Quantum correlation and entanglement between an ionizing system and a neighboring atom interacting directly and via a quantized field

Quantum correlations between two neighboring atoms are studied. It is assumed that one atomic system comprises a single auto-ionizing level and the other atom does not contain any auto-ionizing level. The excitation of both atoms is achieved by the interaction with the same mode of the quantized field. It is shown that the long-time behavior of two atoms exhibits quantum correlations even when the atoms do not interact directly. This can be shown using the optical excitation of the neighboring atom. Also a measure of entanglement of two atoms can be applied after reduction of the continuum to two levels.