  We study a dephasing channel with memory, described by a Hamiltonian model in
which the system-environment interaction is described by a stochastic process.
We propose a useful way to describe the channel uses correlations. Moreover, we
give a general expression for the coherences decay factors as a function of the
number of channel uses and of the stochastic process power spectrum. We also
study the impact of memory on the three qubit code, showing that correlations
among channel uses affect very little the code performance.
