Quantum Discord of two Coupled Qubits with Initial System-reservoir Correlation

Recently, the effect of initial qubit-reservoir correlation for two qubits in a common reservoir on the entanglement dynamics has been studied by Yan and Xia (Acta Sinica Quantum Optica 20, 16 2014 ). We extend their results and investigate how the initial qubit-reservoir correlation and dipole-dipole interaction between two qubits effect on dynamics of quantum discord in Markovian and non-Markovian regimes, respectively. The results show that in general, the larger initial qubit-reservoir correlation and dipole-dipole interaction can retard the decay of quantum discord. Besides, a combination of relatively strong dipole-dipole interaction and non-Markovian effect can efficiently protect quantum discord. Finally,thecomparisonbetweenevolutionsofquantumdiscordandentanglementisalsoconsidered.