  Dissipation is ubiquitous in nature and plays a crucial role in quantum
systems such as causing decoherence of quantum states. Recently, much attention
has been paid to an intriguing possibility of dissipation as an efficient tool
for preparation and manipulation of quantum states. Here we report the
realization of successful demonstration of a novel role of dissipation in a
quantum phase transition using cold atoms. We realize an engineered dissipative
Bose-Hubbard system by introducing a controllable strength of two-body
inelastic collision via photo-association for ultracold bosons in a
three-dimensional optical lattice. In the dynamics subjected to a slow
ramp-down of the optical lattice, we find that strong on-site dissipation
favors the Mott insulating state: the melting of the Mott insulator is delayed
and the growth of the phase coherence is suppressed. The controllability of the
dissipation is highlighted by quenching the dissipation, providing a novel
method for investigating a quantum many-body state and its non-equilibrium
dynamics.
