Enhancement of transmission rates in quantum memory channels with damping.

We consider the transfer of quantum information down a single-mode quantum transmission line. Such a quantum channel is modeled as a damped harmonic oscillator, the interaction between the information carriers -a train of N qubits- and the oscillator being of the Jaynes-Cummings kind. Memory effects appear if the state of the oscillator is not reset after each channel use. We show that the setup without resetting is convenient in order to increase the transmission rates, both for the transfer of quantum and classical private information. Our results can be applied to the micromaser.