It was noted that a precise read-out of spin states was crucial for any approach towards physical realization of a spin-based quantum computer and for magnetometry with single spins. Here, a method was described by which to improve greatly the optical read-out fidelity of electron spin states associated with single nitrogen-vacancy centers in diamond. The signal-to-noise ratio was enhanced significantly by performing conditional flip-flop processes between the electron spin and the nuclear spin of the nitrogen-vacancy center’s nitrogen atom. The enhanced readout procedure was triggered by a short preparatory pulse sequence. As the nitrogen nuclear spin was intrinsically present in the system, this method was universally applicable to any nitrogen-vacancy center. Besides the read-out method, these studies included coherent control over a single nitrogen nuclear spin for the first time.

Universal Enhancement of the Optical Readout Fidelity of Single Electron Spins at Nitrogen-Vacancy Centers in Diamond. M.Steiner, P.Neumann, J.Beck, F.Jelezko, J.Wrachtrup: Physical Review B, 2010, 81[3], 035205