Diagonal quantum discord
Author(s)Liu, Zi-Wen; Takagi, Ryuji; Lloyd, Seth
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Quantum discord measures quantum correlation by comparing the quantum mutual information with the maximal amount of mutual information accessible to a quantum measurement. This paper analyzes the properties of diagonal discord, a simplified version of discord that compares quantum mutual information with the mutual information revealed by a measurement that correspond to the eigenstates of the local density matrices. In contrast to the optimized discord, diagonal discord is easily computable; it also finds connections to thermodynamics and resource theory. Here we further show that, for the generic case of non-degenerate local density matrices, diagonal discord exhibits desirable properties as a preferable discord measure. We employ the theory of resource destroying maps (Liu Z-W et al 2017 Phys. Rev. Lett. 118 060502) to prove that diagonal discord is monotonically nonincreasing under the operation of local discord nongenerating qudit channels, d > 2, and provide numerical evidence that such monotonicity holds for qubit channels as well. We also show that it is continuous, and derive a Fannes-like continuity bound. Our results hold for a variety of simple discord measures generalized from diagonal discord. ©2019 IOP Publishing Ltd.
DepartmentMassachusetts Institute of Technology. Center for Theoretical Physics; Massachusetts Institute of Technology. Research Laboratory of Electronics; Massachusetts Institute of Technology. Department of Physics; Massachusetts Institute of Technology. Department of Mechanical Engineering
Journal of Physics A: Mathematical and Theoretical
Liu, Zi-Wen et al., "Diagonal quantum discord." Journal of Physics A: Mathematical and Theoretical 52, 13 (March 2019): no. 135301 doi. 10.1088/1751-8121/ab0774 ©2019 Authors
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