Abstract
We search for faces of the convex set consisting of all separable states, which are affinely isomorphic to simplices, to get separable states with unique decompositions. In the two-qutrit case, we found that six product vectors spanning a five dimensional space give rise to a face isomorphic to the 5-dimensional simplex with six vertices, under a suitable linear independence assumption. If the partial conjugates of six product vectors also span a 5-dimensional space, then this face is inscribed in the face for PPT states whose boundary shares the fifteen 3-simplices on the boundary of the 5-simplex. The remaining boundary points consist of PPT entangled edge states of rank four. We also show that every edge state of rank four arises in this way. If the partial conjugates of the above six product vectors span a 6-dimensional space then we have a face isomorphic to 5-simplex, whose interior consists of separable states with unique decompositions, but with non-symmetric ranks. We also construct a face isomorphic to the 9-simplex. As applications, we give answers to questions in the literature Chen and Djoković (J Math Phys 54:022201, 2013) and Chen and Djoković (Commun Math Phys 323:241–284, 2013), and construct 3 ⊗ 3PPT states of type (9,5). For the qubit-qudit cases with d ≥ 3, we also show that (d + 1)-dimensional subspaces give rise to faces isomorphic to the d-simplices, in most cases.
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Communicated by M. B. Ruskai
Partially supported by NRFK 2012-0002600 and NRFK 2012-0000939.
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Ha, KC., Kye, SH. Separable States with Unique Decompositions. Commun. Math. Phys. 328, 131–153 (2014). https://doi.org/10.1007/s00220-014-1980-6
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DOI: https://doi.org/10.1007/s00220-014-1980-6