  We examine the noise-induced transition in a fluctuating bistable potential
of a driven quantum system in thermal equilibrium. Making use of a Wigner
canonical thermal distribution for description of the statistical properties of
the thermal bath, we explore the generic effects of quantization like vacuum
field fluctuation and tunneling in the characteristic stationary probability
distribution functions undergoing transition from unimodal to bimodal nature
and in signal-to-noise ratio characterizing the co-operative effect among the
noise processes and the weak periodic signal.
