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We consider two two-level atoms, interacting with two independent dissipative cavities, each of which is driven by an external source. The two cavity fields are both initially prepared in the coherent states, and the two two-level atoms are initially prepared in the singlet state |� i = (|egi | gei)/ p 2. We investigate the influence of the damping constant �, the intensity of the external sources F, and the relative difference of the atomic couplings r on the entanglement between the two atoms. In the dispersive approximation, we find that the entanglement between the two atoms decreases with the time evolution, and the decreasing rate of entanglement depends on the values of F/�, �/!, and r. For the given small values of F/� and �/!, on the one hand, the increasing of r favors entanglement decreasing of the atomic system, on the other hand, when r ! 1 the entanglement decreasing becomes slower. With the increasing of the value of �/!, the influence of r on the decreasing rate of entanglement becomes smaller, and gradually disappears for the big value of �/!.

We propose an experimentally feasible teleportation scheme with three-atom W-class state, which was first proposed by Agrawal and Pati [P. Agrawal and A. Pati, Phys. Rev. A 74 (2006) 062320], in cavity QED. In this scheme atoms interact simultaneously with a nonresonant cavity and there is no energy exchange between the atoms and the cavity. Thus it is insensitive to the cavity decay, which is of importance in view of experiment.

We investigate the influence of the initial mixture of qubits and the dissipation on the entanglement transfer from three-qubit Greenberger–Horne–Zeilinger (GHZ) and W state fields to three matter qubits, which are trapped in three spatially separated cavities. We find that at gt≈11.07, the entanglement transfer can be almost complete no matter what state the qubits are initially prepared in. When the dissipation is taken into account, we find that the spontaneous emission plays the similar role to the cavity damping in the entanglement transfer, and the decay rate of the GHZ state is larger than that of the W state.

Two charge qubits being coupled to a damped cavity with dierent couplings are considered. The dynamical evolution of the entanglement between the two qubits is demonstrated analytically or numerically. It is found that with the cavity dissipation, the steady entanglement between the two qubits can be achieved. The two qubits being initially in the separable and most mixed state can be easily induced to a steady entangled state, and the relative dierence of the couplings can be used to enhance the steady entanglement between the two charge qubits. of the qubits cou- plings on the generation of the entanglement between the two qubits. We adopt the method proposed by Peres (17) and Horodecki (18) in terms of the negative eigenvalues of the partial transposition of the density matrix of the bi- partite system, to measure the degree of the entanglement between the two qubits. We find that in the presence of the cavity dissipation, the steady entanglement between the two qubits can be achieved; and the two qubits can be more easily entangled when they are initially in the most mixed state than in some pure states. We also find that the entanglement between the two charge qubits is maxi- mized for an optimal value of the relative dierence of the qubits couplings, and stronger entanglement between the two charge qubits can be generated by choosing the right strength of the relative dierence

The entanglement of two atomic qubits, which are coupled to a coherent state field with different couplings, is studied. The dynamical evolution of the concurrence, which measures the degree of the entanglement between the two qubits, is plotted versus the scaled time gt. It is found that the two qubits can be entangled by the coherent state field even when they are initially prepared in the most mixed state, and for very weak field, the most mixed state can be more easily entangled than some pure states. It is also found that the entanglement between the qubits sensitively depends on the relative difference of the atomic couplings and the mean photon number of the field.