Quantum correlation and entanglement between an ionizing system and a   neighbor atom interacting directly and via a quantized field
  Quantum correlations between two neighbor 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 neighbor atom. Also a measure of entanglement of two atoms can be applied after reduction of the continuum to two levels. 
Vlasta Pe\v{r}inov\'a and Anton\'in Luk\v{s} and Jarom\'ir   K\v{r}epelka and Jan Pe\v{r}ina Jr
quant-ph