Experimental Realization of One-Dimensional Bose Gases

Toshiya Kinoshita, Trevor Wenger, David S. Weiss

Vyacheslav I. Yukalov, Marvin D. Girardeau

One-dimensional Bose gases are considered, interacting either through the hard-core potentials or through the contact delta potentials. Interest in these gases gained momentum because of the recent experimental realization of quasi-one-dimensional Bose gases in traps with tightly confined radial motion, achieving the Tonks-Girardeau (TG) regime of strongly interacting atoms. For such gases the Fermi-Bose mapping of wavefunctions is applicable. The aim of the present communication is to give a brief survey of the problem and to demonstrate the generality of this mapping by emphasizing that: (i) It is valid for nonequilibrium wavefunctions, described by the time-dependent Schrödinger equation, not merely for stationary wavefunctions. (ii) It gives the whole spectrum of all excited states, not merely the ground state. (iii) It applies to the Lieb-Liniger gas with the contact interaction, not merely to the TG gas of impenetrable bosons.

William D. Phillips, J. H. Huckans, B. Laburthe-Tolra +4 more

Stefan K. Baur

Rapid progress in the field of ultracold atoms allows the study of many new and old models of quantum many-body physics. In this doctoral dissertation we theoretically explore exotic phases of ultracold quantum gases, with a special focus spin-imbalanced attractive Fermi gases in lower dimensional situations. Chapter 2 reviews the mean-field theory approach to pairing in twocomponent Fermi gases. Applications of this theory are illustrated in Chapter 3, where we discuss mostly well-known results of mean-field theory applied to imbalanced Fermi gases. Adapted from the author's prior publications, Chapters 4, 5 use the theory developed in Chapters 2, 3. In Chapter 6 we discuss the physics of Fermi gases, squeezed into one spatial dimension. In this and Chapter 7, we go beyond mean-field theory, approaching the problem through the Bethe ansatz, exact solutions to few-body problems and Fermi-Bose mappings ("fermionization"). We also show results from a joint effort with the experimental group of Randy Hulet at Rice University to experimentally realize and probe a strongly interacting one dimensional paired Fermi gas. In Chapter 8, after a brief introduction to rapidly rotating two dimensional Bose gases, we introduce a new protocol to create few atom fractional quantum Hall states. Finally, in Chapter 9 we study the effects of two-body losses on lattice Bose gases with hardcore interactions in one and two spatial dimensions.

Tim Langen

Frederik Møller, Thomas Schweigler, Mohammadamin Tajik +4 more

We design a neural network to extract and process features from absorption images taken of one-dimensional Bose gases in the quasicondensate regime. Specifically, the network is trained to predict both the temperature of single realizations of the system and the uncertainty thereof. For multiple realizations, the individual predictions can be combined in an estimate of the mean temperature, improving precision. We benchmark our model on both simulated and experimentally measured data and compare it to the established method of density ripple thermometry. We find the predictions of the two methods compatible, although the neural network reaches similar precision needing many fewer realizations, thus highlighting the efficiency gain achievable when incorporating neural networks into analysis of data from cold gas experiments. Further, we study feature maps to reveal which local features of the condensate are extracted by the network and how said features correlate with properties of the system. A similar analysis could be employed to uncover physical relations in more complex systems.