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arXiv:1908.05194 · Physical Review Research

Quantum trajectories in spin-exchange collisions reveal the nature of spin-noise correlations in multispecies alkali-metal vapors

K. Mouloudakis, Michail Loulakis, I. K. Kominis

Published Oct 10, 2019• 12 citations
arXivHTMLPDF

Abstract

This paper presents a single-atom model of spin-exchange collisions in hot atomic vapors consistent with its long-standing ensemble description. The authors show how spin-noise can be produced by single-atom quantum trajectories, which are then used to resolve the problem of spin-noise spectroscopy of dual-species vapors.
DOI
10.1103/physrevresearch.1.033017

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The authors perform spin-noise spectroscopy on an unpolarized 87{}^{87}87Rb vapor in the spin-exchange-relaxation-free regime and observe noise spectral distributions that deviate strongly from Lorentzian models that accurately describe lower-density regimes. This observation shows that new kinds of information can be extracted from noise spectra and may improve atomic vapor sensors.
Spin-exchange collisions in alkali or alkali-noble gas vapors are at the basis of quantum sensing, nucleon structure studies, tests of fundamental symmetries, and medical imaging. We here show that spin-exchange collisions in hot alkali vapors naturally produce strong bipartite entanglement, which we explicitly quantify using the tools of quantum information science. This entanglement is shown to have a lifetime at least as long as the spin-exchange relaxation time, and to directly affect measurable spin noise observables. This is a formal theoretical demonstration that a hot and dense atomic vapor dominated by random spin-exchange collisions can support long-lived bipartite and possibly higher-order entanglement.
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