Ultracold atomic gases have revolutionized the study of non-equilibrium dynamics in quantum many-body systems. Many counterintuitive non-equilibrium effects have been observed, such as suppressed thermalization in a one-dimensional (1D) gas, we follow the spatial dynamics of singly, doubly, and triply occupied lattice sites. The system sheds interaction energy by dissolving some doublons and triplons. Some singlons quantum distill out of the doublon center, 6, 7 while others remain confined. 7Our Gutzwiller mean-field model captures these experimental features in a physically clear way. These experiments might be used to study thermalization in systems with particle losses 8 or the evolution of quantum entanglement, 9,10 or if applied to fermions, to prepare very low entropy states.

We study the transverse expansion of arrays of ultracold 87 Rb atoms weakly confined in tubes created by a 2D optical lattice, and observe that transverse expansion is delayed because of mutual atom interactions. A mean-field model of a coupled array shows that atoms become localized within a roughly square fort-like self-trapping barrier with time-evolving edges. But the observed dynamics is poorly described by the meanfield model. Theoretical introduction of random phase fluctuations among tubes improves the agreement with experiment, but does not correctly predict the density at which the atoms start to expand with larger lattice depths. Our results suggest a new type of self-trapping, where quantum correlations suppress tunneling even when there are no density gradients.

We derive a general expression for the spontaneous-emission-induced transition rates between the atomic states of atoms trapped in far-detuned optical potentials, taking into account both their internal and external degrees of freedom. We apply this result to atoms trapped in deep optical lattices. For one-and two-dimensional lattices, we quantify the correlations among excitations in the tightly confined directions, the loosely trapped directions, and the internal state of the atom. We emphasize the differences in excitations between red-and blue-detuned lattices.

We study theoretically how excitations due to spontaneous emission and trap fluctuations combine with elastic collisions to change the momentum distribution of a trapped nondegenerate one-dimensional (1D) Bose gas. Using calculated collisional relaxation rates, we first present a semianalytical model for the momentum distribution evolution to get insight into the main processes responsible for the system dynamics. We then present a Monte Carlo simulation that includes features that cannot be handled analytically and compare its results to experimental data. These calculations provide a baseline for how 1D Bose gases evolve due to heating processes in the absence of diffractive collisions that might thermalize the gases.

We study the loss of atoms in quantum Newton's cradles (QNCs) with a range of average energies and transverse confinements. We find that the three-body collision rate in one-dimension is strongly energy dependent, as predicted by a strictly 1D theory. We adapt the theory to atoms in waveguides, then using detailed momentum measurements to infer all the collisions that occur, we compare the observed loss to the adapted theory and find that they agree well.