Research on the noise characteristics of a closed-loop 87Rb atom comagnetometer

Abstract

Spin-based comagnetometers have essential applications in studying new physical effects such as the fifth force, Lorentz violations, and spin-gravity interactions. In this paper, a transfer function model of the spin precession phase (frequency) is derived to analyze the comagnetometer's noise mechanism. The theory combined with experiments reveals that the output frequency noise of the spin oscillator above 5 Hz is mainly phase noise from the phase-locked loop. The noise below 5 Hz is mainly from the biased magnetic field noise. When building a comagnetometer using two spin oscillators, the symmetry of the spin oscillator is significant. When the intrinsic physical parameters cannot be symmetrical, the comagnetometer's common-mode suppression capability to magnetic field fluctuations can be enhanced by optimizing the control parameters. In addition, the closed-loop control of Bz can significantly weaken the effect of system asymmetry in the low-frequency band. Finally, when considering the comagnetometer system in nuclear magnetic resonance gyroscopes, a trade-off between the bandwidth and sensitivity can be achieved using theory. This paper is an excellent reference for both the research and application of comagnetometers.