Deterministic single-phonon-to-photon quantum transducer for distributed quantum networks

Quantum transducers are essential for connecting hybrid quantum systems with distinct frequencies, pivotal for hybrid quantum networks. A deterministic quantum transducer protocol is proposed for the upconversion of single phonons in the microwave domain to optical photons. Utilizing a hybrid optomechanical crystal coupled to a three-level emitter, the protocol deterministically upconverts an itinerant phonon into an optical photon, when an auxiliary optical cavity mode is driven by a single photon. Furthermore, the deterministic upconversion transducer can also be achieved by driving the emitter with a classical laser pulse, rather than driving the optical cavity with a single photon. The intracavity photon numbers in both protocols are significantly less than one during the operation, thus overcoming the problem of parasitic heating within radiation-pressure coupling of hybrid optomechanical systems. These outstanding features make the protocols particularly useful for the realization of large-scale distributed hybrid quantum networks.