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Super Quantum Discord with Weak Measurements
Weak measurements cause small change to quantum states, thereby opening up
the possibility of new ways of manipulating and controlling quantum systems. We
ask, can weak measurements reveal more quantum correlation in a composite
quantum state? We prove that the weak measurement induced quantum discord,
called as the "super quantum discord", is always larger than the quantum
discord captured by the strong measurement. Moreover, we prove the monotonicity
of the super quantum discord as a function of the measurement strength. We find
that unlike the normal quantum discord, for pure entangled states, the super
quantum discord can exceed the quantum entanglement. Our result shows that the
notion of quantum correlation is not only observer dependent but also depends
on how weakly one perturbs the composite system.Comment: Latex, 5 pages, 2 Figs, Monotonicity of the super discord with the
measurement strength is included. Application to the entropic uncertainty
relation will be reported separatel
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