  We study the non-equilibrium dynamics of ultracold bosons in an optical
lattice with a time dependent hopping amplitude J(t)=J_0 +\delta J \cos(\omega
t) which takes the system from a superfluid phase near the Mott-superfluid
transition (J= J_0+\delta J) to a Mott phase (J=J_0-\delta J) and back through
a quantum critical point (J=J_c) and demonstrate dynamic freezing of the boson
wavefunction at specific values of \omega. At these values, the wavefunction
overlap F (defect density P=1-F) approaches unity (zero). We provide a
qualitative explanation of the freezing phenomenon, show it's robustness
against quantum fluctuations and the presence of a trap, compute residual
energy and superfluid order parameter for such dynamics, and suggest
experiments to test our theory.
