  We examine the possibility that a metastable quantum state could experiment a
phenomenon similar to thermal activation but at zero temperature. In order to
do that we study the real-time dynamics of the reduced Wigner function in a
simple open quantum system: an anharmonic oscillator with a cubic potential
linearly interacting with an environment of harmonic oscillators. Our results
suggest that this activation-like phenomenon exists indeed as a consequence of
the fluctuations induced by the environment and that its associated decay rate
is comparable to the tunneling rate as computed by the instanton method, at
least for the particular potential of the system and the distribution of
frequencies for the environment considered in this paper. However, we are not
able to properly deal with the term which leads to tunneling in closed quantum
systems, and a definite conclusion cannot be reached until tunneling and
activation-like effects are considered simultaneously.
