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arXiv 2202.00440quant-ph
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以因果序换取局域性

Trading causal order for locality

Ravi Kunjwal, Ämin Baumeler

备注：
8 pages, 4 figures, Accepted in Physical Review Letters
发表信息：
Phys. Rev. Lett. 131, 120201 (2023)
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AI总结：

该研究从因果视角分析无纠缠的量子非局域性系综（QNLWE），提出利用无确定因果序的局域操作与经典通信（如AF/BW过程）来完全区分SHIFT系综等态，证明了量子非局域性可以以牺牲确定因果序为代价而消失，并探讨了多方推广在密码学和可分量子操作中的价值。

摘要：

量子理论允许存在无纠缠的量子非局域性系综（QNLWE）。这些系综由看似经典的态（它们是完全可区分且无纠缠的）组成，但无法通过局域操作与经典通信（LOCC）来完全区分。在此，我们从因果视角分析QNLWE，并展示如何使用无确定因果序的局域操作与经典通信来完全区分其中一些系综。具体而言，三方通过访问一种不定因果序的实例——AF/BW过程——能够仅凭局域操作完全区分QNLWE系综——SHIFT系综——中的态。因此，这种类型的量子非局域性在以确定因果序为代价的同时得以消失，同时保留了经典通信。我们的结果由此利用了LOCC是三个约束的合取这一事实：局域操作、经典通信和确定因果序。此外，我们展示了AF/BW过程的多方推广如何转化为展现出QNLWE的多比特系综。此类系综在密码学协议以及研究LOCC无法实现的可分量子操作方面具有独立的研究价值。

英文摘要：

Quantum theory admits ensembles of quantum nonlocality without entanglement (QNLWE). These ensembles consist of seemingly classical states (they are perfectly distinguishable and non-entangled) that cannot be perfectly discriminated with local operations and classical communication (LOCC). Here, we analyze QNLWE from a causal perspective, and show how to perfectly discriminate some of these ensembles using local operations and classical communication without definite causal order. Specifically, three parties with access to an instance of indefinite causal order-the AF/BW process-can perfectly discriminate the states in a QNLWE ensemble--the SHIFT ensemble--with local operations. Hence, this type of quantum nonlocality disappears at the expense of definite causal order while retaining classical communication. Our results thereby leverage the fact that LOCC is a conjunction of three constraints: local operations, classical communication, and definite causal order. Moreover, we show how multipartite generalizations of the AF/BW process are transformed into multiqubit ensembles that exhibit QNLWE. Such ensembles are of independent interest for cryptographic protocols and for the study of separable quantum operations unachievable with LOCC.

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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