  We consider a realistic model for the one-atom micromaser consisting of a
cavity maintained in a steady state by the streaming of two-level Rydberg atoms
passing one at a time through it. We show that it is possible to monitor the
robust entanglement generated between two successive experimental atoms passing
through the cavity by the control decoherence parameters. We calculate the
entanglement of formation of the joint two-atom state as a function of the
micromaser pump parameter. We find that this is in direct correspondence with
the difference of the Shannon entropy of the cavity photons before and after
the passage of the atoms for a reasonable range of dissipation parameters. It
is thus possible to demonstrate information transfer between the cavity and the
atoms through this set-up.
