Triple-Tone Microwave Control for Sensitivity Optimization in Compact Ensemble Nitrogen-Vacancy Magnetometers

Ensembles of nitrogen-vacancy (NV) centers in diamond are a well-established platform for quantum magnetometry under ambient conditions. However, the hyperfine structure of the NV for the 14N isotope results in a threefold reduction of contrast and thus sensitivity. By addressing all the hyperfine transitions simultaneously with triple-tone microwave control, this loss can be mitigated. We experimentally and theoretically compare triple-tone and standard single-tone control for two DC magnetometry protocols: pulsed optically detected magnetic resonance (ODMR) and Ramsey interferometry.

We validate a master equation model of the NV dynamics against ensemble NV measurements carried out using a magnetometer from SBQuantum to map sensitivity versus microwave power and dephasing rates. Triple-tone driving enhances pulsed ODMR sensitivity by up to a factor of three in low-dephasing regimes, while for Ramsey interferometry, benefits appear only under power-limited conditions. These results [1] identify practical regimes where triple-tone control can improve the performance in portable and power-limited NV ensemble magnetometers.

[1] A. Chakravarty et al., arXiv:2510.00913 (2025).