Decoherence dynamics of discord for multipartite quantum systems

Quantum discord is an optimal resource for the measure of classical and non-classical correlations as compared to other related measures. Geometric measure of quantum discord is another measure of quantum correlations. Recently, the geometric quantum discord (GQD) for multipartite states has been introduced by Xu [J. Phys. A: Math. Theor. 45, 405304 (2012)]. Motivated from the recent study [M.-L. Hu, H. Fan, Ann. Phys. 327, 851 (2012)] for the bipartite systems, I have investigated global quantum discord (QD) and geometric quantum discord (GQD) under the influence of external environments for different multipartite states. Werner-GHZ type three-qubit and six-qubit states are considered in inertial and non-inertial settings. The dynamics of QD and GQD is investigated under amplitude damping, phase damping, depolarizing and flipping channels. The vanishing behaviour of quantum discord is seen for higher level of decoherence, i.e. the behaviour is prominent for p > 0.75 in case of three-qubit GHZ states and for p > 0.5 for six qubit GHZ states. This implies that multipartite states are more fragile to decoherence for higher values of N. Surprisingly, a rapid fall and rise of quantum discord occurs in case of phase flip channel at p = 0.5. However, the behaviour is avoidable in case of bit flip channel for the six-qubit GHZ states. On the other hand, depolarizing channel heavily influences the QD and GQD as compared to the amplitude damping channel. It means that the depolarizing channel has the most destructive influence on the discords for multipartite states. It is also seen that the QD and GQD manifest the phenomena of sudden transition and freeze in the presence of flipping noise. From the perspective of accelerated observers, it is seen that effect of environment on QD and GQD is much stronger than that of the acceleration of non-inertial frames. The degradation of QD and GQD happens due to Unruh effect. Furthermore, QD exhibits more robustness than GQD when the multipartite systems are exposed to environment.