We report non-invasive detection of spin coherence in a collection of Raman-driven cold atoms using dispersive Faraday rotation fluctuation measurements, which opens up new possibilities of probing spin correlations in quantum gases and other similar systems. We demonstrate five orders of magnitude enhancement of the measured signal strength than the traditional spin noise spectroscopy with thermal atoms in equilibrium. Our observations are in good agreement with the comprehensive theoretical modeling of the driven atoms at various temperatures. The extracted spin relaxation rate of cold rubidium atoms with atom number density ∼109/cm3 is of the order of 2π×0.5 kHz at 150 μK, two orders of magnitude less than ∼ 2π×50 kHz of a thermal atomic vapor with atom number density ∼1012/cm3 at 373 K.
@article{arxiv.2104.10473,
title = {Detection of Spin Coherence in Cold Atoms via Faraday Rotation Fluctuations},
author = {Maheswar Swar and Dibyendu Roy and Subhajit Bhar and Sanjukta Roy and Saptarishi Chaudhuri},
journal= {arXiv preprint arXiv:2104.10473},
year = {2021}
}