Microwave single-photon detection using a hybrid spin-optomechanical quantum interface

Microwave single-photon detection is an enabling technology for quantum state readout and for exotic particle detection. However, the low energy scales of microwave photons make their detection challenging. Here, we propose a hybrid spin-optomechanical interface to detect single microwave photons. The microwave photons are coupled to a phononic resonator via piezoelectric actuation. This phononic cavity is embedded with Silicon-vacancy (SiV) centers in diamond, which are used for readout. Phonons mediate the quantum state transfer of the microwave cavity to the SiV spin. From this, single-shot or dispersive shift readout is used to detect the single photon. Starting with a set of experimentally realizable parameters, we simulate the complete protocol and estimate an overall detection success probability over 90%, Shannon's mutual information exceeding 0.57 ln(2), which positions our device at the forefront of microwave single-photon detection.