title: Momentum-Space Correlations of a One-Dimensional Bose Gas.
abstract: Analyzing the noise in the momentum profiles of single realizations of one-dimensional Bose gases, we present the experimental measurement of the full momentum-space density correlations ⟨δn_{p}δn_{p^{'}}⟩, which are related to the two-body momentum correlation function. Our data span the weakly interacting region of the phase diagram, going from the ideal Bose gas regime to the quasicondensate regime. We show experimentally that the bunching phenomenon, which manifests itself as super-Poissonian local fluctuations in momentum space, is present in all regimes. The quasicondensate regime is, however, characterized by the presence of negative correlations between different momenta, in contrast to the Bogolyubov theory for Bose condensates, predicting positive correlations between opposite momenta. Our data are in good agreement with ab initio calculations.
authors.affiliation: Laboratoire Charles Fabry, CNRS UMR 8501, Institut d'Optique, Université Paris Sud 11, 2 Avenue Augustin Fresnel, 91127 Palaiseau, France.
authors.forename: Bess
authors.initials: B
authors.lastname: Fang
authors.affiliation: Laboratoire Charles Fabry, CNRS UMR 8501, Institut d'Optique, Université Paris Sud 11, 2 Avenue Augustin Fresnel, 91127 Palaiseau, France.
authors.forename: Aisling
authors.initials: A
authors.lastname: Johnson
authors.affiliation: Laboratoire de Physique, CNRS UMR 5672, Ecole Normale Supérieure de Lyon, Université de Lyon, 46 Allée d'Italie, Lyon F-69364, France.|Institut Universitaire de France, 103 boulevard Saint-Michel, 75005 Paris, France.
authors.forename: Tommaso
authors.initials: T
authors.lastname: Roscilde
authors.affiliation: Laboratoire Charles Fabry, CNRS UMR 8501, Institut d'Optique, Université Paris Sud 11, 2 Avenue Augustin Fresnel, 91127 Palaiseau, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Bouchoule