Sequential Bayesian experiment design for optically detected magnetic resonance of nitrogen-vacancy centers.

In magnetometry using optically detected magnetic resonance of nitrogen vacancy (NV) centers, we demonstrate more than one order-of-magnitude speed up with sequential Bayesian experiment design as compared with conventional frequency-swept measurements. The NV center is an excellent platform for magnetometry with potential spatial resolution down to few nanometers and demonstrated single-defect sensitivity down to nT/Hz. The NV center is a quantum defect with spin = 1 and coherence time up to several milliseconds at room temperature. Zeeman splitting of the NV energy levels allows detection of the magnetic field via photoluminescence. We compare conventional NV center photoluminescence measurements that use pre-determined sweeps of the microwave frequency with measurements using a Bayesian inference methodology. In sequential Bayesian experiment design, the settings with maximum utility are chosen for each measurement in real time based on the accumulated experimental data. Using this method, we observe an order of magnitude decrease in the NV magnetometry measurement time necessary to achieve a set precision.