Intrinsic Decoherence of a Two-Atom System with Dipole--Dipole

We investigate the effect of dipole--dipole interaction on the intrinsic decoherence of a system which consists of two two-level atoms and an optical cavity. The entanglement of the system is calculated by making use of
concurrence. Our results show that the appropriate choice for the coupling constant Ω of dipole--dipole interaction can restrain the intrinsic decoherence of the system. We also find a special phenomenon. No matter what the value of γ is, the concurrence of system slowly increases and cannot exceed 0.71 when Ω=1.