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arXiv quant-ph/0612049quant-ph
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纠缠度量的约束界

Constrained bounds on measures of entanglement

Animesh Datta, Steven T. Flammia, Anil Shaji, Carlton M. Caves

摘要:

从两个积极的,但不完全是积极的映射密度算子构造的纠缠措施被用来作为约束条件放置的纠缠的形成,纠缠,和并发的4 × N混合状态的界限。这些映射是部分转置映射和Breuer [H.-]提出的$Φ$ -映射。P. Breuer,Phys. Rev. Lett. 97,080501(2006)]。从这两个映射构造的基于范数的纠缠度量,分别称为负性和$Φ$ -负性,导致形成纠缠、纠缠和并发的两组界限。我们比较这些界限,并确定4 × N密度算子的一个约束的界限比其他的界限更好。在这个过程中,我们提出了一个新的推导已经知道的界的同时,基于否定性。我们同时使用这两个约束计算三个纠缠度的新界限。我们演示了如何构建这样的双重约束的界限。我们讨论了我们的结果扩展到更高的维度和两个以上的约束的二分态。

英文摘要:

Entanglement measures constructed from two positive, but not completely positive maps on density operators are used as constraints in placing bounds on the entanglement of formation, the tangle, and the concurrence of 4 x N mixed states. The maps are the partial transpose map and the $Φ$-map introduced by Breuer [H.-P. Breuer, Phys. Rev. Lett. 97, 080501 (2006)]. The norm-based entanglement measures constructed from these two maps, called negativity and $Φ$-negativity, respectively, lead to two sets of bounds on the entanglement of formation, the tangle, and the concurrence. We compare these bounds and identify the sets of 4 x N density operators for which the bounds from one constraint are better than the bounds from the other. In the process, we present a new derivation of the already known bound on the concurrence based on the negativity. We compute new bounds on the three measures of entanglement using both the constraints simultaneously. We demonstrate how such doubly constrained bounds can be constructed. We discuss extensions of our results to bipartite states of higher dimensions and with more than two constraints.

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