Decoherence effects in interacting qubits under the influence of various environments

We study competition between the dissipative and coherent effects in the entanglement dynamics of two qubits. The coherent interactions are needed for designing logic gate operations with systems such as ion traps, semiconductor quantum dots and atoms. We show that the interactions lead to a phenomenon of periodic disentanglement and entanglement between the qubits. The disentanglement is primarily caused by environmental perturbations. The qubits are seen to remain disentangled for a finite time before getting entangled again. We find that the phenomenon is generic and occurs for a wide variety of models of the environment. We present analytical results for the time dependence of concurrence for all the models. The periodic disentanglement and entanglement behaviour is seen to be a precursor to the sudden death of entanglement (ESD) and can happen for environments which do not show ESD for non-interacting qubits. Further we also find that this phenomenon can even lead to delayed death of entanglement for correlated environments.