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Entanglement for rank-2 mixed states

Tobias J. Osborne
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Abstract

In a recent paper, Rungta et. al. [Phys. Rev. A, 64, 042315, 2001] introduced a measure of mixed-state entanglement called the I-concurrence for arbitrary pairs of qudits. We find an exact formula for an entanglement measure closely related to the I-concurrence, the I-tangle, for all mixed states of two qudits having no more than two nonzero eigenvalues. We use this formula to provide a tight upper bound for the entanglement of formation for rank-2 mixed states of a qubit and a qudit.

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Tobias J. Osborne. 2002-03-18. Entanglement for rank-2 mixed states. https://doi.org/10.1103/physreva.72.022309

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