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Local transformation of mixed states of two qubits to Bell diagonal states

Li-Xiang Cen·Nan-Jian Wu·Fu-Hua Yang·Jun-Hong An
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Abstract

The optimal entanglement manipulation for a single copy of mixed states of two qubits is to transform it to a Bell diagonal state. In this paper we derive an explicit form of the local operation that can realize such a transformation. The result obtained is universal for arbitrary entangled two-qubit states and it discloses that the corresponding local filter is not unique for density matrices with rank $n=2$ and can be exclusively determined for that with $n=3$ and 4. As illustrations, a four-parameters family of mixed states are explored, the local filter as well as the transformation probability are given explicitly, which verify the validity of the general result.

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Li-Xiang Cen, Nan-Jian Wu, Fu-Hua Yang, Jun-Hong An. 2002-03-19. Local transformation of mixed states of two qubits to Bell diagonal states. https://doi.org/10.1103/physreva.65.052318

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