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DTSTART;TZID=Europe/Madrid:20260422T113000
DTEND;TZID=Europe/Madrid:20260422T123000
DTSTAMP:20260722T163708
CREATED:20260420T064701Z
LAST-MODIFIED:20260420T064701Z
UID:24923-1776857400-1776861000@www.ift.uam-csic.es
SUMMARY:Quantum Information Journal Club: 'The Quantum Agreement Theorem'
DESCRIPTION:Title: The Quantum Agreement Theorem\n\nSpeaker: María García (upm)\n\nVenue&Time: Gray Room 3 / 11:30\n\nAbstract: We formulate and prove an Agreement Theorem for quantummechanics (QM)\, describing when two\nagents\, represented by separate laboratories\, can or cannot maintain differing probability estimates of\na shared quantum property of interest. Building on the classical framework (Aumann\, 1976)\, we define\nthe modality of “common certainty” through a hierarchy of certainty operators acting on each agent’s\nHilbert space. In the commuting case – when all measurements and event projectors commute – common\ncertainty leads to equality of the agents’ conditional probabilities\, recovering a QM analog of the classical\ntheorem. By contrast\, when non-commuting operators are allowed\, the certainty recursion can stabilize\nwith different probabilities. This yields common certainty of disagreement (CCD) as a distinctive QM\nphenomenon. Agreement is restored once measurement outcomes are recorded in a classical register. The\nclassical Agreement Theorem can therefore be seen as emergent from the quantum world via recording.\nWe establish an impossibility result stating that QM forbids a scenario where one agent is certain that\na property of interest occurs\, and is also certain that the other agent is certain that the property does\nnot occur. In this sense\, QM admits non-classical disagreement\, but disagreement is still bounded in a\ndisciplined way. We argue that our analysis offers a rigorous approach to the longstanding issue of how\nto understand intersubjectivity across agents in QM.
URL:https://www.ift.uam-csic.es/event/quantum-information-journal-club-the-quantum-agreement-theorem/
LOCATION:Gray Room 3\, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera\, 13-15\, Fuencarral-El Pardo\, Madrid\, 28049\,\, Spain
CATEGORIES:Journal clubs,Scientific activities
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