  A simple and convenient design enables real-time three-dimensional position
tracking of nitrogen-vacancy (NV) centers in diamond. The system consists
entirely of commercially available components (a single photon counter, a
high-speed digital-to-analog converter, a phase-sensitive detector-based
feedback device, and a piezo stage), eliminating the need for custom
programming or rigorous optimization processes. With a large input range of
counters and trackers combined with the high sensitivity of single-photon
counting, high-speed position tracking (upper bound recovery time of 0.9 s upon
250 nm of step-like positional shift) not only of bright ensembles but also of
low-photon-collection-efficiency single to few NV centers is possible. The
tracking requires position modulation of only 10 nm, which allows simultaneous
position tracking and pulsed measurements in the long term. Therefore, this
tracking system enables measuring a single spin magnetic resonance and Rabi
oscillations at a very high resolution even without photon collection
optimization. The system is widely applicable to various fields related to NV
centers quantum manipulation research such as NV optical trapping, NV tracking
in fluid dynamics, and biological sensing using NV centers inside a biological
cell.
