In situ control of atom spin in SERF comagnetometer based on dynamic polarization feedback

Abstract

Quantum precision measurements offer superior sensitivity; however, their practical deployment remains constrained by environmental perturbations and quantum decoherence. This study proposes a dynamic polarization feedback technique based on pulsed optical modulation, which enables in-situ stabilization control of electron spin polarization without compromising the self-compensation regime of the spin-exchange relaxation-free (SERF) comagnetometer system. We develop a theoretical model to analyze the electron spin longitudinal polarization response and its dynamic optical absorption measurement in a K-Rb-²¹Ne comagnetometer under modulation scheme, validating high-precision electron spin polarization measurements. By implementing the closed-loop control system, we suppress low-frequency noise by approximately 6.8 dB, achieving a sensitivity of 3.3 × 10⁻⁶ deg/s/Hz^1/2 @1Hz. Long-term system drift is effectively mitigated, and the Allan deviation curve indicates a 12 dB improvement in the bias instability of system, reaching 8.2 × 10⁻³ deg/h @27 s. This work significantly enhances SERF comagnetometer robustness and extends its utility for long-duration measurements of anomalous spin-dependent interactions. Furthermore, it offers broad application potential in quantum spin-based sensors for geophysical exploration, magnetoencephalography and magnetocardiography.