Abstract: The influence of the non-Markovian, the dipole-dipole interaction of the two atoms and the off-resonant on fidelity of the two identity atoms’ quantum state is studied. The results show that the fidelity of the two identity atoms’ quantum state is relatively higher when the two atoms are initially in the entangled state under the non-Markovian regime, especially in the off-resonant case, in which that the fidelity considerably increases with the interaction of the two atoms. If the two atoms are initially in the separable state, the fidelity of the quantum state is not optimal no matter that the Markovian effect exists or not.

Key words: quantum optics, fidelity of quantum state, full quantum theory, thermal reservoir, non-Markovian effect, dipole-dipole interaction