Efficient Photon Conversion in a Scalable Microwave-to-Optics Transducer

Exchanging quantum information between microwave and optical frequencies allows for flexible handling of quantum states, in particular using the reach and room-temperature operation of optical-frequency quantum networks to scale the size of microwave-frequency quantum processors. Nevertheless a transducer that can form useful quantum links between these vastly separate frequencies must meet a number of stringent conditions: the transducer must add less than a single quantum of input referred noise and operate with high efficiency over a large bandwidth at a high repetition rate. Also, in order to scale to a useful size, the transducer must be fully integrated. We present the operation of a new design for an integrated transducer fabricated from lithium niobate on silicon-on-insulator. By combining the strong piezoelectric coupling of the former with the large refractive index of the latter, we realise efficient microwave-to-optics transduction mediated by a confined mechanical excitation [1].