Cavity piezo-mechanics for microwave-to-optical conversion*

Hybrid quantum systems are essential for realizing distributed quantum networks. In particular, GHz-piezo-mechanics, which features low thermal excitations and strong couplings to both microwave and optical modes, offers an appealing platform to bridge superconducting quantum processors and optical telecommunication channels. However, integrating superconducting and optomechanical elements at cryogenic temperatures remains a challenge. Here, we report an integrated superconducting cavity piezo-optomechanical platform where 10-GHz phonons are resonantly coupled with photons in a superconducting cavity and a nanophotonic cavity simultaneously. With the large piezo-mechanical cooperativity (Cem∼7) and the enhanced optomechanical coupling boosted by a pulsed optical pump, we demonstrate coherent interactions at cryogenic temperatures via the observation of efficient microwave-optical photon conversion. This hybrid interface makes a substantial step towards quantum communication at a large scale, as well as novel explorations in microwave-optical photon entanglement and quantum sensing mediated by gigahertz phonons.