The silicon vacancy centers in SiC: determination of intrinsic spin dynamics for integrated quantum photonics

The negatively charged silicon vacancy center (V−s) in silicon carbide (SiC) is an emerging color center for quantum technology covering quantum sensing, communication, and computing. Yet, limited information on the internal spin–optical dynamics prevents optimal operation and maximum performance, especially when integrated within quantum photonics. Here, we establish the intrinsic spin dynamics of the V−s center at the cubic lattice site (V2) in 4H-SiC via in-depth electronic fine-structure modeling including intersystem-crossing (ISC) and deshelving mechanisms. With carefully designed spin-dependent measurements, we determine previously unknown spin-selective radiative and non-radiative decay rates and identify the ISC mechanism. Using the obtained rates, we propose a realistic implementation for time-bin entangled multi-photon GHZ and cluster state generation, finding that up to three-photon states are within reach using existing nanophotonic cavity technology. We provide estimates for quantum efficiencies, state fidelities, optimal pulse timings, and minimum cavity-enhancement requirements. The approaches and insights are directly applicable to other color centers and their benchmarking for specific applications.