quantum thermalization with a magnetic quantum Newton’s cradle
Kolmogorov-Arnold-Moser (KAM) theory is a crowning achievement of
Newtonian mechanics. It accounts for the persistence of regular,
non-chaotic dynamics even in models that are not integrable---e.g.,
the solar system---and captures the onset of chaos as
the dynamics are tuned further from integrability. Thermalization
of near-integrable quantum systems is, however, an unresolved
question, which we explore using a dipolar quantum Newton's cradle.
The magnetic dipole-dipole interaction provides tunability of both an
integrability-breaking perturbation and the nature of the
integrable dynamics. We find that the momentum distribution has two
evolution regimes: fast dephasing followed by near-exponential
thermalization. The work sheds light on the mechanisms by which isolated
quantum many-body systems thermalize and on the temporal structure of the
onset of thermalization.