Ali Saif M. Hassan, Pramod S. Joag
Quantum discord, as introduced by Olliver and Zurek [Phys. Rev. Lett.
\textbf{88}, 017901 (2001)], is a measure of the discrepancy between quantum
versions of two classically equivalent expressions for mutual information and
is found to be useful in quantification and application of quantum correlations
in mixed states. It is viewed as a key resource present in certain quantum
communication tasks and quantum computational models without containing much
entanglement. An early step toward the quantification of quantum discord in a
quantum state was by Dakic, Vedral, and Brukner [Phys. Rev. Lett. 105,190502
(2010)] who introduced a geometric measure of quantum discord and derived an
explicit formula for any two-qubit state. Recently, Luo and Fu [Phys. Rev. A
\textbf{82}, 034302 (2010)] introduced a generic form of the geometric measure
of quantum discord for a bipartite quantum state. We extend these results and
find generic forms of the geometric measure of quantum discord and total
quantum correlations in a general N-partite quantum state. Further, we obtain
computable exact formulas for the geometric measure of quantum discord and
total quantum correlations in a N-qubit quantum state. The exact formulas for
the $N$-qubit quantum state are experimentally implementable.
View original:
http://arxiv.org/abs/1202.0104
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