Spin-exchange collisions in hot vapors creating and sustaining bipartite entanglement

In this article, Kostas Mouloudakis, a PhD student of our Department and Iannis Kominis, Associate Professor at our Department, use techniques of quantum information science to quantify the atom-atom correlations produced by spin-exchange collisions in hot alkali vapors. Such vapors form the physical realization of several quantum technologies relevant to quantum sensing, most notably ultrasensitive atomic magnetometers. 

So far, such alkali vapors have been theoretically described as consisting of uncorrelated atoms. It was intuitively expected that an ensemble of atoms undergoing random collisions in a hot vapor cannot sustain quantum correlations for an experimentally meaningful time. 

Recently however, experiments started to hint towards the opposite. In this work, the authors show theoretically that the atom-atom entanglement produced by spin-exchange collisions is strong and long-lived. Furthermore, it can be directly manifested in bipartite spin correlations which determine measurable collective spin variances. 

This work provides new insights into relevant spin-noise measurements performed at the Laboratory for Quantum Physics and Quantum Biology and elsewhere, and has the potential to shed light on novel multi-body quantum dynamics in hot atomic vapors and their use in quantum metrology.

Article: “Spin-exchange collisions in hot vapors creating and sustaining bipartite entanglement”, K. Mouloudakis, I.K. Kominis, Phys. Rev. A 103, L010401 – 6 January 2021