Title: Recurrences in an isolated quantum many-body system,
Abstract: Even though the evolution of an isolated quantum system is unitary, the
complexity of interacting many-body systems prevents the observation of
recurrences of quantum states for all but the smallest systems. For large
systems one can not access the full complexity of the quantum states and the
requirements to observe a recurrence in experiments reduces to being close to
the initial state with respect to the employed observable. Selecting an
observable connected to the collective excitations in one-dimensional
superfluids, we demonstrate recurrences of coherence and long range order in an
interacting quantum many-body system containing thousands of particles. This
opens up a new window into the dynamics of large quantum systems even after
they reached a transient thermal-like state.