Quantum optomechanical control of long-lived bulk acoustic phonons

High-fidelity quantum optomechanical control of a mechanical oscillator requires the ability to perform efficient, low-noise operations on long-lived phononic excitations. Microfabricated high-overtone bulk acoustic wave resonators (μHBARs), which are Fabry-Perot resonators for sound waves, have been shown to support high-frequency (> 10 GHz) mechanical modes with exceptionally long coherence times (> 2.5 ms), making them a compelling resource for quantum optomechanical experiments. We demonstrate a new optomechanical system that permits quantum optomechanical control of individual high-coherence phonon modes supported by such μHBARs for the first time. We use this system to perform laser cooling of such ultra-massive (7.5 μg) high frequency (12.6 GHz) phonon modes from a thermal occupation of ∼22 to fewer than 0.4 phonons, corresponding to laser-based ground-state cooling of the most massive mechanical object to date. Through these laser cooling experiments, no absorption-induced heating is observed, demonstrating the resilience of the μHBAR against parasitic heating. The unique features of such μHBARs make them promising as the basis for a new class of quantum optomechanical systems that offer enhanced robustness to decoherence, necessary for efficient, low-noise photon-phonon conversion.

 

In my talk, I will present our system and its operation principles and discuss its unique features and promising results for future optomechanical experiments and technologies. I will also discuss the extension of our system to different materials, e.g. Diamonds, where the excellent phonons' coherence may be utilized to modulate transitions in color centers, and/or mediate between them and telecom photons.