  As a potential candidate for quantum computation and metrology, the nitrogen
vacancy (NV)center in diamond presented both challenges and opportunities
resulted from charge state conversion. By utilizing different lasers for the
photon-induced charge state conversion, we achieved the sub-diffraction charge
state manipulation. The charge state depletion (CSD) microscopy resolution was
improved to 4.1 nm by optimizing the laser pulse sequences. Subsequently, the
electron spin state dynamics of adjacent NV centers were selectively detected
via the CSD. The experimental results demonstrated that the CSD can improve the
spatial resolution of the measurement of NV centers for nanoscale sensing and
quantum information.
