Tangles of superpositions and the convex-roof extension

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dc.creatorOsterloh, Andreas
dc.creatorSiewert, Jens
dc.creatorUhlmann, Armin
dc.date2007-10-31
dc.date.accessioned2026-07-07T12:24:02Z
dc.date.available2026-07-07T12:24:02Z
dc.descriptionWe discuss aspects of the convex-roof extension of multipartite entanglement measures, that is, $SL(2,\CC)$ invariant tangles. We highlight two key concepts that contain valuable information about the tangle of a density matrix: the {\em zero-polytope} is a convex set of density matrices with vanishing tangle whereas the {\em convex characteristic curve} readily provides a non-trivial lower bound for the convex roof and serves as a tool for constructing the convex roof outside the zero-polytope. Both concepts are derived from the tangle for superpositions of the eigenstates of the density matrix. We illustrate their application by considering examples of density matrices for two-qubit and three-qubit states of rank 2, thereby pointing out both the power and the limitations of the concepts.
dc.description7 pages, 5 figures, revtex4
dc.identifierhttps://arxiv.org/abs/0710.5909
dc.identifierhttp://arxiv.org/abs/0710.5909
dc.identifierPhys. Rev. A 77, 032310 (2008)
dc.identifierdoi:10.1103/PhysRevA.77.032310
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/214196
dc.subjectQuantum Physics
dc.subjectOther Condensed Matter
dc.titleTangles of superpositions and the convex-roof extension
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