Universal determination of comagnetometer response to spin couplings

TL;DR

This paper introduces a universal calibration method for comagnetometers that accurately characterizes their frequency-dependent response to various spin perturbations, improving sensitivity predictions for fundamental physics experiments.

Contribution

The authors develop and experimentally validate a general calibration technique that models the comagnetometer's response across frequencies, addressing limitations of zero-frequency calibration.

Findings

Calibration method accurately predicts response over wide frequency range

Zero-frequency calibration can lead to large sensitivity errors

Method enables better control for dark matter detection experiments

Abstract

We propose and demonstrate a general method to calibrate the frequency-dependent response of self-compensating noble-gas-alkali-metal comagnetometers to arbitrary spin perturbations. This includes magnetic and nonmagnetic perturbations like rotations and exotic spin interactions. The method is based on a fit of the magnetic field response to an analytical model. The frequency-dependent response of the comagnetometer to arbitrary spin perturbations can be inferred using the fit parameters. We demonstrate the effectiveness of this method by comparing the inferred rotation response to an experimental measurement of the rotation response. Our results show that experiments relying on zero-frequency calibration of the comagnetometer response can over- or under-estimate the comagnetometer sensitivity by orders of magnitude over a wide frequency range. Moreover, this discrepancy accumulates over time as operational parameters tend to drift during comagnetometer operation. The demonstrated calibration protocol enables accurate prediction and control of comagnetometer sensitivity to, for example, ultralight bosonic dark-matter fields coupling to electron or nuclear spins as well as accurate monitoring and control of the relevant system parameters.