  We report on a complex zero-temperature decay channel of a classical object
in a metastable state coupled to a quantum degree of freedom. This setting can
be realized in a dc-SQUID where both Josephson-junctions have identical
critical currents I_c but feature strongly asymmetric dynamical parameters;
more precisely, selecting both parameters C and 1/R adequately large for one
and small for the other junction makes the first junction behave essentially
classical but lets quantum effects be present for the second one. The decay
process is initiated by the tunneling of the quantum junction, which distorts
the trapping potential of the classical junction; the metastable state of the
latter then becomes unstable if the distortion is large enough. We present the
dynamical phase diagram of this system providing the dependence of this decay
channel on the external bias current I and on the coupling strength between the
two junctions, determined by the loop inductance L.
