Spin projection noise and the magnetic sensitivity of optically pumped magnetometers

K. Mouloudakis; V. Koutrouli; I. K. Kominis; M. W. Mitchell; G. Vasilakis

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arXiv · 2402.10746

Spin projection noise and the magnetic sensitivity of optically pumped magnetometers

K. Mouloudakis·V. Koutrouli·I. K. Kominis·M. W. Mitchell·G. Vasilakis

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Abstract

Present protocols for obtaining the ultimate magnetic sensitivity of optically pumped magnetometers (OPMs) utilizing alkali-metal ensembles rely on uncorrelated atoms in stretched states. A new approach for calculating the spin projection noise (SPN)-limited signal to noise ratio (SNR) and the magnetic sensitivity of OPMs is proposed. Our model is based solely on the mean-field density matrix dynamics and in contrast to previous models, it applies to both low and high field regimes, it takes into account the degree of spin polarization, the intra- and interhyperfine correlations, the decoherence processes, the atom-light coupling and the effects of the spin dynamics on the spin-noise spectra. Fine tuning of the probe frequency allow us to explore different hyperfine states and ground-state correlations. Especially in the spin-exchange-relaxation-free (SERF) regime, alongside the magnetic resonance narrowing and the increased number density, hallmarks of SERF magnetometers, we report on a new SERF feature; the reduction of spin-projection noise at the spin precession frequency as a consequence of strongly-correlated hyperfine spins that attenuate and redistribute SPN when properly probed.

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K. Mouloudakis, V. Koutrouli, I. K. Kominis, M. W. Mitchell, G. Vasilakis. 2024-02-22. Spin projection noise and the magnetic sensitivity of optically pumped magnetometers. https://arxiv.org/abs/2402.10746

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