Sub-Shot-Noise Magnetometry with a Correlated Spin-Relaxation Dominated Alkali-Metal Vapor

TL;DR

This paper demonstrates that spin squeezing can improve magnetometric sensitivity in alkali-metal vapors even with dominant correlated spin relaxation, challenging previous assumptions about decoherence effects.

Contribution

It reveals that spin squeezing remains effective in reducing spin noise under correlated relaxation conditions, extending quantum measurement limits.

Findings

Spin squeezing reduces spin noise despite relaxation.

Correlated spin relaxation can be harnessed to enhance sensitivity.

Long measurement times benefit from spin squeezing in this regime.

Abstract

Spin noise sets fundamental limits to the precision of measurements using spin-polarized atomic vapors, such as performed with sensitive atomic magnetometers. Spin squeezing offers the possibility to extend the measurement precision beyond the standard quantum limit of uncorrelated atoms. Contrary to the current understanding, we show that even in the presence of spin relaxation, spin squeezing can lead to a significant reduction of spin noise, and hence an increase in magnetometric sensitivity, for a long measurement time. This is the case when correlated spin relaxation due to binary alkali-atom collisions dominates independently acting decoherence processes.