Generation and applications of quantum light using structured nonlinear crystals and shaped pump beams

In spontaneous parametric down conversion, a pump photon spontaneously splits inside a quadratic nonlinear crystal to signal and idler photons. By spatially modulating the nonlinear coefficient and/or structuring the pump, it is possible to shape the correlations of the down-converted signal and idler photons in either the spatial domain or the spectral domains. These degrees of freedom span a multi-dimensional Hilbert space, hence they offer advantages for quantum information applications. Specifically, we have fabricated structured nonlinear crystals for directly generating spatially entangled signal-idler pairs, including a bi-photon Bell state in the Hermite-Gauss basis [1]. In the spectral domain, structured crystals and shaped pumps enabled us to generate a variety of quantum states such high purity frequency uncorrelated states, frequency-bin Bell states and frequency entangled bi-photon qudit states [2].

The generated light is useful for quantum sensing applications. Recently [3] we have demonstrated quantum sensing of mechanical rotation using a high flux N00N state with N=2. This setup enables to measure the rotational Doppler shift of slowly rotating objects, at rates that are comparable to Earth's spin. We believe that this method paves the way for high resolution and high sensitivity quantum sensors based on structured quantum light.

[1] O. Yesharim, S. Pearl, J. Foley-Comer, I. Juwiler, and A. Arie, “Direct generation of spatially entangled qudits using quantum nonlinear optical holography,” Science Advances 9, eade7968 (2023).

[2] A. Shukhin, I. Hurvitz, S. Trajtenberg-Mills, A. Arie, and H. Eisenberg, "Two-dimensional control of a biphoton Joint Spectrum," Optics Express 32, 10158 (2024);

[3] O. Yesharim, G. Tshuva, A. Arie, "Quantum enhanced mechanical rotation sensing using wavefront photonic gears," APL Photonics 9, 106116 (2024)