  We study the non-equilibrium evolution of the phase coherence of a
Bose-Einstein condensate (BEC) in a one dimensional optical lattice, as the
lattice is suddenly quenched from an insulating to a superfluid state. We
observe slowly damped phase coherence oscillations in the regime of large
filling factor (~100 bosons per site) at a frequency proportional to the
generalized Josephson frequency. The truncated Wigner approximation (TWA)
predicts the frequency of the observed oscillations.
