Fast optoelectronic charge state conversion of silicon vacancies in diamond

Group IV vacancy color centers in diamond are promising spin-photon interfaces with strong potential for applications for photonic quantum technologies. Reliable methods for controlling and stabilizing their charge state are urgently needed for scaling to multi-qubit devices. Here, we manipulate the charge state of silicon vacancy (SiV) ensembles by combining luminescence and photo-current spectroscopy. We controllably convert the charge state between the optically active SiV^- and dark SiV^2- with MHz rates and >90% contrast by judiciously choosing the local potential applied to in-plane surface electrodes and the laser excitation wavelength. We observe intense SiV^- photoluminescence under hole-capture, measure the intrinsic conversion time from the dark SiV^2- to the bright SiV^- to be 36.4(6.7)ms and demonstrate how it can be enhanced by a factor of 10⁵ via optical pumping. Moreover, we obtain new information on the defects that contribute to photo-conductivity, indicating the presence of substitutional nitrogen and divacancies.