Dynamics of Atom-Atom Correlations in the Fermi problem
  We present a detailed perturbative study of the dynamics of several types of atom-atom correlations in the famous Fermi problem. This is an archetypal model to study micro-causality in the quantum domain where two atoms, the first initially excited and the second prepared in its ground state, interact with the vacuum electromagnetic field. The excitation can be transferred to the second atom via a flying photon and various kinds of quantum correlations between the two are generated during this process. Among these, prominent examples are given by entanglement, quantum discord and nonlocal correlations. It is the aim of this paper to analyze the role of the light cone in the emergence of such correlations. 
Massimo Borrelli, Carlos Sab\'in, Gerardo Adesso, Francesco Plastina,   Sabrina Maniscalco
quant-ph