Entangling separate nitrogen-vacancy centers in a scalable fashion via coupling to microtoroidal resonators

We propose a potentially practical scheme to entangle negatively charged nitrogen-vacancy (N-V) centers in distant diamonds. Each diamond is supposed to be fixed on the exterior surface of a microtoroidal resonator, and the single-photon input-output process—a currently available technique—could entangle separate N-V centers in a scalable fashion. The feasibility of our scheme and the experimental challenge are discussed by considering currently available techniques for qualified N-V centers and cavities.