{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,9,13]],"date-time":"2025-09-13T16:40:53Z","timestamp":1757781653422},"reference-count":19,"publisher":"Verein zur Forderung des Open Access Publizierens in den Quantenwissenschaften","license":[{"start":{"date-parts":[[2024,9,25]],"date-time":"2024-09-25T00:00:00Z","timestamp":1727222400000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["quantum-journal.org"],"crossmark-restriction":false},"short-container-title":["Quantum"],"abstract":"The Wigner&apos;s friend experiment is a thought experiment in which a so-called superobserver (Wigner) observes another observer (the friend) who has performed a quantum measurement on a physical system. In this setup Wigner treats the friend, the system and potentially other degrees of freedom involved in the friend&apos;s measurement as one joint quantum system. In general, Wigner&apos;s measurement changes the internal record of the friend&apos;s measurement result such that after the measurement by the superobserver the result stored in the observer&apos;s memory register is no longer the same as the result the friend obtained initially, i.e. before she was measured by Wigner. Here, we show that any awareness by the friend of this change of her memory, which can be modeled by an additional register storing the information about the change, conflicts with the no-signaling condition in extended Wigner-friend scenarios.<\/jats:p>","DOI":"10.22331\/q-2024-09-25-1481","type":"journal-article","created":{"date-parts":[[2024,9,25]],"date-time":"2024-09-25T12:12:14Z","timestamp":1727266334000},"page":"1481","update-policy":"http:\/\/dx.doi.org\/10.22331\/q-crossmark-policy-page","source":"Crossref","is-referenced-by-count":3,"title":["Wigner&apos;s friend&apos;s memory and the no-signaling principle"],"prefix":"10.22331","volume":"8","author":[{"given":"Veronika","family":"Baumann","sequence":"first","affiliation":[{"name":"Institute for Quantum Optics and Quantum Information (IQOQI), Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Vienna, Austria"},{"name":"Atominstitut, Technische Universit\u00e4t Wien, 1020 Vienna, Austria"}]},{"given":"\u010caslav","family":"Brukner","sequence":"additional","affiliation":[{"name":"Institute for Quantum Optics and Quantum Information (IQOQI), Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Vienna, Austria"},{"name":"University of Vienna, Faculty of Physics, Boltzmanngasse 5, 1090 Vienna, Austria"}]}],"member":"9598","published-online":{"date-parts":[[2024,9,25]]},"reference":[{"key":"0","doi-asserted-by":"publisher","unstructured":"Eugene P Wigner. ``The problem of measurement''. American Journal of Physics 31, 6\u201315 (1963).","DOI":"10.1119\/1.1969254"},{"key":"1","doi-asserted-by":"publisher","unstructured":"Tim Maudlin. ``Three measurement problems''. Topoi 14, 7\u201315 (1995).","DOI":"10.1007\/BF00763473"},{"key":"2","doi-asserted-by":"publisher","unstructured":"Jeffrey Bub and Itamar Pitowsky. ``Two dogmas about quantum mechanics''. Many worldsPages 433\u2013459 (2010).","DOI":"10.1007\/978-3-030-34316-3_12"},{"key":"3","doi-asserted-by":"publisher","unstructured":"\u010caslav Brukner. ``On the quantum measurement problem''. In Quantum [Un] Speakables II. Pages 95\u2013117. Springer (2017).","DOI":"10.1007\/978-3-319-38987-5_5"},{"key":"4","doi-asserted-by":"publisher","unstructured":"Marek \u017bukowski and Marcin Markiewicz. ``Physics and metaphysics of wigner's friends: even performed premeasurements have no results''. 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International Journal of Theoretical Physics 24, 1\u201341 (1985).","DOI":"10.1007\/BF00670071"},{"key":"13","doi-asserted-by":"publisher","unstructured":"Veronika Baumann and Stefan Wolf. ``On formalisms and interpretations''. Quantum 2, 99 (2018).","DOI":"10.22331\/q-2018-10-15-99"},{"key":"14","doi-asserted-by":"publisher","unstructured":"Eric G Cavalcanti. ``The view from a wigner bubble''. Foundations of Physics 51, 39 (2021).","DOI":"10.1007\/s10701-021-00417-0"},{"key":"15","doi-asserted-by":"publisher","unstructured":"Veronika Baumann and \u010caslav Brukner. ``Wigner's friend as a rational agent''. In Quantum, Probability, Logic. Pages 91\u201399. Springer (2020).","DOI":"10.1007\/978-3-030-34316-3_4"},{"key":"16","doi-asserted-by":"publisher","unstructured":"Philippe Allard Gu\u00e9rin, Veronika Baumann, Flavio Del Santo, and \u010caslav Brukner. ``A no-go theorem for the persistent reality of wigner's friend's perception''. 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