Instituto de Ciencias Matemáticas, 28049, Madrid, Spain.
Escuela Técnica Superior de Ingeniería de Sistemas Informáticos, Universidad Politécnica de Madrid, 28031, Madrid, Spain.
Nat Commun. 2021 Dec 2;12(1):7021. doi: 10.1038/s41467-021-27134-6.
Is the world quantum? An active research line in quantum foundations is devoted to exploring what constraints can rule out the postquantum theories that are consistent with experimentally observed results. We explore this question in the context of epistemics, and ask whether agreement between observers can serve as a physical principle that must hold for any theory of the world. Aumann's seminal Agreement Theorem states that two observers (of classical systems) cannot agree to disagree. We propose an extension of this theorem to no-signaling settings. In particular, we establish an Agreement Theorem for observers of quantum systems, while we construct examples of (postquantum) no-signaling boxes where observers can agree to disagree. The PR box is an extremal instance of this phenomenon. These results make it plausible that agreement between observers might be a physical principle, while they also establish links between the fields of epistemics and quantum information that seem worthy of further exploration.
世界是量子的吗？量子基础研究的一个活跃领域致力于探索哪些约束可以排除与实验观测结果一致的后量子理论。我们在认识论的背景下探讨这个问题，并询问观察者之间的一致性是否可以作为任何世界理论都必须遵守的物理原理。奥曼的开创性共识定理指出，两个观察者（经典系统）不能同意不同意。我们提出了对这个定理的扩展，使其适用于无信号设置。具体来说，我们为量子系统的观察者建立了一个共识定理，同时我们构建了一些（后量子）无信号盒子的例子，其中观察者可以同意不同意。PR 盒子是这种现象的极端实例。这些结果表明，观察者之间的一致性可能是一个物理原理，同时也在认识论和量子信息领域之间建立了联系，这些联系似乎值得进一步探索。
