Absolute magnetometry based on quantum beats in diamond nitrogen-vacancy centers

TL;DR

This paper introduces an absolute magnetometer using quantum beats in diamond nitrogen-vacancy centers, achieving high sensitivity and robustness against temperature and strain variations for low-frequency magnetic field detection.

Contribution

The authors develop a novel quantum-beat-based magnetometry technique that is immune to temperature and strain effects, improving sensitivity and stability over existing methods.

Findings

Photon-shot-noise limited sensitivity of 38 nT/Hz^1/2

Up to 15-fold sensitivity improvement for long measurements

Elimination of strain-induced dephasing in NV ensembles

Abstract

We demonstrate an absolute magnetometer immune to temperature fluctuation and strain inhomogeneity, based on quantum beats in the ground state of nitrogen-vacancy centers in diamond. We apply this technique to measure low-frequency magnetic field noise using a single nitrogen-vacancy center located within 500 nm of the surface of an isotopically-pure (99.99% C12) diamond. The photon-shot-noise limited sensitivity achieves 38 nT/Hz^1/2 for 4.45 s acquisition time, a factor of 2^1/2 better than the implementation which uses only two spin levels. For long acquisition times (>10 s), we realize up to a factor of 15 improvement in magnetic sensitivity, which demonstrates the robustness of our technique against thermal drifts. Applying our technique to nitrogen-vacancy center ensembles, we eliminate dephasing from longitudinal strain inhomogeneity, resulting in a factor of 2.3 improvement in sensitivity.