Resonant Optical Spin Initialization and Readout of Single Silicon Vacancies in 4H-SiC

The silicon vacancy in SiC has long-lived electronic spin states that can be used for quantum sensing, communication, and computation, but knowledge of the optical transitions used to measure and control these spin states has been lacking. This study uses high-resolution laser spectroscopy of individual silicon vacancies in 4$H$-SiC to isolate the spin-dependent optical transitions. Each defect has two narrow, nearly lifetime-limited optical transitions that correspond to different spin states, and result in quite different spin-polarization dynamics when driven. These results are promising for interfacing spins and photons, including efficient spin initialization and readout.