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Quantum processes on time-delocalised systems

Banff International Research Station for Mathematical Innovation and Discovery

I will discuss the notion of time-delocalised quantum systems and its relevance to the question of realisability of processes with indefinite causal order in standard quantum theory and quantum gravity. I will explain how given a description of an experiment in the form of a (generally cyclic) circuit, the experiment can be described with respect to an arbitrary alternative choice of (sub)systems. This provides a very general notion of transformation between different equivalent descriptions of an experiment. I will review how the quantum SWITCH can be seen as realisable on time-delocalised systems in standard quantum mechanics and will show that all unitarily extendible tripartite processes admit such realisations. Notably, this includes processes violating causal inequalities, among which some purely classical ones. I will discuss the meaning of causal inequality violations with such time-delocalised variables. Finally, I will speculate on the link between time-delocalised systems and quantum reference frames.

Mathematics; Relativity And Gravitational Theory; Quantum Theory; Mathematical Physics

video/mp4

Author affiliation: Université libre de Bruxelles

2023-10-21

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/86248

Unreviewed

http://creativecommons.org/licenses/by-nc-nd/4.0/