{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,26]],"date-time":"2025-12-26T11:31:26Z","timestamp":1766748686867},"reference-count":41,"publisher":"Verein zur Forderung des Open Access Publizierens in den Quantenwissenschaften","license":[{"start":{"date-parts":[[2024,2,27]],"date-time":"2024-02-27T00:00:00Z","timestamp":1708992000000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Schr\u00f6dinger Fellowship, FWF","award":["J 4699"],"award-info":[{"award-number":["J 4699"]}]},{"DOI":"10.13039\/501100001711","name":"SNSF","doi-asserted-by":"crossref","award":["NCCR-SwissMap"],"award-info":[{"award-number":["NCCR-SwissMap"]}],"id":[{"id":"10.13039\/501100001711","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":["quantum-journal.org"],"crossmark-restriction":false},"short-container-title":["Quantum"],"abstract":"Naive attempts to put together relativity and quantum measurements lead to signaling between space-like separated regions. In QFT, these are known as impossible measurements<\/mml:mtext><\/mml:mrow><\/mml:math>. We show that the same problem arises in non-relativistic quantum physics, where joint nonlocal measurements (i.e., between systems kept spatially separated) in general lead to signaling, while one would expect no-signaling (based for instance on the principle of no-nonphysical communication<\/mml:mtext><\/mml:mrow><\/mml:math>). This raises the question: Which nonlocal quantum measurements are physically possible? We review and develop further a non-relativistic quantum information approach developed independently of the impossible measurements in QFT, and show that these two have been addressing virtually the same problem. The non-relativistic solution shows that all nonlocal measurements are l<\/mml:mi>o<\/mml:mi>c<\/mml:mi>a<\/mml:mi>l<\/mml:mi>i<\/mml:mi>z<\/mml:mi>a<\/mml:mi>b<\/mml:mi>l<\/mml:mi>e<\/mml:mi><\/mml:math> (i.e., they can be carried out at a distance without violating no-signaling) but they (i) may require arbitrarily large entangled resources and (ii) cannot in general be i<\/mml:mi>d<\/mml:mi>e<\/mml:mi>a<\/mml:mi>l<\/mml:mi><\/mml:math>, i.e., are not immediately reproducible. These considerations could help guide the development of a complete theory of measurement in QFT.<\/jats:p>","DOI":"10.22331\/q-2024-02-27-1267","type":"journal-article","created":{"date-parts":[[2024,2,27]],"date-time":"2024-02-27T10:39:58Z","timestamp":1709030398000},"page":"1267","update-policy":"http:\/\/dx.doi.org\/10.22331\/q-crossmark-policy-page","source":"Crossref","is-referenced-by-count":4,"title":["Towards a measurement theory in QFT: \"Impossible\" quantum measurements are possible but not ideal"],"prefix":"10.22331","volume":"8","author":[{"given":"Nicolas","family":"Gisin","sequence":"first","affiliation":[{"name":"Group of Applied Physics, University of Geneva, 1211 Geneva, Switzerland"},{"name":"Constructor University, Geneva, Switzerland"}]},{"given":"Flavio","family":"Del Santo","sequence":"additional","affiliation":[{"name":"Group of Applied Physics, University of Geneva, 1211 Geneva, Switzerland"},{"name":"Constructor University, Geneva, Switzerland"}]}],"member":"9598","published-online":{"date-parts":[[2024,2,27]]},"reference":[{"key":"0","doi-asserted-by":"crossref","unstructured":"Lev Landau and Rudolf Peierls. ``Erweiterung des Unbestimmtheitsprinzips f\u00fcr die relativistische Quantentheorie''. 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