Observers of quantum systems cannot agree to disagree



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Contreras Tejada, Patricia and Scarpa, Giannicola and Kubicki, Aleksander M. and Brandenburger, Adam and La Mura, Pierfrancesco (2021) Observers of quantum systems cannot agree to disagree. Nature Communications, 12 (1). ISSN 2041-1723

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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.

Item Type:Article
Uncontrolled Keywords:Quantum information; Theoretical physics
Subjects:Sciences > Physics > Quantum theory
ID Code:74369
Deposited On:06 Sep 2022 16:01
Last Modified:07 Sep 2022 08:23

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