Two-atom dark states in electromagnetic cavities

The center-of-mass motion of two two-level atoms coupled to a single damped mode of an electromagnetic resonator is investigated. For the case of one atom being initially excited and the cavity mode in the vacuum state, it is shown that the atomic time evolution is dominated by the appearance of dar k states. These states, in which the initial excitation is stored in the in ternal atomic degrees of freedom and the atoms become quantum mechanically entangled, are almost immune against photon loss from the cavity. Various p roperties of the dark states within and beyond the Raman-Nath approximation of atom optics are worked out. [S1050-2937(99)06105-3].