Everyone is welcome to attend the online QuSoft seminar, this week with Giannicola Scarpa. Title of the lecture: Agreement between observers, a physical principle?
Abstract:
An active research line in quantum foundations is devoted to finding constraints that can rule out post-quantum theories and single out quantum mechanics. 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. The seminal Agreement Theorem by Aumann states that two (classical) agents cannot agree to disagree, i.e., they cannot reach different and correct estimates about the probability of an event of interest, and have mutual knowledge about these estimates. We propose an extension of this theorem to no-signalling settings. In particular, we establish an Agreement Theorem for quantum agents, while we construct examples of (post-quantum) no-signalling boxes where agents can agree to disagree. Some of these examples belong to the class of "almost quantum", introduced by Navascués et al. in 2014. 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.
This is work in progress, joint with Adam Brandenburger, Patricia Contreras-Tejada, Aleksander Kubicki and Pierfrancesco La Mura.
If you would like to attend, please contact Jop Briët (j.briet@cwi.nl) or Subhasree Patro (Subhasree.Patro@cwi.nl).