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Super quantum discord for two-qubit X-type states
Tao Li, Teng Ma, Yao-Kun Wang, Shao-Ming Fei and Zhi-Xi Wang
Weak measurement is a new way to manipulate and control quantum systems. Different from projection measurement, weak measurement only makes a small change in status. Applying weak measurement to quantum discord, Singh and Pati proposed a new kind of quantum correlations called "super quantum discord (SQD)" [Annals of Physics 343,141(2014)]. Unfortunately, the super quantum discord is also difficult to calculate. There are only few explicit formulae about SQD. We derive the analytical formulae of SQD for general X-type two-qubit states, which surpass the conclusion for Wenner states and Bell-diagonal states. Furthermore, our results reveal more knowledge about the new insight of quantum correlation and give a new way to compare SQD with normal quantum discord. Finally, we analyze its dynamics under nondissipative channels.