Bulk Acoustic Quantum Transduction I: Designing an Optical Interface for Superconducting Qubits*

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.

One of the main challenges of implementing this strategy is minimizing the amount of stray optical radiation that impinges on the superconductor, which generates quasiparticles that cause qubit decoherence. We demonstrate a technique for aligning the optical mode to the BAW resonator near the qubit. We also present our first results from an experiment that studies the detrimental effects of laser light on our microwave circuitry.

  

[1] von Lüpke et al. (2021) arXiv:2110.00263

[2] Kharel et al. (2019) arXiv:1812.06202