Optimal control theory techniques for nitrogen vacancy ensembles in single crystal diamond

Nitrogen vacancy centre ensembles are excellent candidates for quantum sensors due to their vector magnetometry capabilities, deployability at room temperature and simple optical initialization and readout. This work describes the engineering and characterization methods required to control all four principle axis systems (P.A.S.) of NV ensembles in a single crystal diamond without an applied static magnetic field. Circularly polarized microwaves enable arbitrary simultaneous control with spin-locking experiments and collective control using optimal control theory (OCT) in a (100) diamond. These techniques may be further improved and integrated to realize high-sensitivity NV-based quantum sensing devices using all four P.A.S. systems.