of magneto-optical and optical traps and

their use for weak interaction studies. I will further present both the Berkeley

²¹Na trapping experiment and the new Hebrew University ^17-25Ne trapping program, recent experimental results, and future plans.

1
 

Understanding the atomic scale motion of chemical reactions occurring on metal surfaces has become an important topic of research, one that is motivated by its technological implications for heterogeneous catalysis. The importance of heterogeneous catalysis for humankind can hardly be overestimated. Its application range from pollution abatement to food industry. Unfortunately, even today, in most cases we are lacking detailed molecular level understanding of these processes.  Studies carried out under ultra-high vacuum conditions, with clean surfaces and with molecules in well-defined internal state distributions provide a wealth of information based on which a detailed microscopic view of the process can be constructed. In my talk I will refer to recent studies of  diatomics collisions with single crystal coinage metals studied by combination of molecular beams and laser spectroscopy, exemplifying how detailed studies of vibrational energy transfer, rotational and translational inelasticity can provide detailed insights into the dynamics of gas surface encounters. I will also cover another aspect of our work aiming towards gas-phase fabrication (chemical vapor deposition and flame assisted synthesis) of model functional surfaces and expanding the studies of gas surface interactions beyond single crystals to complex model catalysts.

Optical oscillators present a powerful optimization mechanism. The inherent competition for the gain resources between possible modes of oscillation entails the prevalence of the most efficient single mode. We harness this 'ultrafast' coherent feedback to optimize an optical  field in time, and show that when an optical oscillator based on a molecular gain medium is synchronously-pumped by ultrashort pulses, a temporally coherent multimode field can develop that optimally dumps a general, dynamically-evolving vibrational wave-packet, into a single vibrational target state. Measuring the emitted field opens a new window to visualization and control of fast molecular dynamics. The realization of such a coherent oscillator with hot alkali dimers appears within experimental reach.

The ability to shape and focus optical waves to dimensions smaller than their wavelength has intrigued the scientific community both for its physical challenges and its potential applications. Resonant elements, , have provided deep-subwavelength control at long wavelength in the form of Metamaterials, while at optical frequencies light could be focused to specific points by nano-antenna and Nanofocusing elements, breaking the so-called diffraction limit. Alternatively,  achieving similar focusing dimensions by scaling the diffraction limit rather than breaking it allows flexible and dynamic control over the type and shape of the focusing without specifically patterning the medium, hence can provide super-resolution capabilities for bio-imaging, nanolithography and spectroscopy. We use the high refractive index of Silicon to scale the diffraction limit by  many-fold compression of the wavelength thereby achieving resolution at the order  of 10-s of nanometers at visible light. - Comparable to that of single-molecule microscopy techniques. Utilizing this scaled diffraction limit, we present phase-resolved near-field observations of propagating-waves bright and dark focusing below 70 nm at 671nm illumination (λ/10), and direct observation of short-wavelength Super-Oscillations in planar 2D Hybrid Silicon-plasmon waveguides.

After a two year shut down The Large Hadron Collider is finally back in business, 
and at a higher energy than ever before. First results from this year have just been published,
and next year much more data will be collected. The high energy frontier is just around the corner.
In the talk I will introduce the field of particles physics, and the experimental tools used to study it.
I will talk about the Large Hadron Collider, which has become the main device in particle physics 
to study the high energy frontier (Energies beyond 100GeV) . I will review the physics programme and goals behind it.
I will also show recent results which include possible hints for a new particle decaying to two photons (with an approximate mass of 750 GeV), which future data will support or refute.

I will end with hopes for the future.

Optical microscopy is a powerful tool, as it has been the workhorse of physical,
biological and medical research for over five centuries. Nevertheless, it is known 
that microscopy has some limitations. In this talk, I will show that two such major 
limitations can be overcome, namely improving the sensitivity and the resolution 
of standard optical microscopy, using quantum optical principles.

Conventionally, standard microscopy uses classical sources of light and simple 
cameras. By employing quantum light and quantum correlation
measurements, one can achieve sub-shot-noise imaging sensitivities and 
super-resolution beyond the diffraction limit, respectively.

Super-resolution fluorescence microscopy has revolutionized the field of cellular imaging in recent years. Methods based on sequential localization of point emitters (e.g. PALM, STORM) enable imaging and spatial tracking at ~10-40 nm resolution, using visible light. Moreover, three dimensional (3D) tracking and imaging is made possible by various techniques, prominent among them being point-spread-function (PSF) engineering. The PSF of a microscope, namely, the shape that a point source creates in the image plane, can be modified to encode the depth (z position) of the source. This is achieved by shaping the wavefront of the light emitted from the sample, using a phase mask in the pupil (Fourier) plane of the microscope.
In this talk, I will describe how our search for the optimal PSF for 3D localization, using tools from information theory, led to the development of microscopy systems with unprecedented capabilities in terms of depth of field and spectral discrimination. Such methods enable fast, precise, non-destructive localization in thick samples and in multicolor; we have applied them to super-resolution imaging, tracking biomolecules in living cells and microfluidic flow profiling. Super localization microscopy holds great promise as a uniquely powerful tool for future measurements of nano-scale dynamics in living systems.

Upon the discovery of Australopithecus afarensis remains in the 1970s and the subsequent acknowledgment of the remains’ distinct taxonomic status, the new species was hailed as situated anatomically and chronologically “halfway” between an ape (the common ancestor of the chimpanzee and Homo sapiens) and modern humans. Furthermore, the primitive appearance displayed by A. afarensis, along with its age, rendered it an ideal link in the chain leading to modern human. 
Beginning in the 1990s, the intensive activity of numerous expeditions to the Hadar region of Ethiopia (site of the earlier A. afarensis finds, including the famous Lucy) and the discovery of two complete skulls, filled many gaps in our understanding of A. afarensis cranial anatomy and role of this species in human evolution. 

Nitrogen-Vacancy (NV) color centers in diamond provide a unique nanoscale quantum spin system embedded in a solid-state structure. As such they are well suited for studies in a wide variety of fields, with emerging applications ranging from quantum information processing to magnetic field sensing and nano-MRI (Magnetic Resonance Imaging). Importantly, NVs possess unique optical transitions which allow for optical initialization and readout of their quantum spin state.

In this talk I will introduce the field of NV centers, and describe our research into understanding and controlling these systems, with the goal of enabling fundamental research and future applications.

I will present the techniques used for manipulation of the NV centers, and for enhancing their quantum coherence lifetime. Specifically, I will describe our recent work on extending the coherence time of arbitrary quantum states [1], and on spectrally characterizing the noise which limits coherence in shallow NVs [2]. I will then demonstrate how these approaches can be used for magnetic field sensing and nanoscale NMR (Nuclear Magnetic Resonance) and MRI. 

[1] D. Farfurnik et. al., PRB 92, 060301(R) (2015)

[2] Y. Romach et. al., PRL 114, 017601 (2015)

Reciprocity is a universal principle that has a profound impact on
many areas of physics.  A fundamental phenomenon in condensed-matter
physics, optical physics and acoustics, arising from reciprocity, is
the constructive interference of waves which propagate along
time-reversed paths in disordered media, leading to, for example, weak
localization and the metal-insulator transition. Previous studies have
shown that such coherent effects are suppressed when reciprocity is
broken. In my talk I will present our recent experiment, in which we
have shown that by tuning a non-reciprocal phase we can coherently
control weak localization of light, also known as coherent
backscattering, rather than simply suppress it [1]. By utilizing a
magneto-optical effect, we controlled the interference between
time-reversed paths inside a multimode fiber with strong mode mixing,
observed for the first time the optical analogue of weak
anti-localization, and realized a continuous transition from weak
localization to anti-localization. In the last part of the talk I will
show how we can utilize the subtle interplay between reciprocity and
mode mixing in multimode fibers for secure optical communication [2].

[1] Y. Bromberg, B. Redding, S. M. Popoff, and H. Cao, Control of
coherent backscattering by breaking optical reciprocity,
arXiv:1505.01507.
[2] Y. Bromberg, B. Redding, S. M. Popoff, and H. Cao, Remote key
establishment by mode mixing in multimode fibers and optical
reciprocity, arXiv:1506.07892.

Point defects in diamond are atomic-like systems embedded in a solid matrix. This combination enables the manipulation of light through light-matter interactions, as with isolated atoms, in addition to enabling spatial manipulations using photonic structures embedded into the solid matrix.  Specific examples include sources of quantum light, linear optical quantum gates, and quantum-optical memories (QOMs). In this talk I will focus on QOMs. These are key elements for the scaling-up of optical quantum information processing (OQIP), useful for both repeat-until success schemes of quantum computation, and for the synchronization of multiple photon events for the creation of large-scale quantum states of light, a required resource for OQIP. I’ll present our work towards the use of an ensemble of point defects in diamond for the controlled storage of quantum light. Based on previous work with atomic ensembles, I’ll explain the principles of such QOMs, and the adaptations needed for their implementation with two types of diamond defects. I’ll then present preliminary experimental results towards this goal.

We consider possible applications of temporal superoscillatory optical signals. First we discuss the delivery of a super-oscillatory optical signal through a medium with an absorbing resonance at the super-oscillation frequency. While a regular signal oscillating at the absorption resonance frequency would be completely absorbed after a few absorption lengths, it is found that the superoscillation undergoes quasi-periodic revivals over optically thick distances. In the second part of the talk we present experimental results where the use of a superoscillating optical beat breaks the optical temporal   Fourier resolution limit by an unprecedented 75%. Such superoscillatory beats can substantially increase the temporal resolution of light-driven measurement and control processes. 

The peculiarities of the Faraday effect (rotation of the plane of polarization of laser radiation in a magnetic field) are studied for the first time in the atomic vapors of the Cs and the Rb D1 lines using the nano- cells with the varying thickness L in the range of 20−900 nm. It is demonstrated that for the range of 100< L< 900 nm the Faraday rotation (FR) signal has a maximum for the highlighted thicknesses L= λ/2 = 448 nm (for the Cs) and 398 nm (for the Rb). Such type of peculiarities are absent for the common cells of centimeter-length. For the thickness L<100 nm the spectra of the FR demonstrate frequency “red shift” which gives evidence of the van der Waals (VW) effect. For the Rb atoms and L=60 nm (this is a record low L for FR observation) a giant frequency “red shift” of “-100 MHz” for the peak of the spectrum and of “- 400 MHz” for the low-frequencies-wing has been observed. For the atomic transitions VW coefficients C3 which characterize the atom-dielectric surface interaction were measured. The influence of the “recoil effect” which induces an additional “red shift” has been observed. 

  Over the past 20 years bright sources of entangled photons have led to a renaissance in quantum optical interferometry. These photon sources have been used to test the foundations of quantum mechanics and implement some of the spooky ideas associated with quantum entanglement such as quantum teleportation, quantum cryptography, quantum lithography, quantum computing logic gates, and sub-shot-noise optical interferometers. I will discuss some of these advances and the unification of optical quantum imaging, metrology, and information processing.

In order to see single photoreceptor cells in the retina, we used hardware and software tools, getting close to the resolution limit, a tenfold improvement. Transparent layers which come in front of the photoreceptors are barely seen by direct imaging, but they play a major role in improving acuity. Radial cells of higher refractive index channel some colours directly into the corresponding photoreceptors to improve their responsivity. Other colours are scattered around, and serve for night vision. Finally, simulations and experiments explained the reason why the retina is inverted, with the photoreceptors behind the neural layers. 

Human vision is based on a molecule, the retinal chromphore, which acts as an optical switch - following the absorption of a photon it undergoes an isomerization. This photoisomerization has remarkable properties - it is highly efficient, specific and fast. In order to understand this mechanism and photoisomerizations in general, we need a tool which allows us to 'see' the shape of an isolated molecule, and observe changes to the shape. These kinds of measurements have recently become possible thanks to developments in the field of ion mobility spectroscopy. In this talk I will survery the technique and present our recent study in which we measured the barrier energy for isomerization of the retinal chromphore. 

“Direct Measurement of the Isomerization Barrier of the Isolated Retinal Chromophore”, J. Dilger, L. Musbat, M. Sheves, A. B. Bochenkova, D. E. Clemmer, Y. Toker, Ang Chemie Int. Ed. 127 (2015), 4830-4834. 

In 1969 Mollow predicted that when a two-level quantum system is strongly pumped at resonance, it reemits light not only at its resonance frequency but also at two satellite frequencies. This result of quantum optics theory has been tested in many solid-state systems that can be described as two-level systems. We show that three peaks appear also when a two-dimensional electron gas confined in a quantum well is continuously pumped between two conduction subbands. Describing the resonance fluorescence with a many-body theory, we could go beyond the usual independent-dipole approximation. Remarkably, coherence in the electron gas can lead to a modified fluorescence spectrum. Moreover, with asymmetric quantum wells it is possible to engineer otherwise forbidden transitions, leading to a new tunable emission line, in the terahertz range.

BR Mollow, Phys Rev 188, 1969 (1969).
NS, CC Phillips and S De Liberato, Phys Rev B 89, 235309 (2014).

One of the most fundamental nonlinear optical effects is the change of the refractive index of the material induced by light propagating in it. This effect is used in countless applications, most prominently, in modulations of semiconductor-based electro-optic components. These modulations are most frequently based on changing the free charge-carrier density. In this case, the modulation speed is limited by the natural pico-second to nano-second carrier recombination times. However, femto-second modulation times are required for many technological applications as well as for the study of various fundamental physics problems. 
Conventional approaches for shortening the carrier lifetime rely on material-science-based modifications of the material platform. In this talk I will introduce a different approach, based on novel ideas from wave physics, and on an aspect of the nonlinear response of free-carrier which was so far ignored – carrier diffusion, or the non-local nature of the free-carrier nonlinearity. We show that this effect becomes dominant when the free-carrier distribution has nano-scale features, e.g., in the case of transient Bragg gratings. 
Based on this phenomenon, I will show how we can easily achieve sub-picosecond modulation times in semiconductors and metals. I will review the complex analysis and numerics associated with this unusual regime of pulsed wave interactions and give a glimpse into the non-equilibrium dynamics of the hot charge-carriers. Finally, I will demonstrate several novel applications such as time-reversal and short pulse generation. 

The generic “billiard problem” is a well-known paradigm of nonlinear mathematical physics, which connects to deep issues in quantum and wave physics all the way to quantum chaos. It can be implemented in mechanics, optics or electromagnetism, either in classical or quantum mechanics, depending on experimental configurations and on the billiard length-scale. The elusive borders between wave and geometric optics on the one hand, and between quantum and classical mechanics on the other, exhibit deep analogies, which can be both addressed in actual billiard-like physical systems. We will show the relevance in this context of micro-billiard shaped lasers (1-4), thanks to new experimental and technological advances in the realm of polymer based photonics at micron and submicron scales. In such configurations, confinement of light in resonators can be considered by analogy with that of a quantum particle in a well (the 2-D quantum or wave billiard). Spatially distributed modes can be connected to classical orbits within the frame of semi-classical physics approximations, by use of the celebrated “trace theorem”, herein generalized to open and chaotic cavities. A beneficial feature of dielectric cavities, in contrast with their more investigated metallised contour counterparts, is the ability for the electromagnetic wave to spread-out of the cavity by refraction, diffraction, evanescent tunnelling or a combination of these, allowing to simplify the otherwise hidden physics and eventually lending itself to sensor applications. However, such “open cavities” are more challenging from a theoretical and modelling point of view, giving raise to non-Hermitian operators and imaginary eigenvalues accounting for a finite modal excitation life-time in lossy cavities. Analytical solutions such as available for the metallized 2-D rectangle are not valid for the equivalent open structures which demand to resort either to full-fledged solutions of the Maxwell-Helmholtz equations with continuity conditions on the contour, or to application of semi-classical orbit methods. We will show consistence between those two avenues and experimental findings. Particular attention will be paid to recent advances: systematic investigations of triangular cavities (5) and extension to 3-D micro-billiards (6). The role of contour singularities will be evidenced and the related diffractive orbits pin-pointed. The technological precision required for such studies is reached by advanced e-beam patterning methods applied to dye-doped polymer structures, down to the required nano-scale level of precision.
Our investigations illustrate an approach whereby, contrary to the more academic pathway from upstream mathematical predictions down to experimental applications, experimental findings may help provide guidelines towards otherwise elusive mathematical problems, such as the diffraction of light by a dielectric prism that the lasing property allows to illuminate from its inside. 
This is being performed at LPQM/ENS Cachan, together with Clément Lafargue (Ph.D. student), Stefan Bittner (postdoctoral) and Mélanie Lebental (assistant professor) within our “microlaser and nonlinear dynamics” research group.

 (1) Directional emission of stadium shaped micro-lasers, M.Lebental, J.S.Lauret, J.Zyss, C.Schmidt, E.Bogomolny, Phys. Rev. A 75, 033806 (2007)
 (2) Inferring periodic orbits from spectra of shaped micro-lasers, M.Lebental, N.Djellali, C.Arnaud, 
J.-S.Lauret, J.Zyss, R.Dubertrand, C.Schmit, E.Bougomolny, , Phys Rev. A, 76 023830 (2007).
 (3) Organic Micro-Lasers: A New Avenue onto Wave Chaos Physics, M.Lebental, E.Bogomolny and J.Zyss, Chapter 6, pp. 317-353 in “Practical Applications of Microresonnators in Optics and Photonics”, Andrey Matsko editor,(CRC Press, Boca Raton, 2009)
(4) Trace formula for dielectric cavities. II. Regular, pseudointegrable, and chaotic examples E.Bogomolny, N.Djellali, R.Dubertrand, I.Gozhyk, M.Lebental, C.Schmit, C.Ulysse and J.Zyss, Phys.Rev. E 83, 036208 (2011)
(5) Localized lasing modes of triangular organic microlasers, C. Lafargue, M. Lebental, A. Grigis, C. Ulysse, I. Gozhyk, N. Djellali, 
J. Zyss and S. Bittner, Phys.Rev.E 90, 052922 (2014)
(6) Three-dimensional organic microlasers with low lasing thresholds fabricated by multiphoton and UV lithography
Vincent W. Chen, Nina Sobeshchuk, Clément Lafargue, Eric S. Mansfield, Jeannie Yom, Lucas R. Johnstone, Joel M. Hales, Stefan Bittner, Séverin Charpignon, David Ulbricht, Joseph Lautru, Igor Denisyuk, Joseph Zyss, Joseph W.Perry and Melanie Lebental
Optics Express 22 (10), 12316-12326 (2014)

Aklali vapor has long been a substantial tool in studying the atom-photon interactions in a well controlled environment, as well as the atom-atom interactions. The random spin-exchange collisions in warm alkali vapor are known to cause rapid decoherence, and act to equilibriate the spin state of the atoms. In this work we demonstrate experimentally that in contrast to the general concept of the collisions as a source of decoherence, a coherent coupling of one alkali specie (potassium) to another specie (rubidium) can be mediated by these random collisions.
Consequently, the potassium inherits the magnetic properties of the rubidium,
including its liftime (T1), coherence-time (T2), gyromagnetic ratio, and SERF magnetic field threshold. We further show that this coupling can be completely controlled by varing the strength of the magnetic field. Finally, we explain these phenomena analytically by modes-hybridization of the two species via spin-exchange collisions.

The manufacturing of nanometric scale semiconductor structures in the chip industry requires extremely tight non-demolition process control. Modern transistors are about 10 nm wide - orders of magnitude smaller than the resolution limits of optical microscopes. Still, it is possible to tell whether a transistor is an angstrom too wide or too narrow using optical metrology tools. I will introduce Nova’s technology and describe the methods by which we can very precisely follow the chip fabrication process in real time.

Quantum decoherence is usually an unwanted effect, and efforts are made to minimize it. This is because it acts as an information noise that encumbers the realization of many quantum information schemes and protocols. It appears that creating such noise with well defined properties is also a hard task. We will present a way in which we apply such noise in a controllable way on quantum bits (qubits) encoded in the polarization of single photons. The implementation and the characterization of principal unital quantum channels such as dephasing and isotropic channels using birefringent crystals will be discussed. 

Applying the noisy channels to photon pairs, we were able to explore the quantum-to-classical transition of initial quantum states. We will elaborate on the ability of the photon pairs to exhibit entanglement or other quantum correlations such as nonlocality and contextuality in the presence of different types and levels of noise. Specifically, we will show that the generated initial states can exhibit quantum contextuality by violating the Klyachko-Can-Binicioğlu-Shumovsky (KCBS) inequality, and that the predicted hierarchy between quantum nonlocality and KCBS contextuality (i.e., KCBS contextuality implies nonlocality) is valid for states that experienced different types of decohering unital channels.

Exoplanetary transits are the periodic dimming of stars caused by the crossing of a black and opaque disk (the planet) in front of them". In this talk I will review many of the ways in which the former sentence is wrong: planets are neither opaque, nor non-luminous or disk-like, and transits may be neither color-neutral, constant in depth, duration or even have constant period. I will briefly describe how each and every one of these variations can tell us something about the planet and/or its system.I will then focus on the non-periodicity of planetary transits known as transit timing variations (TTVs). I will discuss its observational and dynamical origins, and show examples of the challenges and opportunities brought about by this new and exciting field of exoplanet studies, including new analytical tools and ground-based observational opportunities

Asymmetric molecules look and react differently when viewed from one side or the other.
This difference influences the electronic structure of the valence electrons,
thereby giving stereo sensitivity to chemistry and biology. I will show how the
attosecond and re-collision science provides a detailed and sensitive probe
of electronic asymmetry. I will demonstrate how a high-density gas can be oriented, report the first experimental observation of even and odd harmonics generated from oriented molecular samples and discuss the physical mechanism leading to orientation. The harmonic spectrum encodes three manifestations of asymmetry; an amplitude and phase asymmetry in electron tunneling; an asymmetry in the phase that the electron wave packet accumulates relative to the ion between the moment of ionization and recombination; and an asymmetry in the amplitude and phase of the transition moment.  The sensitivity of the high harmonic spectrum to subtle phase differences will drive major advances in the theory of high harmonic generation and give us detailed insight into the molecule itself

Distributed Acoustic Sensing (DAS) has been attracting considerable amount of attention in recent years for various applications including intrusion detection, railroad monitoring, pipeline protection, seismic profiling, oil and gas well monitoring, underwater acoustic sensing and more. In many such applications sub-meter spatial resolution is necessary in order to allow accurate sampling of the acoustic phase front at high frequencies. For instance, acoustic waves in water propagate at a typical velocity of ~1.5 km⁄s  , which means a wavelength of ~15cm for a frequency of 10KHz. All current implementations of DAS are based on fiber-optic reflectometry. Most DAS methods obtain the position information from the time delay of the backscattered signal. The spatial resolution in these methods is determined by the duration of the interrogating pulse. Hence, as in Optical Time-Domain Reflectometry (OTDR), there is a fundamental inherent tradeoff between the spatial resolution and the Signal to Noise Ratio (SNR). Typical OTDR based DAS systems have spatial resolution of ~10m or more. In contrast our approach is based on Optical Frequency Domain Reflectometry (OFDR). OFDR is a well-established method for measuring the reflection profile of an optical fiber. The method is based on transmitting, into the fiber, light whose instantaneous frequency varies linearly with time. The backscattered light from the fiber is then mixed with a reference and detected. The detector output (the beat signal) is Fourier-transformed to yield spatial information. In contrast with time domain reflectometry, OFDR enables excellent spatial resolution alongside with high SNR. In the talk I will describe the various approaches for implementing DAS and some of our work on the development and characterization of OFDR based DAS.

Freeform optical design concerns optical elements that have no apriori symmetry. I shall present a few concepts  in this area, both in imaging and nonimaging optics. I shall illustrate these concepts via several examples, including novel measurement devices, beam shaping lenses and adjustable spectacles.

The nonlinear interactions between X-rays and optical radiation were first described about forty years ago by Freund & Levine [1] and by Eisenberger & McCall [2]. These studies addressed several nonlinear processes including parametric-down conversion of X-rays into the optical region, sum and difference-frequency generation of X-rays and optical pulses. However, until very recently there was no experimental evidence for any of those effects due to the absence of sufficiently bright X-ray sources. Recently, the new X-ray free-electron lasers have enabled the observation of X-ray and optical frequency mixing [3]. 
A new development in X-ray free-electron lasers has opened the possibility to generate two X-ray ultrashort pulses at different central wavelengths, with controllable delay between them. Motivated by this development, we studied the generation of short optical pulses from the X-ray pulses via the process of difference-frequency generation. We found that since the X-ray damage threshold is much higher than the optical damage threshold, the efficiency of difference-frequency generation from two X-ray pulses is orders of magnitude higher than the efficiency of frequency mixing between X-rays and optical intense short-pulses. Moreover, we show that the effect can be used for microscopic studies of chemical bonds and as a probe for light-matter interactions on the atomic scale and with temporal resolution on the order of 10 fs with the current performances of X-ray free-electron lasers. 
References and links
1.    I. Freund and B. F. Levine, “Optically modulated X-ray diffraction,” Phys. Rev. Lett. 25(18), 1241-1245 (1970).
2.    P. M. Eisenberger and S. L. McCall. “Mixing of X-ray and optical photons,” Phys. Rev. A 3(3), 1145-1151 (1971).
3.    T. E. Glover, D. M. Fritz, M. Cammarata, T. K. Allison, Sinisa Coh, J. M. Feldkamp, H. Lemke, D. Zhu, Y. Feng, R. N. Coffee, M. Fuchs, S. Ghimire, J. Chen, S. Shwartz, D. A. Reis, S. E. Harris and J. B. Hastings, “X-ray and optical wave mixing,” Nature 488(7413), 603-608  (2012).

During the last decade significant advances in controlling nano objects and polymer/DNA clusters with optical traps have been demonstrated along with the ability to create various phase changes induced by photon pressure. Here we present a novel method were colloidal particles are created when an optical trap is introduced while an emulsion polymerization is taking place. Nucleation seeds, oligomers and micelles are attracted to the trap and (under certain parameters) can coalesce or partly fuse before final polymerization, creating spherical or rod like colloids. Furthermore, we can create organic/inorganic colloidal hybrids if inorganic nanoparticles (NP) are introduced to the organic system undergoing polymerization while optical traps are present. Via a physical absorption process these nanoparticles are incorporated in the growing colloidal particle.

These methods hold great promise for creating on demand tailor made colloidal systems where size, shape and composition could be precisely controlled. The versatility and ease of making various changes to the end product without the need for chemical modifications (as the optical trap influences any material with higher polarizability than the surrounding medium) makes this approach appealing for testing model systems.

Realizing and engineering optical non-linearity at the level of single
photons is a goal of scientific and technological significance. We obtain
strong interactions between propagating photons by coherently coupling them
to Rydberg atoms in a cold gas. While slowly traversing the medium, the
"Rydberg polaritons” interact via the Van-der-Waals force, owing to their
large electric dipole-moment. We are able to vary the dynamics of the
two-photon wavefunction from dispersive (Schrodinger-like) to dissipative
(diffusion-like) and observe strong bunching, anti-bunching, and a
conditional phase-shifts of 1 radian for two individual photons.

Quantum squeezing - the reduction of noise fluctuations below the shot-noise limit in one quadrature of the light at the expense of amplified noise in the other quadrature - offers great opportunities for precision measurement and  quantum information. Current detection methods for quantum squeezing are unfortunately limited by detectors bandwidth, allowing experimental access only to narrowband squeezing. I will describe our efforts to develop broadband detection schemes for quantum squeezing and to exploit it in quantum measurement. I will specifically describe how classical methods from the RF domain can inspire quantum detection using the optical nonlinearity as the physical correlation detector 

Answering questions of health and medicine frequently necessitates the collection of data from large cohorts during real-world interactions. This is costly and, in many cases, extremely challenging due to the nature of these interactions and the difficulty in getting people to report about them. Work in recent years has shown that data generated by people as they browse the Web, including queries submitted to Internet search engines, social media postings, and even merely browsing histories can be used to learn about peoples’ activities in the virtual as well as the physical worlds. Therefore, these data could potentially serve as a cheap alternative for real-world data.
In this talk I will show that specific types of Internet data are less influenced by reporting biases, and are thus a low-cost alternative for extracting medical information from very large populations. I will discuss areas where Internet data are especially advantageous for addressing questions of health and medicine, and how these data can be coupled with other information in a privacy-preserving manner to improve the range of questions we can answer. I will illustrate with several recent examples such as post-market drug surveillance, discovery of a link between medial portrayal of underweight models and the development of anorexia, and the prediction of mood disorder events.

The signal to noise ratio of quantum sensing protocols scales with the square root of the coherence time. Thus increasing this time is a key goal in the field.  By utilising quantum error correction, I will present a novel way of prolonging such coherence times beyond the fundamental limits of current techniques. I will present an  implementable sensing protocol that incorporates error correction, and discuss the characteristics of these protocols in different noise and measurement scenarios. The use of entangled vs. unentangled states, and error correction's reach of the Heisenberg limit will be discussed

Observing and Evading Quantum Backaction in an Interferometer 
N. S. Kampel, T. P. Purdy, P.-L. Yu, R. W. Peterson, and C. A. Regal

The pursuit to eliminate classical noise sources in an interferometer has a long history. Only recently have experimental conditions matured enough to enable measuring quantum backaction in the continuous displacement detection of a solid mechanical resonator. Moreover reaching the regime in which mechanical vacuum fluctuations dominate opens the door to variety of experiments, from ultra-high position and force sensitivity to producing mechanical quantum states.
We use a macroscopic silicon nitride membrane resonator in a high-finesse optical cavity to measure the quantum backaction put forth by a light probe. Here I present initial results of two experiments. In the first we avoid the quantum backaction, and in the second we measure evidence of the resonator being in the quantum mechanical ground state.

The resolution of conventional optical lenses is limited by the wavelength. Materials with negative refractive index have been shown to enable the generation of an enhanced resolution image where both propagating and non-propagating waves are employed. We analyze such a Veselago lens by exploiting some exact one dimensional integral expressions for the quasi-static electric potential of a point charge in that system. Those were recently obtained by expanding that potential in the quasi-static eigenfunctions of a three-flat-slabs composite structure. Numerical evaluations of those integrals, using realistic values for physical parameters like the electric permittivities of the constituent slabs and their thicknesses, reveal some surprising effects: E.g., the maximum concentration of the electric field occurs not at the geometric optics foci but at the interfaces between the negative permittivity slab and the positive permittivity slabs. The analysis provides simple computational guides for designing such structures in order to achieve enhanced resolution of an optical image.

The implementation of recently developed technique based on narrowband laser diodes, strong permanent magnets and micro-and nano- thin optical cells make studies of the atomic transitions behavior in an external strong magnetic field  simple and robust [1,2].

            Particularly, the magnetic field-induced giant modification of probabilities for seven components of 6S_1/2, Fg = 3 → 6P_3/2, Fe = 5 atomic transition of the Cs D₂ line, forbidden by selection rules (at zero magnetic field), is observed experimentally for the first time. The applied theoretical model describes very well the experimental curves [3].

            So called Hyperfine Paschen Back (HPB) regime has been demonstrated for the Potassium atoms (for the first time) in the presence of strong magnetic field. Important and striking peculiarities of HPB regime for Potassium atoms observed with the help micro-and nano- thin optical cells will be presented.

References

[1] A.Sargsyan,A.Tonoyan,R.Mirzoyan,D.Sarkisyan, A.Wojciechowski,W.Gawlik, Optics Letters, 39, 2270 (2014).

[2] A. Sargsyan, G. Hakhumyan, R. Mirzoyan, D.Sarkisyan, JETP Letters 98, 441(2013).

[3] A Sargsyan, A Tonoyan, G Hakhumyan, A Papoyan, E Mariotti, D. Sarkisyan, Laser Physics Letters, 11  , 055701 (2014).

2D photon echo studies on light harvesting systems
have generated considerable interest and controversy regarding 
the possible role of quantum coherence effects in biological systems.
As we have previously shown, such studies rely on the response of
molecular systems to pulsed laser excitation, which is 
dramatically different than the response to natural incoherent
light. Significantly, the latter produces mixed stationary states,
devoid of time dependent coherences. If this would be ``the whole 
story", then the observed coherences are essentially irrelevant.

We will describe the origin of the above result and then discuss recent
developments in this area, including (a) the importance of various 
decoherence time scales for reaching stationary states in natural incoherent
light, (b) the role of doorway states in the molecular response, and (c) the
significance of long lived coherences associated with Agarwal-Fano resonances.
Examples will be chosen from basic three level V-systems,
dynamics in large molecules, and Rydberg atoms
interacting with the cosmic microwave background. The significance of the
results for natural light harvesting systems will be emphasized.

A quantum polarized light microscope using entangled NOON states with N = 2 and N = 3 is
shown to provide phase super-sensitivity beyond the standard quantum limit. We constructed such
a microscope and imaged birefringent objects at a very low light level of 50 photons per pixel, where
shot-noise seriously hampers classical imaging. The NOON light source is formed by combining a
coherent state with parametric down converted light. We were able to show improved phase images
with sensitivity close to the Heisenberg limit.

   In high frequency strong laser fields the oscillating electrons in an atom behave like they are moving not in a field induced by a positive point charge of the nucleus but in a field which is smeared along the  polarization direction of the light and it is peaked at +/- of the quiver length (defined as the ratio between the maximum field amplitude and the square of the laser frequency multiplied by the mass of the electron). 
We show that for many electron atoms (such as sulfur and oxygen) the ground state of the laser dressed atom has a long lifetime and can be degenerated. Hence, a strong linear Stark effect rather than the usual quadratic one is obtained. 
We show that also a new type of chemical reactions is induced by the high frequency strong laser fields. For example, strong chemical bond (dissociation energy is more than 12 eV) is generated between two helium atoms with a bond length of 2 Angstroms. Similarly a strong chemical bond is created between sulfur and helium atoms which is somehow similar in its nature to the chemical bond in OH radicals.

  P.  Balanarayan and N. Moiseyev, "Strong chemical bond of stable He2 in strong linearly polarized laser fields", Phys. Rev. A 85, 032516 (2012).
P.  Balanarayan and N. Moiseyev, "Chemistry in high-frequency strong laser fields: the story of HeS molecule", Mol. Phys. 111, 1814 (2013).
  P.  Balanarayan and N. Moiseyev, "Linear Stark effect for sulfur atom in strong high frequency laser fields", Phys. Rev. Lett. 110, 253001 (2013).

The first model of stationary superradiance, the superradiant laser, was suggested by Haake et al. [1]. Since then, several theoretical papers discussing this scheme, as well as some other models, have been published [2]. The key mechanism responsible for stationary superradiance in such lasers is the collective nonlinear spontaneous decay of one of the atomic states that is imposed by an additional, ”passive” resonator. As we have shown recently [3], the super/subradiant lasing can be obtained by replacing the passive resonator by a second coherent pumping laser field, so that no initial atomic cooperativity is required. In this talk the results of semiclassical treatment of a three-level ladder model of super/subradiant laser will be discussed in details.
[1] F. Haake, M. I. Kolobov, C. Fabre, E. Giacobino, and S. Reynaud, Phys. Rev. Lett. 71, 995 (1993).
[2] F. Haake et al, Phys. Rev. A 54, 1625 (1996); I. E. Mazets and G. Kurizki, J. Phys. B 40,
F105 (2007); C. Wiele et al, ibid, 60, 4986 (1999); D. Yu and J. Chen, ibid, 81, 053809 (2010).
[3] G.A. Koganov and R. Shuker, Opt. Lett. 36, 2779 (2011).

We performed in-situ sensing of volatile droplet and spray liquid mass using plate-like micro-resonator plates with low compressive stress, where robust and reusable operation over harsh conditions and multiple cycles was proven. A home-built electro-optical motion sensing system in ambient conditions was been used. The bimorph effects on the resonant frequency of altered mass loading, elasticity and strain have been compared, and the latter were found to be negligible in the presence of non-viscous liquids deposited on top of the devices. In resonant mode, the loaded mass is estimated from measured resonant frequency shifts and interpreted from simple (uniformly deposited film) model.

A minimum sub-ng detectable mass has been estimated, suggesting the potential for fast and reusable sensing capabilities of volatile liquids under harsh operation conditions.
We also describe very efficient parametric actuation in electro-statically excited single-layer microresonators, which can be employed in future integrated surface material sensors (for both liquid and vapor environments)
 
Ref:s     [1] submitted, IEEE Journal of Selected Topics in Quantum Electronics special issue on optically based sensors (2014)
            [2] J. Appl. Phys. 113, 163508 (2013)
 

The limitations of high power single mode fiber lasers such as stimulated Raman scattering, thermal lensing and modal instabilites are presented. In order to scale-up the power from high beam quality fiber laser sources, incoherent beam combinging is being employed, yielding a kWatt scale high brightness source .

We demonstrate wide-angle, broadband and efficient reflection holography by utilizing coupled dipole-patch nano-antenna cells to impose an arbitrary phase profile on of the reflected light. High fidelity images were projected at angles of 450 and 200 with respect to the impinging light with efficiencies ranging between 40%-50% over an optical bandwidth exceeding 180nm. Excellent agreement with the theoretical predictions was found at a wide spectral range.  The demonstration of such reflectarrays opens new avenues towards expanding the limits of large angle holography.

A setup for preparing the Bose–Einstein condensate of Rubidium atoms is described. The condensate consists of 10⁵–10^{6 87}Rb atoms in the hyperfine state Fg = 2 of the ground electronic state. Three key indications of condensation, a sharp increase in the phase space density of atoms, the threshold emergence of two fractions in the cloud, and anisotropic expansion of the condensate, have been observed.

The future experiments with the Rubidium BEC are discussed. The plans are to create very cold samples using BEC and to study the properties of BEC at variable interatomic interactions.

High harmonic generation is an extreme nonlinear process in which infrared or visible radiation is frequency up-converted into the extreme ultraviolet and x-ray spectral regions. As a parametric process, high harmonic generation should conserve the radiation energy, momentum and angular momentum. Indeed, conservation of energy, momentum and orbital angular momentum have been demonstrated. On the other hand, conservation of spin (polarization) angular momentum has thus far never been studied, neither experimentally nor theoretically.
 
I will present the first study on the role of spin angular momentum in extreme nonlinear optics. In our experiment, we generate high harmonics of bi-chromatic elliptically-polarized pump beams that interact with isotropic media. While observing that the selection rules qualitatively correspond to spin conservation, we unequivocally find that the process of converting pump photons into a single high-energy photon does not conserve angular momentum. In one regime, we find that this major discrepancy can be explained if the harmonic photons are emitted in pairs.

TBA

Understanding the mechanisms of chemical reactions is a central goal of chemistry. Most photochemical reactions occur in excited electronic states and are governed by the excited potential energy surface. Except for very small molecules it is extremely challenging to know these potentials with any reasonable accuracy. 
We have recently shown that one can reconstruct the complete excited-state wavefunction (WF) of a reacting molecule [1,2]. Generally, WF reconstruction methods require a priori knowledge of the excited potential [3,4]. The WF reconstruction methodology we propose uses no a priori information on any excited state, but only of the ground state. We express the excited-state WF in the basis of the (assumed known) ground vibrational eigenstates. The superposition coefficients can then be extracted by inversion of a multi-dimensional CARS signal. The method applies to polyatomics, and to dissociative as well as bound excited potentials. Finally, the unknown excited potential can be recovered from the excited WF.

[1] D. Avisar and D.J. Tannor, PRL, 106, 170405, (2011).

[2] D. Avisar and D.J. Tannor, JCP, 136, 214107, (2012).

[3] M. Shapiro et al, PCCP, 12, 15760, (2010).

[4] J.A. Cina, Annu. Rev. Phys. Chem., 59, 319, (2008).

The separation of electronic and vibrational times scales opens the possibility that electronic matter in a highly excited incoherent state coexist for a short time with cold vibrations. During this short time, of a picosecond or less, the hot electrons can emit thermal electrons with extremely high temperatures from clusters and fullerenes.

Experiments on fullerenes and endoheral fullerenes with femtosecond laser pulses at deep sub-threshold photon energies will be presented. In the experiments electron energy distributions and ionic photo-fragmentation have been measured and analyzed in terms of this hot electron model.

Dipolar interactions lay at the basis of a variety of phenomena in physics and chemistry, ranging from fundamental quantum vacuum forces and energy transfer all the way to emerging quantum technologies.  This work concerns the important possibility to drastically modify these dipole-dipole interactions, thus potentially affecting much of the above phenomena:  Since the interactions between dipoles are mediated by (virtual) photon modes, they can be enhanced by considering dipoles embedded in geometries that confine these modes. In this context, I will present our results on the possibilities for giant van der Waals and Casimir interactions via transmission lines, long-range deterministic entanglement and non-additive many-body physics with laser-induced interactions.

Neutron scattering is a powerful suite of scientific tools for determining the structure and dynamics of matter. The technique is widely used in physics, materials science, biology, and engineering. National neutron scattering facilities are billion-dollar 
installations, serving hundreds of scientists per year. While modern light optical 
instruments use a variety of focusing devices (such as lenses and mirrors) and techniques (structural illumination, phase-contrast microscopy, etc), neutron instruments remain in the age of pinhole cameras. Were powerful optical tools available for neutron scattering, they might bring significant, even transformative, improvements to rate-limited neutron methods and enable new science. The MIT/NASA collaboration have recently pioneered the use of axisymmetric focusing mirrors, which have the potential of transforming neutron imaging and scattering instruments from pinhole cameras into microscopes. I will show how such reflecting lens could help increasing the resolution of neutron imaging and scattering instruments. (For a more extended introduction, see: http://www.materials360online.com/newsDetails/42202)

I will present our progress towards the demonstration of a 1-atom based single-photon switch, utilizing cavity-QED with toroidal micro-resonators.
Practical single-photon switching, namely controlling the direction of one single-photon pulse with a control field that is another single-photon pulse, has not been achieved experimentally to date.
This device will also function as a 1-qbit quantum memory, enabling a deterministic quantum state transfer between a single photon and an atom, with no need for any control field.

Prof.  Carmon has conducted a series of beautiful groundbreaking experiments on optomechanical effects in microshpere resonators.  His work includes the demonstration of interesting effects such as spontaneous Brillouin cooling, Brillouin cavity optomechanics with microfluidic devices and many more. He is a great speaker who uses basic intuition to describe his results. Note the attached picture. 

In 2005 we were reporting on the centrifugal radiation pressure of light as a new mechanism for actuating mechanical vibrations. Today I will describe our recent results in cooling via light-sound interaction and optical excitation of vibration at >10 GHz rates.

In 2005 we were reporting on the centrifugal radiation pressure of light as a new mechanism for actuating mechanical vibrations. Today I will describe our recent results in cooling via light-sound interaction and optical excitation of vibration at >10 GHz rates

In the early days of laser cooling of atomic gases, unexpectedly low temperatures were discovered in different laboratories across the world. A new cooling mechanism, called Sisyphus cooling, proposed by J. Dalibard and C. Cohen-Tannoudji, explained these findings and led later to Nobel Prize in physics awarded to C. Cohen-Tannoudji in 1997. Unfortunately, this elegant mechanism doesn’t apply for all atomic species used in ultracold atoms experiments. However, last year a beautiful extension of Sisyphus cooling has been realized exactly for those unfortunate species for which the usual mechanism fails to work. In my talk I will describe the mechanism, called “grey molasses”, and show the experimental results.

In this talk, I will present our theoretical research on the effect of various magnetic fields (MFs) on the coherence spectra of alkali atoms. The chosen coherent process is Coherence Population Trapping (CPT) which has a wide range of applications. The MFs whose effects have been investigated are static (dc) and oscillating (ac) fields, longitudinal (LMF) and transverse (TMF) to the light propagation direction, as well as a combination of several types of magnetic fields.

The effect of the different MFs has been analyzed both analytically and numerically. I will discuss the contributions of the various subsystems to the total absorption spectra in each case. The different effects of LMF and TMF will be shown and some ways of measuring them will be suggested

Homo- chiral dimers (R - R) and (S - S) and hetero- chiral dimers (R - S) obey opposite selection rules, in regard to their dimer states. Based on that we proposed two simple schemes for purifying scalemic (not 50% - 50%) chiral mixtures.

The first scheme is based on the selective excitation of the target dimers by a single pulse. The second scheme is based on spatial separation of these dimers by a selective laser induced potential. This scheme is executed by a simple coherent control technique, which selectively subjects one of the dimers to a dark (null) potential while the other is subjected to a bright potential. I will present the theoretical background for the selective selection rules of the dimers, and explain the mechanism of selective potentials

Observation of coherent quantum light matter interactions requires that in the medium where the interaction takes place, the de-phasing time is much longer than the time needed for the observation.

In semiconductors, the de-phasing time is determined by scattering processes; at room temperature, it is about 1 ps. Therefore, experiments which probe coherent phenomena are always done at cryogenic temperatures. However, it is also possible, in principle, to sufficiently shorten the observation time so that it is not required to cool the material. This is the approach we have taken in this work which resulted in a direct observation of Rabi oscillations and self-induced transparency in a room-temperature semiconductor laser amplifier.

In this talk I will start by describing an investigation of the dynamical response of InAs/InP nanostructured quantum-dot and quantum-dash (wire-like) gain media following a perturbation of a short 150 fs pulse. In order to study the inhomogeneous nature of the gain broadening, we used a unique ultrafast multi-wavelength pump-probe setup. We then further increase the temporal resolution of our observation up to a few femtoseconds by using a highly sensitive FROG (Frequency resolved optical gating) setup which is capable of measuring the complete electro-magnetic field (phase and amplitude) of the short pulse after propagation. The work is accompanied by an extremely general numerical model of the Maxwell and Schrödinger equations describing the co-evolution of the electronic wavefunction together with the electro-magnetic field and has great novelty in its own right.

With these experimental and theoretical tools we have discovered a novel two-photon induced instantaneous gain mechanism that is also capable of initiating laser oscillations and identify a cascaded four wave mixing process induced of short pulses propagating within a laser. The highlight of the work is the direct observation of the co-evolution of the electronic wavefunction in the semiconductor together with the electro-magnetic field with a nearly single femto-second resolution. These are revealed in the form of Rabi oscillations and self-induced transparency, all occurring at room temperature and at the important optical-communication wavelength of 1.55 um. 

Recent years have seen enormous advancements in the precise fabrication capabilities of micro- and nano-sturctures which led to the emergence of the exciting field of nanophotonics. This is due to the fact that the optical properties of nanostructured materials can be engineered and the interaction between light and matter is strongly affected by encapsulating photons in such structures and materials.  

In my talk I will present some examples of light manipulation by exploiting strong interactions in micro- and nano-structures. I will show how a leaky planar optical waveguide doped with excitonic gain material acts as an optical antenna which radiates quasi-coherent cylindrical vector beams. I will then show that by increasing the oscillator strength of the excitonic material strong coupling between waveguide photons and excitons can be observed. This changes the dynamics of the coupled system and splits its eigenmodes into mixed photon-exciton modes which share properties of light and matter. Finally I will present the development of tunable plasmonic color filters based on the excitation of localized surface plasmons in unique optical nano-antennas and show some of their applications.

website: www.eng.tau.ac.il/~tal/neolab

In this seminar I will review my current research activity and interests. These can be roughly divided into two: Energy, and basic light-matter interaction. On the energy front I will describe recent attempt to combine non-equilibrium thermodynamics with electromagnetics. This research is motivated by the need to find the limiting efficiency of devices whose optics cannot be considered under the approximation of rays. Among such devices are conceptual solar cells that incorporate light management techniques form the realm of nano- and metal-optics. On the second front, namely basic light-matter interaction, I will describe for the first time in public what I believe to be a groundbreaking approach to synthetic nonlinear activity in metal-dielectric composites. This research aims at stronger nonlinear activity with immediate emphasis on second order processes such as sum and difference frequency generation.

I will describe theoretical and experimental studies of mode-locked solid-state lasers, specifically a Kerr-lens mode-locked Titanium:Sapphire laser. This laser is the major source for ultra-short optical pulses, which provides an extremely important tool to investigate ultra-fast processes in physics, chemistry and biology. Specifically, I will present novel cavity designs and configuration, which overcome many of the disadvantages and inherent limitations of standard designed Ti:sapphire optical cavities.

Several experiments will be presented and discussed:

1. Control of vortex array rotation and motion in electromagnetically induced transparency. We demonstrate how the classical optics effect of near-field vortex rotation is modified by the tunable media susceptibility.

2. Phase modulation spectroscopy in EIT media - we measure the electromagnetically induced transparency transmission for a probe with a strongly phase-modulated pump, demonstrating a transition from adiabatic to non-adiabatic response, along with magnetic field dependence.

3. Prospects for single/single photon memory experiments in this system 4. Diffraction from an AC stark-shifted grating of the Rb atoms in the cell.

5. Briefly: Birefringent magnetometry measurements in the SERF regime (high density, high collision rate regime).

 I will introduce the concept of random laser. As an illustration, I will present an innovative mirrorless optofluidic random laser where the optical cavity has been replaced by a random scattering structure. This device serve to show that control can be regained on the random lasing emission. We achieve emission control at any desired wavelength by iteratively shaping the optical pump profile.

I will describe several systems where plasmonic or excitonic nanostructures interact with chiral molecules and circular dichroism (CD) appears in the plasmonic or excitonic resonances.

In particular: the enhancement of CD using plasmonic nanostructures interacting with small quantities of chiral molecules will be described. Size and material dependent study of induction of CD in exciton transitions in colloidal semiconductor quantum dots as a tool to learn on the mechanism of the interaction of the molecules with the dots and about the exciton states. Finally, I will discuss the synthesis and chiroptical properties of nanostructures made of intrinsically chiral materials.

Thousands of papers were published about photonic crystals, namely artificial composites with spatial periodicity. In this talk I will explore the properties and possible realization of temporal photonic crystals (TPCs) with periodicity in time. Specifically, I assume that either the permittivity and/or permeability of a (spatially uniform) medium is a periodic function of time. This gives rise to interesting behavior such as parametric resonances that depend on the thicknes of the dynamic slab and to pulse transmission with faster-than-light partial pulses (that correspond to harmonics of the modulation frequency). Finally, I will show that TPCs can be realized in the microwave regime by means of transmission lines with capacitors (varactors) and/or inductors that are temporally periodic.
 
 

In 1946, Gabor proposed using a lattice of  Gaussians in the time-frequency phase space to provide an intuitive and compact representation of arbitrary signals. The same idea had actually been discovered fifteen years earlier by his countryman von Neumann, in searching for a way to represent arbitrary quantum mechanical wavefunctions in the position-momentum phase space.  Despite the great interest in this approach in both the signal processing and quantum mechanical communities, the method has never succeeded as hoped due to severe convergence problems.  We have recently discovered a simple and surprising solution to the convergence problem, based on introducing periodic boundary conditions into the Gabor/von Neumann lattice. The resulting method provides a simple and compact representation of arbitrary signals and images, and opens the door to unprecedentedly large quantum calculations based on exploiting the underlying classical phase space structure. In the classical limit the method reaches the remarkable efficiency of 1 basis function per 1 eigenstate. We illustrate the method by calculating the vibrational eigenstates of a polyatomic with 10⁴ bound states and by simulating attosecond electron dynamics in the presence of combined strong XUV and NIR laser fields. We also present examples of audio and image compression where we show that the method is competitive with or superior to state-of-the-art wavelet methods.

1. A. Shimshovitz and D. J. Tannor, Phase Space Approach to Solving the Time-independent Schrödinger Equation, Phys. Rev. Lett. 109, 070402 (2012).

2. N. Takemoto, A. Shimshovitz and D. J. Tannor, Phase Space Approach to Solving the Time-dependent Schrödinger Equation: Application to the Simulation and Control of Attosecond Electron Dynamics in the Presence of a Strong Laser Field, J. Chem. Phys. 137, 011102 (2012) (Communication).

3. A. Shimshovitz and D. J. Tannor, Phase Space Wavelets for Solving Coulomb Problems, J. Chem. Phys. 137, 101103 (2012) (Communication).

4. A. Shimshovitz and D.J. Tannor, Periodic Gabor Functions with Biorthogonal Exchange: A Highly Accurate and Efficient Method for Signal Compression, IEEE Signal Processing (submitted);  arXiv:1207.0632 [math:FA]

Dr. Y. Toker / Institute of Physics and Astronomy, Aarhus University, Denmark

*current Address: Department of Particle Physics, The Weizmann Institute of Science

Biochromophores are the molecules used by living organisms in order to interact with visible light. Naturally these molecules are found within proteins, however in order to arrive at a fundamental understanding of their basic properties, our approach is to study the chromophores isolated from their surroundings using action spectroscopy. Recent photo-electron spectroscopy measurements of the Green Flourescent Protein chromophores will be presented, revealing and interesting competition between the different quantum paths available to the chromophore after photo-excitation; as well as photo-fragmentation studies of the Retinal chromophore. These results illustrate the power of action spectroscopy, not only in measuring the absorption bands of isolated ions, but also in studying the dynamics and thermodynamics of these intriguing systems. 

Computer generated holograms afford an interactive and flexible way to modify light beams. In this talk I will describe two different applications of computer generated holograms; holographic optical tweezers, and parallel super resolution STED imaging.
In both applications holograms are created by a spatial light modulator and are used both to shape the beam, align the beam and correct for aberrations. I will conclude with a study of non-equilibrium dynamics done by holographic optical tweezers.
 

Magnetically-tunable Feshbach resonances allow one to change the atom-atom scattering properties in ultracold atomic gases to arbitrary strength and sign, subject only to limitations imposed by the finite temperature of the gas.  Studies of Fermi gases taken directly to the atom-atom scattering resonance have led, among other results, to experimental investigations of BCS-BEC crossover physics which provide direct tests of theories of superconductivity.  However, when bosonic gases are taken to the point of divergent scattering length, rapid three-body recombination limits the lifetime of the gas and can even break the criterion for maintaining thermal equilibrium throughout the ensemble of atoms.

In this talk, I will present recent experimental and theoretical work done at LKB/IFRAF in the group of Christophe Salomon on an ensemble of ultracold lithium-7 taken to a Feshbach scattering resonance.  I will present a measurement of the lifetime of the gas at and around this scattering resonance and provide a framework with which to understand the loss process based on the theoretical work done by our colleagues in the group.  I hope to provide some insight on how to think of three-body losses in the regime where the two-body interaction becomes arbitrarily large.

Recent years have seen enormous advancements in the precise fabrication capabilities of micro- and nano-sturctures which led to the emergence of the exciting field of nanophotonics. This is due to the fact that the optical properties of nanostructured materials can be engineered and the interaction between light and matter is strongly affected by encapsulating photons in such structures and materials.  

In my talk I will present some examples of light manipulation by exploiting strong interactions in micro- and nano-structures. I will show how a leaky planar optical waveguide doped with excitonic gain material acts as an optical antenna which radiates quasi-coherent cylindrical vector beams. I will then show that by increasing the oscillator strength of the excitonic material strong coupling between waveguide photons and excitons can be observed. This changes the dynamics of the coupled system and splits its eigenmodes into mixed photon-exciton modes which share properties of light and matter. Finally I will present the development of tunable plasmonic color filters based on the excitation of localized surface plasmons in unique optical nano-antennas and show some of their applications.

The results of the peculiarities of the electromagnetically induced transparency (EIT) resonance formation when the atomic vapor column is vary in the range of 100 nm up to 1 mm will be presented. Particularly, use of  30-μm-thin cell filled with the Rb and neon gas allows us  to reveal that the  Rb atoms enter the hyperfine Paschen–Back regime in magnetic fields of >1500 G .

            The results on the N –type resonances excited in the Rb atoms confined in a thin cells with variable thickness from 1 μm to 1 mm for the cases of a pure Rb atomic vapor and of a vapor with neon gas admission will be presented. Good contrast and narrow linewidth obtained in 40-μm-thin cell was exploited to study the splitting of the N-type resonance in a magnetic field of up to 2200 G .

Comparison between the EIT- and N-type resonances will be presented.

The interaction of intense light with atoms or molecules can lead to the generation of extreme ultraviolet (XUV) pulses and energetic electron pulses of attosecond (10^-18) duration. The advent of attosecond technology opens up new fields of time-resolved studies in which transient electronic dynamics can be studied with a temporal resolution that was previously unattainable.

I will review the main challenges and goals in the field of attosecond science. As an example, I will focus on a recent experiment where the dynamics of tunnel ionization – one of the most fundamental strong-field phenomena – were studied. Specifically, we were able to measure the times when different electron trajectories exit from under the tunneling barrier created by a laser field and the atomic binding potential. In the following stage, subtle delays in ionization times from two orbitals in a molecular system were resolved. This experiment provides an additional, important step towards achieving the ability to resolve multielectron phenomena -- a long-term goal of attosecond studies.

Fundamental aspects and spectroscopic applications of resonantly driven molecular rotation

Recent advents of intense terahertz field generation have paved the way for nonlinear spectroscopy and coherent control in this unique region of the electromagnetic spectrum. Sub-picosecond terahertz fields resonantly interact with many rotational states simultaneously, and result in repetitive molecular orientation. I will present the fundamental aspects of terahertz induced molecular rotations and its spectroscopic applications, and focus on our recent observation of non-continuous decay profiles of excited rotational populations – a general phenomenon that is revealed in a uniquely pictorial way in a multilevel rotational system.

Time-to-space conversion of ultrafast optical waveforms is one of the less-common techniques employed for the detection of high bit rate optical communications. Although the technique has many virtues, as will be discussed, it is encumbered by a rather complex free-space optical arrangement and low conversion efficiency.

In this talk I will present our recent work on the development of the time-to-space converter, addressing these limitations. These developments lead to our long term goal of realizing the processor in a guided-wave platform. This will enable the processor to become a viable technology, applicable to many ultrafast measurement fields.

Potassium tantalate niobate (KTN) is an oxygen perovskite crystal which at the paraelectric (PE) phase exhibits an exceptionally strong quadratic electrooptical (EO) effect. At temperatures slightly above the ferroelectric (FE) phase transition temperature T_c, KTN manifests an electrically induced change in the refractive index of »10^-2. And yet, this exceptionally strong EO effect has hardly been exploited for applications.

This is partly because of scattering that occur in the vicinity of T_c. Investigations of these scattering phenomena reveal that the EO effect in this region is governed by the interplay between the classical deterministic "crystal optics" mechanism, and the stochastic formation of dipolar clusters that occur in the vicinity of Tc, fluctuating in space and time.

It will be shown how these scattering phenomena affect the EO behavior of KTN, and how they can be inhibited in potassium lithium tantalate niobate (KLTN). It will also be shown how KLTN can be operated at visible wavelengths without developing optical damage due to the formation of random space charge.

The photorefractive (PR) effect at the paraelectric phase in the vicinity of Tc will then be discussed, and its use for electroholography will be shown. Electroholographic diffraction with wide range electric tunability of the Bragg condition will be demonstrated. Emloying this phenomenon for the implementation of a laser with electric tunability through the entire C band.

The effect of the dipolar clusters on beam propagation in photorefractive KLTN will then be discussed, in particular, diffractionless propagation in minute reduced refractive index tunnels formed by fast quenching of the dipolar clusters to freeze spatial solitons.

Finally, a generic fabrication technique of 3D structures with sub-wavelength dimensions and reduced refractive index based on the implementation of fast ions in a KLTN substrate will be presented, and its potential for the construction of complex EO integrated circuits in which multitudes of EO devices and photonic structures are interconnected by a mesh of waveguides and operate in unison.

X-ray free-electron lasers operating in the angstrom regime have recently become available. These new systems, which deliver femtosecond-scale pulses with peak intensity exceeding 10¹⁸ W/cm², open the path to new experiments in the field of nonlinear optics at x-ray wavelengths. Recently, we have observed phase-matched x-ray second harmonic generation of a pump beam at 1.7 Å. I will describe the experiment, and the theory of second order nonlinearity at x-ray wavelengths. I will discuss future directions, including the possibility of using second harmonic generation as a temporal correlator for diagnostics of ultrafast phenomena in the x-ray regime.

Quantum nano- optics devices are likely to become primary components of future electronic devices. Practical realization of quantum devices faces a number of challenges. However, the benefits from the successful implementation of these devices can be enormous. Nature in several cases uses quantum mechanics in order to achieve extraordinary properties. One known examples is the high photon conversion efficiency in photosynthetic light harvesting complexes. In this example the most striking feature is the use of coherence properties and quantum mechanics in the short scale while the measurements and results are classical in the large scale. In my lab we aim to mimic nature and create nano tool box bottom up approach which enables high temperature quantum operation coupled to top down classical semiconductor measurement device (See [1] for example).

This methodology is producing a generic technology for constructing nano-systems in which many devices are interconnected and operate in unison, without inhibiting their quantum nature. In the talk we will present our efforts to achieve confinement potential control using different dots systems [2,3] as well as charge and spin transfer control in our hybrid dots systems [4]. We will show our recent results in which we were able to discover a collective electron transfer process by studying the current noise in a field effect transistor with light-sensitive gate formed by nanocrystals linked by organic molecules to its surface [5]. A demonstration of a room temperature operating hybrid quantum sensor will be presented, together with antennas for enhancing the efficiency of solar cells.

 We hope that by controlling the quantum and classical behavior of the self assembled layers we will be able to create novel and revolutionary devices mimicking some of Nature's complex structures. One such example would be mimicking the light harvesting complexes in a controlled self assembled design. Using the flexibility of the design we can realize systems which will test the some of the suggested quantum theories. Further into the future we aim to use this knowledge for applicable devices such as increasing the efficiency of solar cells coupled to simple Si based devices.

[1] N. Livneh et al. Nano Lett. 11, 1630 (2011).

[2] S. Shusterman et al. Europhys Letters 88 (2009) 66003.

[3] D. P. Kumah et al. Nature Nanotechnology 4 (2009) 835.

[4] T. Aqua   et al. Appl. Phys. Lett. 92  (2008) 223112.

[5] Y. Paltiel et al.  Phys. Rev. Lett. 104, 016804 (2010).

Stimulated Brillouin scattering (SBS) is a nonlinear interaction between a relatively intense pump wave, and a counter-propagating, spectrally detuned probe wave. When the difference between the optical frequencies of the two waves matches the Brillouin frequency shift of the medium W_B, the probe wave may be amplified at the expense of the pump. SBS is readily observed in standard silica single-mode fibers over lengths of hundreds of meters.

Chalcogenides (ChGs) are a family of glasses which contain one of the chalcogen elements (e.g. S, Se, or Te). They have a broad transparency window from the visible to the mid-infrared wavelengths, and are well known for their highly-nonlinear refractive index n₂, that is up to thousand times greater than that of silica. The large nonlinearity makes ChGs an attractive platform for all-optical signal processing. Nonlinear propagation effects in waveguides written in ChG glass have been used in four-wave-mixing, in wavelength conversion etc.

Recently, SBS amplification was demonstrated in 7 cm-long As₂S₃ waveguides, defined using a dry-etch process. In this work, we report SBS amplification in As₂S₃ waveguides defined by a much simpler technique of direct laser-beam writing. 1 cm-long and 4 mm-wide waveguides were patterned in a 1 mm-thick film of As₂S₃, deposited on a silica-on-silicon substrate. The results provide the first demonstration of SBS amplification in directly-written chalcogenide glass waveguides. The observed gain bandwidth of 200 MHz is considerably wider than previously reported values of ~30MHz. A possible explanation due to multi-mode behavior along with the longitudal evolution of the optical field profile will be discussed.

Monitoring Tissue Blood Flow is vital during states of decreased or increased flow. However, there are currently no non-invasive devices that measure microcirculatory blood flow in tissue continuously. This talk will present a novel device that uses Ultrasound Modulation of Diffused Light to perform non-invasive monitoring of blood flow at the microcirculatory level underneath its sensor.

We demonstrate the ability of Ornim's device ( the CerOx) to monitor tissue blood flow in various situations. The ability to monitor critical processes such as autoregulation in the brain and its clinical importance are shown.

Measurement of vibrational dynamics in molecules is key to the understanding of chemical processes, such as the evolution of chemical reactions, and to the ability to control them. Current methods, such as molecular tomography or pump-probe techniques generally suffer from a very low signal per molecule (1 photon or less), limiting their sensitivity and applicability. I will describe a method to coherently amplify the signal per molecule using a coherent Raman oscillator that is synchronously pumped by an optical frequency comb, thereby improving the sensitivity of detection by orders of magnitude.

By placing the molecules in an optical cavity that is synchronously pumped by a frequency comb laser source, the emission from the molecular excitation of one pulse returns to the molecule in phase with subsequent excitations and can be amplified by stimulated emission. The cavity can therefore serve as a memory that maintains the coherent emission between the pulses, enabling amplification by stimulation of the emitted signal per molecule. As we have recently shown in extensive simulation and calculation, this coherent amplifier can easily cross the oscillation threshold, producing short bursts of strong optical pulses that directly represent the wave-packet dynamics initiated by the pump pulses in the excited electronic potential.

Such an oscillator will improve the signal to noise ratio of measurements by several orders of magnitude compared to standard techniques and may open avenues for analysis of chemical reactions in the femtosecond time scale. Since here, the cavity serves as the coherent memory and not the molecules themselves, the scheme operates well also when the molecular coherence times are short; i.e. with molecules in hot / room temperature conditions, and also in solution / on surface, which broadens the scope of applicability significantly.

I will describe our (so far theoretical) research of this unique Raman oscillator , its fascinating coherence properties and the experiments we plan to perform with it.

Abstract:  High resolution ranging systems are of great importance for both civilian and military applications. Both radio frequency (RF) waveforms and optical waveforms (LADAR) are used for range detection purposes. In both techniques, high range resolution can be obtained using short and intense pulses. However, the transmission and processing of such pulses is difficult and potentially unsafe. Instead, temporally extended waveforms or sequences, in conjunction with proper compression techniques at the receiver end, may be used. The instantaneous power of the extended waveforms can be orders-of-magnitude lower, making them safer and simpler to generate in a real-world system and more difficult to intercept by an adversary.

In this work, I propose and demonstrate two distinct schemes for high resolution ranging measurements. The first proposition is a microwave-photonic, ultra-wideband (UWB) noise RADAR system. The system makes use of the amplified spontaneous emission (ASE) of optical amplifiers to generate random 'physical noise' that is later converted to the RF domain. The system comprised of a central unit and remote end unit that were separated by 10 km of fiber. A range resolution of 10 cm was achieved using this system.

The second technique is a LADAR system, employing an encoded sequence of pulses and a proper post-processing to obtain high resolution ranging measurements with low sidelobes. A novel compression scheme, previously proposed by Prof. Nadav Levanon of Tel-Aviv Univ., was employed in the experiment. The method achieved the sidelobe suppression of complex coherent receivers, even though a simple direct detector was employed. A ranging resolution of 3 cm was obtained.