Strong correlations in light propagation in cold atomic ensembles beyond the mean-field theory of standard optics

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• Janne Ruostekoski (Southampton)
• Friday 08 May 2015, 13:30-15:00
• Physics East 217.

If you have a question about this talk, please contact Vincent Boyer.

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We will present an exact large scale computational solution to light propagation in a dense atomic medium. This is achieved in a cold (laser-cooled), stationary or slowly-moving atomic ensemble in a weak light intensity limit. We compare the numerical solution with the predictions obtained from the standard electrodynamics of a polarizable medium (EDPM) and find that the more than a century-old wisdom of conventional optics simply fails. In the simple studied case the exact solution is obtained by purely classical microscopic electrodynamics. Quantum effects therefore cannot explain away the discrepancies between the exact solution and the predictions of EDPM , but the failure of EDPM reflects cooperative phenomena and strong light-induced correlations between the atoms. The failure can be identified even at surprisingly low atom densities and cooperative deviations may therefore already play role in cold atom systems used in metrology and atom-light interfaces in quantum information processing. The breakdown of standard optics becomes especially dramatic when the average interatomic separation is reduced to around 1/k, where k denotes the resonance wavenumber of light. In particular, we find that there is no overt Lorentz-Lorenz local field shift of the resonance, nor a collective Lamb shift. However, the addition of inhomogeneous broadening that mimics thermal motion of a hot atom vapour restores the usual mean-field phenomenology and the standard results of EDPM . Finally, I will address the results of recent experiments at Institut d’Optique at Paris.

This talk is part of the Cold Atoms series.

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