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arXiv:2607.18808

In Situ Coherence Measurements of Scattered Light in Magnetically Trapped Cold Atomic Clouds: Probe-Driven Atomic Dynamics

Amilson R. Fritsch, Hector Letellier, Leonardo Lima da Silva, Pierre Azam, Vanderlei Salvador Bagnato, Robin Kaiser, Mathilde Hugbart

Published Jul 21, 2026• 0 citations
arXivHTMLPDF

Abstract

The use of temporal correlations in scattered photons to probe the microscopic dynamics of ultracold quantum gases has emerged as a powerful, minimally destructive approach for in situ analysis. Here, we demonstrate that temporal coherence spectroscopy can quantitatively characterize atomic motion in a magnetic trap, despite the perturbative effects of the probing light. By measuring the first-order correlation function g (1) ($τ$ ) of light scattered by a 87 Rb cloud confined in a quadrupole trap, we identify radiation-pressure-induced acceleration and heating as the origin of the apparent discrepancy between coherence spectra and temperatures inferred from time-of-flight measurements. A simple dynamical model incorporating these effects restores agreement between theory and experiment, establishing coherence spectroscopy as a reliable in situ probe of velocity distributions in trapped atomic ensembles. Our results pave the way for time-resolved studies of nonequilibrium dynamics and thermalization processes in confined cold gases, complementing conventional destructive imaging techniques.

DOI
10.48550/arxiv.2607.18808

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We have performed precision microwave spectroscopy on ultracold 87Rb{}^{87}\mathrm{Rb}87Rb confined in a magnetic trap, both above and below the Bose-condensation transition. The cold collision frequency shifts for both normal and condensed clouds were measured, which allowed the intrastate and interstate density correlations (characterized by sometimes controversial ``factors of 2'') to be determined. Additionally, temporal coherence of the normal cloud was studied, and the importance of mean-field and velocity-changing collisions in preserving coherence is discussed.
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