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Classification of mixed three-qubit states

A. Acin·D. Bruss·M. Lewenstein·A. Sanpera
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Abstract

We introduce a classification of mixed three-qubit states, in which we define the classes of separable, biseparable, W- and GHZ-states. These classes are successively embedded into each other. We show that contrary to pure W-type states, the mixed W-class is not of measure zero. We construct witness operators that detect the class of a mixed state. We discuss the conjecture that all entangled states with positive partial transpose (PPTES) belong to the W-class. Finally, we present a new family of PPTES "edge" states with maximal ranks.

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A. Acin, D. Bruss, M. Lewenstein, A. Sanpera. 2001-03-07. Classification of mixed three-qubit states. https://doi.org/10.1103/physrevlett.87.040401

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