Letter | Published:

Hanbury Brown and Twiss correlations across the Bose–Einstein condensation threshold

Nature Physics volume 8, pages 195198 (2012) | Download Citation

Abstract

Hanbury Brown and Twiss correlations—correlations in far-field intensity fluctuations—yield fundamental information on the quantum statistics of light sources, as demonstrated after the discovery of photon bunching1,2,3. Drawing on the analogy between photons and atoms, similar measurements have been performed for matter-wave sources, probing density fluctuations of expanding ultracold Bose gases4,5,6,7,8. Here we use two-point density correlations to study how coherence is gradually established when crossing the Bose–Einstein condensation threshold. Our experiments reveal a persistent multimode character of the emerging matter-wave as seen in the non-trivial spatial shape of the correlation functions for all probed source geometries, from nearly isotropic to quasi-one-dimensional, and for all probed temperatures. The qualitative features of our observations are captured by ideal Bose gas theory9, whereas the quantitative differences illustrate the role of particle interactions.

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Acknowledgements

We acknowledge support from the Wittgenstein prize, Austrian Science Fund (FWF) projects F40, P21080-N16 and P22590-N16, the European Union projects AQUTE and Marie Curie (FP7 GA no. 236702), the FWF doctoral program CoQuS (W 1210), the EUROQUASAR QuDeGPM Project and the FunMat research alliance. We wish to thank A. Aspect, D. Boiron, A. Gottlieb, I. Mazets, J. Vianna Gomes and C. I. Westbrook for stimulating discussions.

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Affiliations

  1. Vienna Center for Quantum Science and Technology, Atominstitut, TU Wien, 1020 Vienna, Austria

    • A. Perrin
    • , R. Bücker
    • , S. Manz
    • , T. Betz
    • , C. Koller
    • , T. Plisson
    • , T. Schumm
    •  & J. Schmiedmayer
  2. Wolfgang Pauli Institute, 1090 Vienna, Austria

    • A. Perrin
  3. Laboratoire de Physique des Lasers, Université Paris 13, CNRS, 99 Avenue J.-B. Clément, 93430 Villetaneuse, France

    • A. Perrin
  4. Laboratoire Charles Fabry de l’Institut d’Optique, Univ Paris Sud, CNRS, Campus Polytechnique RD128, 91127 Palaiseau, France

    • T. Plisson

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Contributions

A.P., R.B., S.M. and T.S. collected the data presented in this Letter. A.P. analysed the data and developed the ideal Bose gas model. All authors contributed to the building of the experimental set-up, the conceptual formulation of the physics, the interpretation of the data and writing the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to J. Schmiedmayer.

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https://doi.org/10.1038/nphys2212

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