Charge state instabilities in shallow NV centers for quantum sensing

Presenting Author: Mattias Fitzpatrick, Princeton University
Contributing Author(s): Zhiyang Yuan, Nathalie P. de Leon

Nitrogen Vacancy (NV) centers in diamond are a promising platform for nanoscale sensing, quantum information processing, and quantum networks. For most sensing applications, due to the decay of target signal outside the diamond, it is advantageous to have NV centers as close as possible to the diamond surface. However, it has been observed that for shallow NV centers, the measurement contrast for Rabi experiments and optically detected magnetic resonance (ODMR) is worse than that for bulk NV centers. Here we demonstrate that the degradation of shallow NV centers Rabi and ODMR contrasts can be associated with dynamics between the two charge states of the NV center (NV$^0$ and NV$^-$). We validate this claim by comparing two distinctly different diamond samples with shallow NVs, one which has charge-state stable NVs and the other with measurably less stable NVs. We measure NV spectra to compare the equilibrium charge state population for NVs in these two samples. Charge state conversion measurements are performed to extract the ionization and recombination rates in the dark and under both green (\unit{532}{\nano\meter}) and orange laser (\unit{590}{\nano\meter}) illumination. Finally, to understand how the charge state population and dynamics are influencing the ESR contrasts, we use time-resolved measurement of NV fluorescence and develop a model of the spin states of NV$^-$ and the NV$^0$ charge state. By fitting the measured fluorescence as function of time to our model, we deduce that the primary cause for lower ESR and Rabi contrast is an increase in the NV$^0$ population and rapid spin-nonconserving charge state conversion at higher laser powers. This research was supported by an appointment to the Intelligence Community Postdoctoral Research Fellowship Program at the Princeton University by Oak Ridge Institute for Science and Education (ORISE) through an interagency agreement between the U.S. Department of Energy and the Office of the Director of National Intelligence (ODNI).

(Session 4 : Saturday from 4:30pm - 5:00pm)


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