  The quantum dynamics of a one-dimensional bosonic Josephson junction is
studied by solving the time-dependent many-boson Schr\"odinger equation
numerically exactly. Already for weak interparticle interactions and on short
time scales, the commonly-employed mean-field and many-body methods are found
to deviate substantially from the exact dynamics. The system exhibits rich
many-body dynamics like enhanced tunneling and a novel equilibration phenomenon
of the junction depending on the interaction, attributed to a quick loss of
coherence.
