A Sub-10 pT·Hz ^–1/2 Diamond Quantum Sensor with 1/ <i>f</i> Noise Suppression Using 561 nm Laser Excitation

The nitrogen–vacancy center in diamond enables highly sensitive magnetic-field measurements. In this work, we demonstrate an excellent sensitivity of 7.9 pT·Hz–1/2 in the near-DC range of 1 to 1000 Hz. This performance is achieved using a 35 mW laser power and 1 mW microwave power enabled by 561 nm laser excitation and the resonant-antenna design. By leveraging dual resonance with intrinsic π shift for real-time common-mode rejection, this technique effectively suppresses low-frequency noise and pushes the 1/f corner frequency down to 1 Hz, with a measured sensitivity at 1 Hz of 10.6 pT·Hz–1/2. The magnetometer also exhibits excellent capability in detecting magnetic anomalies, promoting the practical use of diamond quantum sensors in biomedical, geophysical, and other real-world applications.