Boron-Vacancy/Carbon Defect in the Two-Dimensional Hexagonal Boron Nitride as a spin qubit

Using existing knowledge and an educated guess we select a neutral defect in the hexagonal boron nitride (hBN), which consists of a boron vacancy combined with a carbon dopant substituting another boron atom (V_BC_B), as a possible optically controllable spin qubit. Our calculations confirmed that V_BC_B has triplet ground state and singlet local energy minimum. Both states are dynamically stable according to our phonon calculations. Next, we applied the advanced linear response GW and Bethe-Salpeter equation methods to calculate the electronic structure and optical excitations in the triplet and singlet states. Using our calculation results, we constructed the spin-polarization cycle diagram for the V_BC_B defect and found it to be a promising spin qubit.