arXiv 2303.047872023-03-08quant-ph

Bell参数的单对测量

Single-pair measurement of the Bell parameter

Salvatore Virzì, Enrico Rebufello, Francesco Atzori, Alessio Avella, Fabrizio Piacentini, Rudi Lussana, Iris Cusini, Francesca Madonini, Federica Villa, Marco G… 展开作者

Salvatore Virzì, Enrico Rebufello, Francesco Atzori, Alessio Avella, Fabrizio Piacentini, Rudi Lussana, Iris Cusini, Francesca Madonini, Federica Villa, Marco Gramegna, Eliahu Cohen, Ivo Pietro Degiovanni, Marco Genovese

备注：: 14 pages, 3 figures
发表信息：: Quantum Sci. Technol. 9, 045027 (2024)
DOI：: 10.1088/2058-9565/ad6a37

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AI总结：

首次利用顺序弱测量实现单对Bell不等式测试，为每个纠缠对获取Bell参数值，消除了自由选择漏洞并证明测量后仍保留纠缠。

摘要：

Bell不等式是量子基石之一，也是量子技术的基础工具。最近，全球科学界为此付出了大量努力，最终实现了无漏洞实验。尽管如此，由于波函数坍缩禁止在同一量子态上执行评估整个Bell参数所需的所有测量，迄今为止的实验测试都无法从每个纠缠对中提取完整不等式的信息。我们在此提出首个单对Bell不等式测试，能够为每个探测到的纠缠对获得Bell参数值。这通过利用顺序弱测量实现，允许在每个纠缠粒子的同一状态上依次测量非对易可观测量。这种方法不仅赋予了前所未有的测量能力，还消除了在不同测量基之间选择的需要，从根本上消除了自由选择漏洞，并拓展了反事实确定性的概念（因为它允许在原本未选择的基中进行测量）。我们还演示了在Bell参数测量后，测试对仍呈现出显著的纠缠量，证明了（完全）波函数坍缩的缺失，并允许利用这一量子资源进行后续协议。

英文摘要：

Bell inequalities are one of the cornerstones of quantum foundations, and fundamental tools for quantum technologies. Recently, the scientific community worldwide has put a lot of effort towards them, which culminated with loophole-free experiments. Nonetheless, none of the experimental tests so far was able to extract information on the full inequality from each entangled pair, since the wave function collapse forbids performing, on the same quantum state, all the measurements needed for evaluating the entire Bell parameter. We present here the first single-pair Bell inequality test, able to obtain a Bell parameter value for every entangled pair detected. This is made possible by exploiting sequential weak measurements, allowing to measure non-commuting observables in sequence on the same state, on each entangled particle. Such an approach not only grants unprecedented measurement capability, but also removes the need to choose between different measurement bases, intrinsically eliminating the freedom-of-choice loophole and stretching the concept of counterfactual-definiteness (since it allows measuring in the otherwise not-chosen bases). We also demonstrate how, after the Bell parameter measurement, the pair under test still presents a noteworthy amount of entanglement, providing evidence of the absence of (complete) wave function collapse and allowing to exploit this quantum resource for further protocols.

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