Measurements of spin properties of atomic systems in and out of equilibrium via noise spectroscopy

TL;DR

This paper demonstrates how spin noise spectroscopy (SNS) can detect and analyze atomic spin properties both in equilibrium and out of equilibrium, offering high-resolution insights into atomic and magnetic systems.

Contribution

It introduces the application of SNS for nonperturbative probing of spin imbalances and shows its superior resolution over absorption spectroscopy in complex spectral environments.

Findings

SNS accurately measures spin correlations in atomic ensembles.

Controlled optical pumping drives the system out of equilibrium.

SNS outperforms absorption spectroscopy in spectral resolution.

Abstract

We explore the applications of spin noise spectroscopy (SNS) for detection of the spin properties of atomic ensembles in and out of equilibrium. In SNS, a linearly polarized far-detuned probe beam on passing through an ensemble of atomic spins acquires the information of the spin correlations of the system which is extracted using its time-resolved Faraday-rotation noise. We measure various atomic, magnetic and sub-atomic properties as well as perform precision magnetometry using SNS in rubidium atomic vapor in thermal equilibrium. Thereafter, we manipulate the relative spin populations between different ground state hyperfine levels of rubidium by controlled optical pumping which drives the system out of equilibrium. We then apply SNS to probe such spin imbalance nonperturbatively. We further use this driven atomic vapor to demonstrate that SNS can have better resolution than typical absorption spectroscopy in detecting spectral lines in the presence of various spectral broadening mechanisms.