Entanglement properties of two coupled atoms in Kerr medium

We have investigated the entanglement time evolution of two coupled two-level atoms in Kerr medium. Entanglement of the system is calculated by making use of concurrence. The influences of initial state, Kerr medium, and dipole-dipole coupling intensity between two atoms on the entanglement degree of the two atoms are revealed. Results show that the appropriate choice for the nonlinear coupling constant of Kerr medium and the dipole-dipole coupling intensity can improve the degree of atom-atom entanglement and eliminate the entanglement sudden death completely. We also find that invariant and stable entanglement occurs for a particular initial state.