Bulk Acoustic Quantum Transduction II: A Brillouin Optomechanical Cavity at mK Temperatures

A low-noise, efficient, bi-directional microwave-to-optical transducer could connect superconducting circuits in distant dilution refrigerators, offering a promising route towards powerful, large-scale quantum computers and networks. We present our advances in developing a device in which a Bulk Acoustic Wave (BAW) resonator mediates interactions between the microwave field of a transmon qubit and a telecom-frequency mode of a Fabry-Perot cavity. Strong electromechanical [1] and optomechanical [2] coupling to BAW modes have been demonstrated in individual experiments; now our goal is building a single device capable of both.

In this talk, we discuss our development of an optomechanical cavity for operation inside a dilution refrigerator, designed to be compatible with coupling to superconducting circuits. We discuss the design challenges, in particular isolation against fridge vibrations, and present our first observation of optomechanical coupling. Finally, we discuss our mode thermometry results in this system.