Three-dimensional system design and material characterization for microwave-optical quantum transduction*

Quantum transduction allows for the interconnection between cryogenic superconducting quantum computers and room-temperature optical quantum communication systems. Here we present our progress in realizing a three-dimensional microwave-optical transducer based on a long-coherence-time superconducting cavity integrated with an electro-optic optical resonator. We engineer the cavity geometry for optimized microwave-optical coupling and characterize the microwave properties of electro-optic materials at cryogenic temperature. Such a scheme enables large electro-optic coupling strength with low microwave and optical losses, thus leading to high-efficiency quantum transduction operating at relatively low optical pump power. We envision that the efficient transducer can be exploited for optical readout of superconducting qubits, remote entanglement generation, and high-precision quantum sensing.