Robust Spin Relaxometry with Fast Adaptive Bayesian Estimation

Spin relaxometry with nitrogen-vacancy (N-$V$) centers in diamond offers a spectrally selective, atomically localized, and calibrated measurement of microwave-frequency magnetic noise, presenting versatile probe for condensed-matter biological systems. Typically, relaxation rates are estimated curve-fitting techniques that do not provide optimal sensitivity, often leading to long acquisition times particularly detrimental systems prone drift or other dynamics interest. Here we show adaptive Bayesian estimation is well suited this problem, producing dynamic pulse sequences rapidly find an operating regime. In many situations (including the system employ), approach can speed by order magnitude. We also present four-signal protocol robust drifts spin readout contrast, polarization, microwave fidelity while still achieving near-optimal sensitivity. The combined technique practical, hardware-agnostic wide range N-$V$ applications.