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arXiv quant-ph/0212020quant-ph
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对称性下极值局部正算子值测度的构造

Construction of extremal local positive operator-valued measures under symmetry

S. Virmani, M. B. Plenio

摘要:

当我们只需要忠实地再现所有初始状态的测量结果的统计数据时,我们研究了POVM的本地实现。我们首先证明,任何POVM与可分离的元素可以实现一个可分离的超级运营商,并开发技术计算POVM的极值点下的某一类约束,其中包括可分性和PPT性。作为例子,我们考虑的测量是不变的各种对称群(沃纳,各向同性,贝尔对角,本地正交),并证明,在这些情况下的POVM元素的可分性是等价的,通过LOCC的可实现性。我们还计算了极值的这些类的测量下,我们考虑的群体,并给出明确的LOCC协议实现它们。因此,这些协议是本地区分这些对称性的状态的最佳方法。许多有趣的结果之一是,局部区分贝尔对角混合态的最佳方法是使用局部冯诺依曼投影执行2-结果POVM。这是真实的,无论成本函数,被歧视的状态的数量,或先验概率。我们的研究结果给出了本地混合状态歧视,可以定量分析的第一个案例,并可能有应用程序的其他问题,如演示的非本地性,实验纠缠证人,甚至纠缠蒸馏。

英文摘要:

We study the local implementation of POVMs when we require only the faithful reproduction of the statistics of the measurement outcomes for all initial states. We first demonstrate that any POVM with separable elements can be implemented by a separable super-operator, and develop techniques for calculating the extreme points of POVMs under a certain class of constraint that includes separability and PPT-ness. As examples we consider measurements that are invariant under various symmetry groups (Werner, Isotropic, Bell-diagonal, Local Orthogonal), and demonstrate that in these cases separability of the POVM elements is equivalent to implementability via LOCC. We also calculate the extrema of these classes of measurement under the groups that we consider, and give explicit LOCC protocols for attaining them. These protocols are hence optimal methods for locally discriminating between states of these symmetries. One of many interesting consequences is that the best way to locally discriminate Bell diagonal mixed states is to perform a 2-outcome POVM using local von Neumann projections. This is true regardless of the cost function, the number of states being discriminated, or the prior probabilities. Our results give the first cases of local mixed state discrimination that can be analysed quantitatively in full, and may have application to other problems such as demonstrations of non-locality, experimental entanglement witnesses, and perhaps even entanglement distillation.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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