Picotesla fiberized diamond-based AC magnetometer

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 an XY8-N dynamical decoupling pulse sequence,we demonstrated a T_(2)-limited sensitivity of 8pT/√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.