Developing robust microwave-field sensors is both fundamentally and practically important with a wide range of applications from astronomy to communication engineering. The Nitrogen-Vacancy (NV) center in diamond is an attractive candidate for such purpose because of its magnetometric sensitivity, stability and compatibility with ambient conditions. However, the existing NV center-based magnetometers have limited sensitivity in the microwave band. Here we present a continuous heterodyne detection method that can enhance the sensor's response to weak microwaves, even in the absence of spin controls. Experimentally, we achieve a sensitivity of 8.9 pT⋅Hz−1/2 for microwaves of 2.9 GHz by simultaneously using an ensemble of nNV∼2.8×1013 NV centers within a sensor volume of 4×10−2 mm3. Besides, we also achieve 1/t scaling of frequency resolution up to measurement time t of 10000 s. Our method removes the control pulses and thus will greatly benefit the practical application of diamond-based microwave sensors.
@article{arxiv.2206.08533,
title = {Picotesla magnetometry of microwave fields with diamond sensors},
author = {Zhecheng Wang and Fei Kong and Pengju Zhao and Zhehuang Huang and Pei Yu and Ya Wang and Fazhan Shi and Jiangfeng Du},
journal= {arXiv preprint arXiv:2206.08533},
year = {2022}
}