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

The silicon monovacancy in 4H-SiC is a promising candidate for solid-state quantum information processing. We perform high-resolution optical spectroscopy on single V2 defects at cryogenic temperatures. We find favorable low-temperature optical properties that are essential for optical readout and coherent control of its spin and for the development of a spin-photon interface. The common features among individual defects include two narrow, nearly lifetime-limited optical transitions that correspond to m(s) = +/- 3/2 and m(s) = +/- 1/2 spin states with no discernable zero-field-splitting fluctuations. Initialization and readout of the spin states are characterized by time-resolved optical spectroscopy under resonant excitation of these transitions, showing significant differences between the +/- 3/2 and +/- 1/2 spin states. These results are well described by a theoretical model that strengthens our understanding of the quantum properties of this defect.