An field programmable gate array (FPGA)-based device for charge-state readout of nitrogen-vacancy (NV) center in diamond with nanosecond feedback speed

Abstract

Ionization of nitrogen-vacancy (NV) center in diamond from the NV− to NV0 state is a destructive process in applications, where a large amount of time is cost for high-fidelity readout. To this end, real-time adaptive feedback would be helpful to improve the readout efficiency. Here, we develop a field programmable gate array-based device that supports complex calculation and real-time feedback at the nanosecond level. This device integrates a time tagger for photon input, a programmable logic arrays for real-time calculation, and a 20-channel pulse streamer for control output. Based on this device, we demonstrate a high-efficiency of real-time charge-state readout. With this device, the signal-to-noise ratio of maximal adaptive-decision-based charge-state readout can be significantly reduced. Moreover, we demonstrate an application of NV− purification with the real-time feedback, where the contrast of spin-state-dependent fluorescence is improved from 31.7% to 35.0%. The device can be easily extended to other quantum systems.