Non-equilibrium coherence dynamics in one-dimensional Bose gases

Abstract

Low-dimensional systems provide beautiful examples of many-body quantum physics. For one-dimensional (1D) systems, the Luttinger liquid approach provides insight into universal properties. Much is known of the equilibrium state, both in the weakly and strongly interacting regimes. However, it remains a challenge to probe the dynamics by which this equilibrium state is reached. Here we present a direct experimental study of the coherence dynamics in both isolated and coupled degenerate 1D Bose gases. Dynamic splitting is used to create two 1D systems in a phase coherent state. The time evolution of the coherence is revealed through local phase shifts of the subsequently observed interference patterns. Completely isolated 1D Bose gases are observed to exhibit universal sub-exponential coherence decay, in excellent agreement with recent predictions. For two coupled 1D Bose gases, the coherence factor is observed to approach a non-zero equilibrium value, as predicted by a Bogoliubov approach. This coupled-system decay to finite coherence is the matter wave equivalent of phase-locking two lasers by injection. The non-equilibrium dynamics of superfluids has an important role in a wide range of physical systems, such as superconductors, quantum Hall systems, superfluid helium and spin systems. Our experiments studying coherence dynamics show that 1D Bose gases are ideally suited for investigating this class of phenomena.

Non-equilibrium dynamics of an unstable quantum pendulum explored in a spin-1 Bose–Einstein condensate

“…In future work, we intend to further investigate the damping of the spin dynamics and its connection to thermalization of isolated quantum systems subject to loss. Similar investigations are ongoing using one-dimensional condensate systems [30][31][32][33] , and it will be interesting to explore the similarities and differences in these completely different systems.…”

Quantum states and phases in driven open quantum systems with cold atoms

“…Surprisingly, with this definition the jump operator reduces to c ℓ ≡ d ℓ and the master equation (1) in the long wave length limit |q|a < U n/J is mapped to the same form as the master equation in the previous section, with the operator a ℓ replaced by the new operator d ℓ and the chemical potential U n replaced by U n − ǫ ℓ /2. Consequently, we find again the exact solution to the master equation, which allows us to characterize the state via its correlation functions, see Appendix C; such a characterization of a states in cold gases has attracted a lot of interest recently [25,26,27,28].…”

Stationary behaviour of observables after a quantum quench in the spin-1/2 Heisenberg XXZ chain

“…Nonequilibrium dynamics in closed quantum systems, and in particular quantum quenches, have attracted much experimental [1][2][3][4][5][6] and theoretical attention in recent years. There is a growing consensus that integrable models exhibit important differences in behaviour as compared to non-integrable ones 41 .…”