Entanglement Sudden Death Of Both Two-Level Atoms

Entanglement, as one basic feature distinguishing the quantum world from the classical world, has been important physical resource in quantum computation and quantum information processing. However, quantum system is inevitably affected by environment in practice so that the system is disentangled. Recently, the results of study show that entanglement sudden death may appear in the process of systemic evolution in theory and experiment. Therefore, how to improve entanglement and control entangled states is the most elementary and urgent problem in the study of quantum information.In our paper, we mainly investigate entanglement dynamics of both two-level atoms in cavity quantum electrodynamics and discuss how to weaken entanglement sudden death effect. The main results are following:First, we investigate the influences of dipole-dipole interaction and detuning on the entanglement between two atoms with different initial tripartite entangled W-like states in the Tavis-Cummings model by means of concurrence, respectively. The results show that the entanglement between the two atoms can be enhanced via appropriately tuning the strength of dipole-dipole interaction of two atoms or the detunings between atom and cavity, and the so-called sudden death effect can be weakened simultaneously.Second, we also examine entanglement dynamics between two strongly driven atoms off-resonantly coupled with a single-mode cavity via two-photon process with the help of negativity. The results show that sudden death can appear for two different initial states, but tuning detuning can be used to control entanglement evolution. Furthermore, we also find an atomic decoherence-free subspace so that the initial entanglement between two atoms remains invariable in application.Third, we investigate entanglement dynamics of two atoms with different initial entangled Bell-like states in the coupled-cavity system by means of concurrence. The results show that modulating cavity-cavity hopping strength can increase atomic entanglement and remove sudden death of entanglement.