Highly Accurate Measurement of Multi-microwave Signal Frequency Based on Diamond NV Centers

This chapter introduces a cutting-edge methodology for measuring multiple microwave signals with exceptional precision using diamond nitrogen-vacancy (NV) centers. The core innovation lies in combining continuous heterodyne techniques with fast Fourier transform (FFT) processing to transform time-domain fluorescence signals into frequency-domain representations, enabling accurate extraction of microwave frequencies. The chapter begins by outlining the limitations of traditional microwave frequency measurement approaches—such as Rydberg atomic vapor cells, SQUIDs, and microwave photonic systems—highlighting their constraints in bandwidth, resolution, and operational conditions. It then delves into the principles of NV centers, explaining how their unique spin-triplet characteristics and fluorescence properties allow for sensitive microwave detection under ambient temperatures. The experimental setup is detailed, including the use of a 532 nm laser for excitation, a single-crystal diamond specimen, and an avalanche photodiode for fluorescence detection, all mounted on a vibration-isolated optical platform. The chapter presents experimental results demonstrating the system’s capability to resolve single and dual microwave signals with a minimum frequency difference of 0.01 Hz, showcasing its high resolution and broadband detection capabilities. The technique’s potential applications in wireless communications, quantum systems, and radiofrequency spectrum analysis are discussed, emphasizing its advantages over existing methods in terms of precision, environmental robustness, and multi-signal detection. Readers will gain insights into a transformative approach that addresses critical gaps in microwave frequency measurement, offering new possibilities for high-precision characterization in emerging technological domains.