Fig. 5. Quantum sensing with a single qubit in a physically rotating frame.

(A) We examine the phase accumulated over partial rotations by performing a spin-echo experiment for interrogation times τ < 60 μs. Once the final π/2 pulse has projected the NV into the basis state, we wait for the time remaining in the rotation for the NV to return to the preparation/readout region. (B) Unlike the stationary echo signal (gray), we observe nonzero phase accumulation for the rotating NV. The observed fringes originate from the time-varying projection of the magnetic field onto the NV axis due to misalignment from the rotation axis (data points). The observed signal is well described by an 88 ± 29–mG eAC field that is phase-locked to the diamond rotation (fitted line). Error bars are SE in computed fluorescence ratios averaged over three repeated experimental runs of ~10⁶ repetitions.