High-frequency cavity optomechanics using bulk acoustic phonons

TL;DR

This paper demonstrates high-frequency (13 GHz) phonon modes in macroscopic systems for robust quantum operations, overcoming heating issues in micro-scale optomechanical systems by leveraging bulk acoustic phonons in centimeter-scale structures.

Contribution

It introduces a novel approach to access high-frequency phonons in macroscopic systems, enabling quantum operations with larger motional masses and reduced heating effects.

Findings

Achieved resonant coupling between optical cavity modes via bulk acoustic phonons.

Performed beam-splitter and entanglement operations at MHz rates.

Showcased potential for quantum memories and microwave-to-optical conversion.

Abstract

To date, micro- and nano-scale optomechanical systems have enabled many proof-of-principle quantum operations through access to high-frequency (GHz) phonon modes that are readily cooled to their thermal ground state. However, minuscule amounts of absorbed light produce excessive heating that can jeopardize robust ground state operation within such microstructures. In contrast, we demonstrate an alternative strategy for accessing high-frequency ($13$ GHz) phonons within macroscopic systems (cm-scale). Counterintuitively, we show that these macroscopic systems, with motional masses that are $>20$ million times larger than those of micro-scale counterparts, offer a complementary path towards robust quantum operations. Utilizing bulk acoustic phonons to mediate resonant coupling between two distinct modes of an optical cavity, we demonstrate the ability to perform beam-splitter and entanglement operations at MHz rates on an array of phonon modes, opening doors to applications ranging from quantum memories and microwave-to-optical conversion to high-power laser oscillators.