Observers of quantum systems cannot agree to disagree
- URL: http://arxiv.org/abs/2102.08966v3
- Date: Thu, 2 Dec 2021 15:11:59 GMT
- Title: Observers of quantum systems cannot agree to disagree
- Authors: Patricia Contreras-Tejada, Giannicola Scarpa, Aleksander M. Kubicki,
Adam Brandenburger and Pierfranceso La Mura
- Abstract summary: We ask whether agreement between observers can serve as a physical principle that must hold for any theory of the world.
We construct examples of (postquantum) no-signaling boxes where observers can agree to disagree.
- Score: 55.41644538483948
- License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
- Abstract: 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.
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