  We use the quantum jump approach to study the entanglement dynamics of a
quantum register, which is composed of two or three dipole-dipole coupled
two-level atoms, interacting with a common environment. Our investigation of
entanglement dynamics reflects that the environment has dual actions on the
entanglement of the qubits in the model. While the environment destroys the
entanglement induced by the coherent dipole-dipole interactions, it can produce
stable entanglement between the qubits prepared initially in a separable state.
The analysis shows that it is the entangled decoherence-free states contained
as components in the initial state that contribute to the stable entanglement.
Our study indicates how the environmental noise produces the entanglement and
exposes the interplay of environmental noise and coherent interactions of
qubits on the entanglement.

Quantum Physics