Progress toward entangling superconducting qubits with room temperature optical photons: Part I

Quantum transducers provide a pathway to link superconducting circuits to quantum networks that extend over large distances at ambient temperatures. Here, we present our progress toward entangling a superconducting qubit in a dilution refrigerator with a time-bin encoded optical qubit propagating through a room temperature telecom fiber. Starting from a transmon qubit coupled to a microwave resonator, we generate an itinerant time-bin encoded microwave qubit entangled with the transmon. We then route the microwave photon to an electro-optic transducer that upconverts it to the optical domain. To verify the entanglement fidelity, we perform simultaneous measurements of the superconducting qubit and the optical qubit states, and we show evidence of correlations in both longitudinal and transversal bases.

In this part of the two-part talk, we describe the microwave side of the experiment. We present current experimental results, and discuss solutions for some of the challenges faced in the microwave domain. Our findings highlight the feasibility of using electro-optic conversion to interface superconducting qubits with photonic channels for quantum networking.