Spatial Microwave Field Frequency Measurement through Two‐Level Resonance of Nitrogen‐Vacancy Color Center in Diamonds

This article presents a frequency measurement method for spatial microwave signals with solid‐state atom resonance, performing measurements based on the burnt hole in spectrum with two microwave fields acting on nitrogen vacancies (NVs) simultaneously. The population on |0⟩ of the NV color center in the ground state affected by the resonance of two microwave fields with similar frequencies responds excellently to external microwave frequencies, and a phenomenon named hole burning occurs. The full width at half maximum (FWHM) of the resonant peak at the hole is 18.9 kHz. When microwaves of different frequencies are applied, the resonant peak precisely follows the signal frequency in the experiment. Subsequently, the resonant peak is processed using the differential method to obtain a frequency measurement error on the order of 100 Hz. The spatial resolution of this method is within the millimeter scale. This study can provide technical support for applications in microwave frequency measurement and spatial mapping with quantum precision measurement.