Picotesla fiberized diamond-based AC magnetometer

• Zhang Shaochun, Yong Liu, Long-Kun Shan, Xue-Dong Gao, Jiaqi Geng, Cui Yu, Yang Dong, Xiangdong Chen, Guang-can Guo, and Fang-Wen Sun
• received 02/23/2024; accepted 03/27/2024; posted 03/29/2024; Doc. ID 522062
• Abstract: Portable quantum sensors are crucial for developing practical quantum sensing and metrology applications. Fiberized nitrogen-vacancy (NV) centers in diamonds have emerged as one of the most promising candidates for compact quantum sensors. Nevertheless, due to the difficulty of coherently controlling the ensemble spin and noise suppression in a large volume, it often faces problems such as reduced sensitivity and narrowed bandwidth in integrated lensless applications. Here, we propose a fluorescence signal treatment method for NV spin ensemble manipulation by the exponential fitting of spin polarization processes, instead of integrating the photon emission. This enables spin state readout with a high signal-to-noise ratio and applies to the pulse sensing protocols for large-volume NV spins. Based on this, we further developed a fiberized diamond-based AC magnetometer. With XY8-N dynamical decoupling pulse sequence, we demonstrated a $T_2$-limited sensitivity of 8 pT$\rm{/\sqrt{Hz}}$ and $T_1$-limited frequency resolution of 90 Hz over a wide frequency band from 100 kHz to 3 MHz. This integrated diamond sensor leverages quantum coherence to achieve enhanced sensitivity in detecting AC magnetic fields, making it suitable for implementation in a compact, and portable endoscopic sensor.