  In this paper, we provide a mechanism of decoherence suppression for open
quantum systems in general, and that for "Schrodinger cat-like" state in
particular, through the strong couplings to non-Markovian reservoirs. Different
from the usual strategies of suppressing decoherence by decoupling the system
from the environment in the literatures, here the decoherence suppression
employs the strong back-reaction from non-Markovian reservoirs. The mechanism
relies on the existence of the singularities (bound states) of the
nonequilibrium retarded Green function which completely determines the
dissipation and decoherence dynamics of open systems. As an application, we
examine the decoherence dynamics of a photonic crystal nanocavity that is
coupled to a waveguide. The strong non-Markovian suppression of decoherence for
the optical cat state is attained.
