Monogamy equality in 2 circle times 2 circle times d quantum systems

摘要

There is an interesting property about multipartite entanglement, called the monogamy of entanglement. The property can be shown by the monogamy inequality, called the Coffman-Kundu-Wootters inequality [Phys. Rev. A 61, 052306 (2000); Phys. Rev. Lett. 96, 220503 (2006) ], and more explicitly by the monogamy equality in terms of the concurrence and the concurrence of assistance, C-A(BC)(2)=C-AB(2)+(C-AC(a))(2), in the three-qubit system. In this paper, we consider the monogamy equality in 2 circle times 2 circle times d quantum systems. We show that C-A(BC)=C-AB if and only if C-AC(a) =0 and also show that if C-A(BC)=C-AC(a), then C-AB=0, while there exists a state in a 2 circle times 2 circle times d system such that C-AB=0 but C-A(BC)>C-AC(a). (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3020685]