Quantum Wavelength Conversion with Bulk Acoustic Waves

Abstract: 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. We discuss the design challenges of building the cryogenic optomechanical cavity, in particular thermal misalignment and isolation against dilution refrigerator vibrations, and present our first observation of optomechanical coupling and mode thermometry. We also detail our strategy for minimizing the amount of stray optical radiation that impinges on the superconductor. We show results from an experiment that studies quasiparticle generation due to laser light and its detrimental effects on our microwave circuitry.