Coherent microwave single-photon source for a mechanically mediated electro-optic transducer

A low-noise and highly efficient transducer is a crucial piece to interface two superconducting qubits from distant places. However, generating a high-coherence quantum state matched to the transducer’s kHz bandwidth is quite challenging since it requires a long pulse duration. In this talk, I will present our experimental effort to build a coherent quantum source for our mechanically-mediated transducer. This single-photon source comprises two 3d cavities and a transmon qubit, and the transmon both provides the nonlinearity for generating single-photon state and acts as a four-wave mixing element for swapping the quantum state between these two cavities.