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Quantum Relativity of Subsystems Galley, Thomas


One of the most basic notions in physics is the partitioning of a system into subsystems, and the study of correlations among its parts. In this talk, we will explore these notions in the context of quantum reference frame (QRF) covariance, in which this partitioning is subject to a symmetry constraint. We will see that different reference frame perspectives induce different sets of subsystem observable algebras, which leads to a gauge-invariant, frame-dependent notion of subsystems and entanglement. We will then see that subalgebras which commute before imposing the symmetry constraint can translate into non-commuting algebras in a given QRF perspective after symmetry imposition. Such a QRF perspective does not inherit the distinction between subsystems in terms of the corresponding tensor factorizability of the kinematical Hilbert space and observable algebra. Since the condition for this to occur is contingent on the choice of QRF, the notion of subsystem locality is frame-dependent. Finally I will comment on the relevance of these results for existing programs in quantum gravity, as well as relate them to existing results on the relativity of quantum systems within approaches in quantum information. This talk is based on joint work with Philipp A. Hoehn, Maximilian P. E. Lock, Shadi Ali Ahmad and Alexander R. H. Smith which can be found at

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