Towards high-fidelity charge state control of the NV center at 100 K

The nitrogen-vacancy (NV) center in diamond is a promising platform for quantum technologies. Low temperature (<10 K) experiments have shown the suitability of the color center for quantum communication, sensing, simulation and computation. Remarkably, the NV center allows for room temperature as well, though the electron spin relaxation time poses a limit to the electron spin coherence. We performed experiments at 100 K, a temperature at which the relaxation time of the electron spin of the NV center is long (>1 s) compared to room temperature, while cooling is much less demanding than for reaching the commonly studied regime of <10 K.

Ionization of the NV center from its negative charge state to its neutral form, limits efficiency of the system. Therefore, we have explored and implemented different methods for optical readout and initialization of the charge state of a naturally occurring NV center in an isotopically purified <100> diamond sample. A previously developed model for charge state dynamics of the NV center under 637 nm laser illumination by Shields et al. [1] was adapted and used to quantify and improve the charge state readout at 100 K. Furthermore, we implemented optical charge state initialization. The tools that we developed pave the way for charge state control of the NV center at 100 K, an important prerequisite for eventual operation of an NV center based quantum processor at high temperatures.

[1] B. J. Shields et al. Phys. Rev. Lett. 114, 136402 (2015).