Incorporating single-photon counting with an efficient electro-optic transducer (part I)

A sufficiently efficient and low-noise transducer linking microwave and optical frequencies would enable entanglement between superconducting quantum registers separated by long distances. In the presence of inevitable transmission losses, single-photon detection can be leveraged to trade success probability for improved fidelity of such entanglement. We present the experimental incorporation of optical photon counting with a high-efficiency transducer. This transducer links microwave and optical fields via simultaneous coupling to the same mechanical mode of a MHz-frequency silicon nitride membrane. We demonstrate the implementation of single-photon detection to characterize the transducer while operated with its mechanical mode close to the ground state. Part I of this presentation focuses on the single-photon counting measurement apparatus.