  The time evolution of a maximally entangled bipartite systems is presented in
this paper. The distillability criterion is given in terms of Kraus operators.
Using the criterion, we discuss the distillability of $2\times 2$ and $n\times
n (n>2)$ systems in their evolution process. There are two distinguished
processes, dissipation and decoherence, which may destroy the distillability.
We discuss the effects of those processes on distillability in details.

Quantum Physics