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Phys. Rev. Lett. 101, 155303 (2008) [4 pages]

Expansion of a Quantum Gas Released from an Optical Lattice

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F. Gerbier1,*, S. Trotzky2, S. Fölling3, U. Schnorrberger2, J. D. Thompson2, A. Widera4, I. Bloch2, L. Pollet5, M. Troyer5, B. Capogrosso-Sansone6, N. V. Prokof’ev5,6,7, and B. V. Svistunov6,7
1Laboratoire Kastler Brossel, ENS, UPMC, CNRS, 24 rue Lhomond, 75005 Paris, France
2Institut für Physik, Johannes Gutenberg-Universität, 55099 Mainz, Germany
3Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
4Institut für Angewandte Physik, 53115 Bonn, Germany
5Theoretische Physik, ETH Zurich, 8093 Zurich, Switzerland
6Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003, USA
7Russian Research Center “Kurchatov Institute,” 123182 Moscow, Russia

Received 26 July 2008; published 9 October 2008

We analyze the interference pattern produced by ultracold atoms released from an optical lattice, commonly interpreted as the momentum distributions of the trapped quantum gas. We show that for finite times of flight the resulting density distribution can, however, be significantly altered, similar to a near-field diffraction regime in optics. We illustrate our findings with a simple model and realistic quantum Monte Carlo simulations for bosonic atoms and compare the latter to experiments.

© 2008 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.101.155303
DOI:
10.1103/PhysRevLett.101.155303
PACS:
67.85.−d, 03.75.Gg, 03.75.Hh, 05.30.Jp

*fabrice.gerbier@lkb.ens.fr

 
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