2018/09/30 by Augustin Vanrietvelde, Philipp A. Hoehn, Philipp A Hoehn +2 · 3 citations
Physics and Astronomy · #Noncommutative and Quantum Gravity Theories #Observable #Open quantum system #Quantum #Quantum Mechanics and Applications #Quantum Mechanics and Non-Hermitian Physics #Quantum capacity #Quantum entanglement #Quantum information #Quantum operation #Quantum process #Quantum state #Reference frame #gr-qc #quant-ph
paper · pdf · doi:10.22331/q-2020-01-27-225
published as Quantum 4, 225 (2020) · Same as v3, just put into Quantum style for publication. Written in a manner also accessible to an audience unfamiliar with constrained systems. 26 pages + appendix, many figures
openalex created_date 2018/09/27 · arxiv created 2020/01/22 · openalex publication_date 2020/01/27 · arxiv updated 2020/01/29 · openalex updated_date 2026/08/06
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 \citeGiacomini: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.