Tunable charge states of nitrogen-vacancy centers in diamond for ultrafast quantum devices

A prerequisite condition for next-generation quantum sensing, communication, and computing is the precise modulation of the charge states of nitrogen-vacancy (NV) centers in diamond. We have achieved tuning of these centers in highly concentrated NV-diamonds using photons, phonons, and electrons. These NV-diamonds are synthesized employing a unique nanosecond laser processing technique which results in ultrafast melting and subsequent quenching of nitrogen-doped molten carbon films. Substitutional nitrogen atoms and vacancies are incorporated into diamond during rapid liquid-phase growth, where dopant concentrations can exceed thermodynamic solubility limits through solute trapping. This ultrafast synthesis technique generates fewer surface traps thereby forming similar to 75% NV(- )centers at room-temperature, which are optically and magnetically distinct as compared to NV0 centers. We dramatically increase the NV(- )concentration in NV-diamonds by similar to 53% with decreasing temperature from 300 to 80 K. With negative electrical biasing, the Fermi level in NV-diamond rises and crosses the NV0/- level, thereby promoting an exponential conversion of NV0 to NV(- )centers. We have also photonically enhanced the photoluminescence signal from NV- centers, thereby ascertaining the conversion of NV0 into NV- via absorption of electrons (excited by 532 nm photons) from the valence band in NV-diamond. These NV-centers in diamonds also reveal large excitation lifetime, which ultimately leads to similar to 65% quantum efficiency at room-temperature. With these results, we believe that the precise tuning of charge states in these uniquely prepared highly concentrated NV-diamonds will lead to superior quantum devices. (C) 2018 Elsevier Ltd. All rights reserved.