The dynamics of quantum discord and entanglement of two atoms coupled to two spatially separate cavities in cavity QED

Abstract

In this paper, we study the dynamics of quantum discord and entanglement of two identical two-level atoms A and B coupled with two spatially separate single-mode high-Q cavities a and b in cavity QED, respectively. Making use of geometrical depiction of quantum discord and entanglement of formation (EoF), we show that there exists quantum discord sudden death (DSD) as well as entanglement sudden death (ESD) and the time interval of DSD is shorter than that of ESD in the presented quantum system. In addition, the rate of decreasing of quantum discord is slower than that of entanglement. We have shown that the amount of quantum discord and entanglement and the relative ordering between quantum discord and quantum entanglement depend on the purity p in the presented quantum system. And we have also shown that quantum discord and entanglement of the qubits AB can transfer to the cavities ab and vice versa. Moreover, the transfer of quantum discord is independent of the purity p but that of quantum entanglement is dependent of the purity p. Surprisingly, the sudden changes of quantum discord of qubits and cavities are observed when the initial states of qubits are mixed.