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A quantum Newton's cradle

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TLDR
In this paper, the authors show that a homogeneous 1D Bose gas with point-like collisional interactions is integrable, and that it is possible to construct a system with many degrees of freedom that does not reach thermal equilibrium even after thousands of collisions.
Abstract
It is a fundamental assumption of statistical mechanics that a closed system with many degrees of freedom ergodically samples all equal energy points in phase space. To understand the limits of this assumption, it is important to find and study systems that are not ergodic, and thus do not reach thermal equilibrium. A few complex systems have been proposed that are expected not to thermalize because their dynamics are integrable. Some nearly integrable systems of many particles have been studied numerically, and shown not to ergodically sample phase space. However, there has been no experimental demonstration of such a system with many degrees of freedom that does not approach thermal equilibrium. Here we report the preparation of out-of-equilibrium arrays of trapped one-dimensional (1D) Bose gases, each containing from 40 to 250 87Rb atoms, which do not noticeably equilibrate even after thousands of collisions. Our results are probably explainable by the well-known fact that a homogeneous 1D Bose gas with point-like collisional interactions is integrable. Until now, however, the time evolution of out-of-equilibrium 1D Bose gases has been a theoretically unsettled issue, as practical factors such as harmonic trapping and imperfectly point-like interactions may compromise integrability. The absence of damping in 1D Bose gases may lead to potential applications in force sensing and atom interferometry.

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References
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Journal ArticleDOI

Entropy of isolated quantum systems after a quench.

TL;DR: In this paper, the authors studied the effect of entropy on the integrability of hard core bosons and spinless fermions in a superlattice potential and showed that their diagonal entropy is additive and different from the entropy of a generalized Gibbs ensemble.
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Thermalization near integrability in a dipolar quantum Newton's cradle.

TL;DR: In this paper, the authors studied the dynamics of the momentum distribution function in a dipolar quantum Newton's cradle consisting of highly magnetic dysprosium atoms and provided the first experimental evidence that thermalization close to a strongly interacting integrable point occurs in two steps: prethermalization followed by nearexponential thermalization.
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Many-body quantum chaos: Recent developments and applications to nuclei

TL;DR: In the last decade, there has been an increasing interest in the analysis of energy level spectra and wave functions of nuclei, particles, atoms and other quantum many-body systems by means of statistical methods and random matrix ensembles as mentioned in this paper.
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Interaction quenches in the one-dimensional Bose gas

TL;DR: In this article, it was shown that the divergence of the conserved charges is endemic to any continuum integrable system with contact interactions undergoing a sudden quench, leading to significant deviations from the predictions of the grand canonical ensemble in cold-atom systems.
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Dynamics of a Quantum Phase Transition and Relaxation to a Steady State

TL;DR: In this paper, the authors review recent theoretical work on two closely related issues: excitation of an isolated quantum condensed matter system driven adiabatically across a continuous quantum phase transition or a gapless phase and apparent relaxation of an excited system after a sudden quench of a parameter in its Hamiltonian.