We present our recent progress in implementing an improved readout scheme for the nitrogen-vacancy (NV) center's spin-state combining resonant excitation at low (4 Kelvin) temperature with spin-to-charge conversion. Resonant excitation exploits that the optical excitation spectrum at low temperature has sufficiently narrow linewidths[1,2] to selectively address the spin-sublevels. In combination with a second laser pulse, a spin-to-charge conversion[3,4] protocol can be implemented, where the NV center is spin-selectively excited and converted to different charge-states. These are more stable than the initial spin-state and can be read-out with single-shot fidelity, even by inefficient collection optics.
Compared to the state-of-the-art readout, this work promises to accelerate readout by a factor of up to 100. Besides, laser power in the optical regime can be reduced, which lowers the risk of photodamage for future sensing experiments with biological samples.
We expect our scheme to become a core enabling tool for single-molecule electron spin resonance detected by NV centers.
 A. Batalov, Physical Review Letters 102, 195506 (2009)
 M.W. Doherty, New Journal of Physics 13, 025019 (2011)
 B.J. Shields, Physical Review Letters 114, 136402 (2015)
 X.-D. Chen, Physical Review A 7, 014008 (2017)
 D.A. Hopper, Micromachines 9, 437 (2018)
This project has received support from DFG via projects SPP1601 and RE3606/3-1.