  We microscopically model the decoherence dynamics of entangled coherent
states under the influence of vacuum fluctuation. We derive an exact master
equation with time-dependent coefficients reflecting the memory effect of the
environment, by using the Feynman-Vernon influence functional theory in the
coherent-state representation. Under the Markovian approximation, our master
equation recovers the widely used Lindblad equation in quantum optics. We then
investigate the non-Markovian entanglement dynamics of the quantum channel in
terms of the entangled coherent states under noise. Compared with the results
in Markovian limit, it shows that the non-Markovian effect enhances the
disentanglement to the initially entangled coherent state. Our analysis also
shows that the decoherence behaviors of the entangled coherent states depend
sensitively on the symmetrical properties of the entangled coherent states as
well as the interactions between the system and the environment.
