  We demonstrate the super-resolution localization of the nitrogen vacancy
centers in diamond by a novel fluorescence photoswitching technique based on
coherent quantum control. The photoswitching is realized by the quantum phase
encoding based on pulsed magnetic field gradient. Then we perform
super-resolution imaging and achieve a localizing accuracy better than 1.4 nm
under a scanning confocal microscope. Finally, we show that the quantum phase
encoding plays a dominant role on the resolution, and a resolution of 0.15 nm
is achievable under our current experimental condition. This method can be
applied in subnanometer scale addressing and control of qubits based on
multiple coupled defect spins.
