Quantum violation of an instrumental test
Quantum violation of an instrumental test
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DOI：
10.1038/s41567-017-0008-5
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发表时间：
2018-03-01
期刊：
影响因子：
19.6
通讯作者：
Sciarrino, Fabio
中科院分区：
文献类型：
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作者：
Chaves, Rafael;Carvacho, Gonzalo;Sciarrino, Fabio
从实验观察中推断因果关系在科学上是极其重要的。仪器测试为实现这一目标提供了必要的工具，因为它们允许人们即使在存在未观察到的共同原因的情况下也能估计因果相关性。鉴于贝尔定理意味着量子力学与我们对因果关系的最基本概念不相容，理解在经典背景下获得的聚合因果工具是否以及如何能够带到量子领域是至关重要的。在这里，我们展示了在工具场景中，量子效应意味着截然不同的预测。在其他结果中，我们表明，纠缠量子态可以违反仪器测试。此外，我们使用具有主动信息前馈的光子装置演示了这种破坏，从而为这种新形式的非经典行为提供了实验证明。我们的发现在因果推论中具有基本意义，也可能导致量子技术的新应用。
Inferring causal relations from experimental observations is of primal importance in science. Instrumental tests provide an essential tool for that aim, as they allow one to estimate causal dependencies even in the presence of unobserved common causes. In view of Bell's theorem, which implies that quantum mechanics is incompatible with our most basic notions of causality, it is of utmost importance to understand whether and how paradigmatic causal tools obtained in a classical setting can be carried over to the quantum realm. Here we show that quantum effects imply radically different predictions in the instrumental scenario. Among other results, we show that an instrumental test can be violated by entangled quantum states. Furthermore, we demonstrate such violation using a photonic set-up with active feed-forward of information, thus providing an experimental proof of this new form of non-classical behaviour. Our findings have fundamental implications in causal inference and may also lead to new applications of quantum technologies.