Optical readout of coherent nuclear spins in diamond coupled to electronic spins in a thermal state
Phys. Rev. Applied 24, 064059 – Published 23 December, 2025
DOI: https://doi.org/10.1103/76pr-366b
Abstract
Nuclear spins associated with the nitrogen-vacancy (NV) center are useful resources for quantum information processing and quantum sensing, especially as quantum memories. They are also an emerging platform for constructing inertial sensors. The native nitrogen spin of the NV center can serve as a gyroscope using Ramsey interferometry protocols. The sensitivities of these nuclear-spin-based NV gyroscopes are limited by the phase coherence time of the nuclear spin, which is in turn limited by the longitudinal coherence time of the NV center’s electron spin. There is an active research effort to decouple the nuclear spin from the electron spin and other sources of decoherence to extend the phase coherence time past the NV center electron . However, this presents an associated challenge—how to read out the nuclear spin ensemble if the electronic spins have relaxed into a thermal state. We introduce an optical repump pulse to repolarize electron spins from an artificial thermal state and investigate the effect on the readout of nuclear spins in this regime. We find that for ensemble-based sensors our readout protocol has around a sixfold improvement in sensitivity around the excited-state level anticrossing (ESLAC) at 500 G compared to low fields (200 G), despite the presence of deleterious spin flip-flop dynamics in the excited state. Our results highlight how ESLAC dynamics can benefit inertial sensing and other sensing applications involving nuclear quantum memories.
