Optically Active Single Hole Spin in ZnSe.

Semiconductor hole spins offer a pathway to extended coherence times by decoupling from nuclear magnetic noise, while their spin-orbit coupling enables fast all-electrical control. In ZnSe, however, realizing this potential has been limited by p-doping challenges. Here, we circumvent this limit by optically activating acceptors and demonstrate optical spin initialization. We isolate a single-hole spin bound to a shallow acceptor, confirmed by antibunching and accessed via the fast (244 ps) radiative recombination of a bound exciton. Magnetic and Raman spectroscopy reveal a spin-selective Λ system with an effective hole g-factor of 0.7 and an optical line width of 26.7 GHz. Time-resolved measurements reveal optical pumping of the hole spin with an estimated initialization fidelity of 90.7%. First-principles simulations combined with the experiment identify nitrogen as the most likely acceptor impurity. These results introduce a promising new platform for optically active spin qubits and single-photon sources in ZnSe.