{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,8]],"date-time":"2026-06-08T22:56:50Z","timestamp":1780959410989,"version":"3.54.1"},"reference-count":96,"publisher":"Verein zur Forderung des Open Access Publizierens in den Quantenwissenschaften","license":[{"start":{"date-parts":[[2020,1,27]],"date-time":"2020-01-27T00:00:00Z","timestamp":1580083200000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Quantum"],"abstract":"<jats:p>Treating reference frames fundamentally as quantum systems is inevitable in quantum gravity and also in quantum foundations once considering laboratories as physical systems. Both fields thereby face the question of how to describe physics relative to quantum reference systems and how the descriptions relative to different such choices are related. Here, we exploit a fruitful interplay of ideas from both fields to begin developing a unifying approach to transformations among quantum reference systems that ultimately aims at encompassing both quantum and gravitational physics. In particular, using a gravity inspired symmetry principle, which enforces physical observables to be relational and leads to an inherent redundancy in the description, we develop a perspective-neutral structure, which contains all frame perspectives at once and via which they are changed. We show that taking the perspective of a specific frame amounts to a fixing of the symmetry related redundancies in both the classical and quantum theory and that changing perspective corresponds to a symmetry transformation. We implement this using the language of constrained systems, which naturally encodes symmetries. Within a simple one-dimensional model, we recover some of the quantum frame transformations of \\cite{Giacomini:2017zju}, embedding them in a perspective-neutral framework. Using them, we illustrate how entanglement and classicality of an observed system depend on the quantum frame perspective. Our operational language also inspires a new interpretation of Dirac and reduced quantized theories within our model as perspective-neutral and perspectival quantum theories, respectively, and reveals the explicit link between them. In this light, we suggest a new take on the relation between a `quantum general covariance' and the diffeomorphism symmetry in quantum gravity.<\/jats:p>","DOI":"10.22331\/q-2020-01-27-225","type":"journal-article","created":{"date-parts":[[2020,1,27]],"date-time":"2020-01-27T15:42:42Z","timestamp":1580139762000},"page":"225","source":"Crossref","is-referenced-by-count":129,"title":["A change of perspective: switching quantum reference frames via a perspective-neutral framework"],"prefix":"10.22331","volume":"4","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9022-8655","authenticated-orcid":false,"given":"Augustin","family":"Vanrietvelde","sequence":"first","affiliation":[{"name":"Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Vienna, Austria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7108-1184","authenticated-orcid":false,"given":"Philipp A.","family":"Hoehn","sequence":"additional","affiliation":[{"name":"Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Vienna, Austria"},{"name":"Vienna Center for Quantum Science and Technology (VCQ), Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Flaminia","family":"Giacomini","sequence":"additional","affiliation":[{"name":"Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Vienna, Austria"},{"name":"Vienna Center for Quantum Science and Technology (VCQ), Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Esteban","family":"Castro-Ruiz","sequence":"additional","affiliation":[{"name":"Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Vienna, Austria"},{"name":"Vienna Center for Quantum Science and Technology (VCQ), Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"9598","published-online":{"date-parts":[[2020,1,27]]},"reference":[{"key":"0","doi-asserted-by":"publisher","unstructured":"F. 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H\u00f6hn, ``Effective changes of quantum reference systems in quantum phase space,'' to appear (2020)."},{"key":"5","doi-asserted-by":"publisher","unstructured":"Y. Aharonov and L. Susskind, ``Charge Superselection Rule,'' Phys. Rev. 155 (1967) 1428-1431.","DOI":"10.1103\/PhysRev.155.1428"},{"key":"6","doi-asserted-by":"publisher","unstructured":"B. S. DeWitt, ``Quantum theory of gravity. I. The canonical theory,'' Phys.Rev. 160 (1967) 1113-1148.","DOI":"10.1103\/PhysRev.160.1113"},{"key":"7","doi-asserted-by":"publisher","unstructured":"C. Rovelli, Quantum Gravity. Cambridge University Press, 2004.","DOI":"10.1017\/CBO9780511755804"},{"key":"8","doi-asserted-by":"publisher","unstructured":"J. Barbour and B. 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Tsobanjan, ``Effective relational dynamics of a nonintegrable cosmological model,'' Phys.Rev. D86 (2012) 065014, arXiv:1111.5193 [gr-qc].","DOI":"10.1103\/PhysRevD.86.065014"},{"key":"24","doi-asserted-by":"publisher","unstructured":"Y. Aharonov and L. Susskind, ``Observability of the sign change of spinors under $2{\\pi}$ rotations,'' Phys. Rev. 158 (Jun, 1967) 1237-1238.","DOI":"10.1103\/PhysRev.158.1237"},{"key":"25","doi-asserted-by":"publisher","unstructured":"Y. Aharonov and T. Kaufherr, ``Quantum frames of reference,'' Phys. Rev. D 30 (Jul, 1984) 368-385.","DOI":"10.1103\/PhysRevD.30.368"},{"key":"26","doi-asserted-by":"publisher","unstructured":"S. D. Bartlett, T. Rudolph, and R. W. Spekkens, ``Reference frames, superselection rules, and quantum information,'' Rev. Mod. Phys. 79 (2007) 555-609, arXiv:quant-ph\/0610030.","DOI":"10.1103\/RevModPhys.79.555"},{"key":"27","doi-asserted-by":"publisher","unstructured":"S. D. Bartlett, T. Rudolph, R. W. Spekkens, and P. S. 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