Aluminum vacancy/sulfur complex in wurtzite AlN as an optically controllable spin qubit

Using our rational methodology, we reveal a defect in wurtzite AlN that can serve as an optically controllable spin qubit. It combines an Al vacancy and a S atom substituting the neighboring N atom (VAlSN). Linear response GW and Bethe-Salpeter equation calculations guide us to find suitable ground and excited triplet and singlet states of VAlSN. The obtained optical spin-polarization cycle is similar to that observed in the negative nitrogen-vacancy (NV^-) center in diamond. The calculated optical oscillator strengths for VAlSN suggest that, in contrast to the NV^- center, the optical emission in the singlet and triplet states have comparable rates, which is favorable for the qubit functionality.