Rapid, in-situ neutralization of nitrogen- and silicon-vacancy centers in diamond using above-band-gap optical excitation

The charge state of a quantum point defect in a solid-state host strongly determines its optical and spin characteristics. Consequently, techniques for controlling the charge state are required to realize technologies such as quantum networking and sensing. In this work we demonstrate the use of deep- ultraviolet (DUV) radiation to dynamically neutralize nitrogen- (NV) and silicon-vacancy (SiV) centers. We first examine the conversion between the neutral and negatively charged NV states by correlating the variation of their respective spectra, indicating that more than 99% of the population of NV centers can be initialized into the neutral charge state. We then examine the time dynamics of bleaching and recharging of negatively charged SiV⁻ centers and observe an 80% reduction in SiV⁻ photoluminescence within a single 100-μs DUV pulse. Finally, we demonstrate that the bleaching of SiV⁻ induced by the DUV is accompanied by a dramatic increase in the neutral SiV⁰ population; SiV⁰ remains robust to extended periods of near-infrared excitation despite being a non-equilibrium state. DUV excitation thus presents a reliable method of generating SiV⁰, a desirable charge state for quantum network applications that is challenging to obtain by equilibrium Fermi engineering alone. Our results on two separate color centers at technologically relevant temperatures indicate a potential for above-band-gap excitation as a universal means of generating the neutral charge states of quantum point defects on demand.