Questions tagged [quantum-discord]

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What does a quantum mutual information larger than its classical upper bound represent?

Let $\rho$ be a bipartite state. Its quantum mutual information is defined as $$\newcommand{\tr}{\operatorname{tr}}I(\rho) = S(\tr_B(\rho)) + S(\tr_A(\rho)) - S(\rho),$$ where $S(\sigma)$ is the von ...
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Why is the quantum discord of $\rho$ zero iff $\rho=\sum_j p_j \pi_j\otimes \rho_j$ for mutually orthogonal projections $\pi_j$?

In (Wiseman 2012), the author mentions (equation (4), page 6), that a state $\rho$ has zero quantum discord (more precisely, zero Alice-discord) if and only if it can be written in the form $$\rho = \...
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Quantum discord of a tripartite system A:BC

I know that the quantum discord of a bipartite system can be determined as: $${D_A}({\rho _{AB}}) = I({\rho _{AB}}) - {J_A}({\rho _{AB}}),$$ The subscript of $A$ denotes that the measurement has been ...