Probing ground-state mechanical modes using the silicon vacancy center in diamond

The Silicon Vacancy (SiV) center in diamond has shown promise for use in quantum networking due to its long-lived spin and demonstrated high-cooperativity spin-photon interface. In addition to its excellent optical interface, the SiV center also exhibits a large susceptibility to acoustic phonons. While this susceptibility is typically considered a drawback for necessitating low-temperature operation, it also enables the SiV center to act as a sensitive probe of its acoustic environment. We engineer this acoustic environment by embedding an SiV center within a diamond optomechanical crystal cavity (OMC). The optical cavity mode of this OMC is designed to be resonant with the SiV optical transition (737 nm), enabling highly efficient readout of the SiV spin state. The OMC also supports GHz-range mechanical modes, enabling resonant interactions with the spin transition of the SiV center. We show that we can use these SiV center couplings to perform sub-pW optical readout of mechanical cavity modes. This demonstration paves the way towards the SiV center in diamond serving as a powerful intermediary between microwave and optical quantum systems.