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Phys. Rev. A 69, 020301(R) (2004) [4 pages]

Binegativity and geometry of entangled states in two qubits

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Satoshi Ishizaka*
PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho Kawaguchi, Saitama, Japan
Fundamental Research Laboratories, NEC Corporation, 34 Miyukigaoka, Tsukuba, Ibaraki, Japan

Received 10 August 2003; revised 11 November 2003; published 17 February 2004

We prove that the binegativity is always positive for any two-qubit state. As a result, and as suggested by previous work, the asymptotic relative entropy of entanglement in two qubits does not exceed the Rains bound, and the positive partial transposed-entanglement cost for any two-qubit state is determined to be the logarithmic negativity of the state. Further, the proof reveals some geometrical characteristics of the entangled states, and shows that partial transposition can give another separable approximation of the entangled state in two qubits.

© 2004 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevA.69.020301
DOI:
10.1103/PhysRevA.69.020301
PACS:
03.67.-a, 03.65.Ud

*Electronic mail: isizaka@frl.cl.nec.co.jp