2014/11/26 by Tim Langen, Sebastian Erne, Remi Geiger +7 · 3 citations
Physics and Astronomy · #cond-mat.quant-gas #cond-mat.stat-mech #quant-ph
paper · pdf · doi:10.1126/science.1257026
published as Science 348 (2015) 207-211 · 5 pages + 4 pages supp. mat., 4 figures
arxiv created 2014/11/26 · arxiv updated 2015/04/14
The connection between the non-equilibrium dynamics of isolated quantum many-body systems and statistical mechanics is a fundamental open question. It is generally believed that the unitary quantum evolution of a sufficiently complex system leads to an apparent maximum-entropy state that can be described by thermodynamical ensembles. However, conventional ensembles fail to describe the large class of systems that exhibit non-trivial conserved quantities. Instead, generalized ensembles have been predicted to maximize entropy in these systems. In our experiments we explicitly show that a degenerate one-dimensional Bose gas relaxes to a state that can be described by such a generalized ensemble. This is verified through a detailed study of correlation functions up to 10th order. The applicability of the generalized ensemble description for isolated quantum many-body systems points to a natural emergence of classical statistical properties from the microscopic unitary quantum evolution.