  Normally, quantum fluctuations enhance the escape from metastable states in
the presence of dissipation. Here we show that dissipation can enhance the
stability of a quantum metastable system, consisting of a particle moving in a
strongly asymmetric double well potential, interacting with a thermal bath. We
find that the escape time from the metastable state has a nonmonotonic behavior
versus the system-bath coupling and the temperature, producing a stabilizing
effect.
