Implications of Local Friendliness violation for quantum causality

Abstract

We provide a new formulation of the Local Friendliness no-go theorem of Bong et al [Nat. Phys. 16, 1199 (2020)] from fundamental causal principles, providing another perspective on how it puts strictly stronger bounds on quantum reality than Bell's theorem. In particular, quantum causal models have been proposed as a way to maintain a peaceful coexistence between quantum mechanics and relativistic causality, while respecting Leibniz's methodological principle. This works for Bell's theorem but does not work for the Local Friendliness no-go theorem, which considers an extended Wigner's Friend scenario. More radical conceptual renewal is required; we suggest that cleaving to Leibniz's principle requires extending relativity to events themselves.

arXiv comment11 pages, 7 figures. This is an updated and extended version of a talk given by EGC at the "Causality in a quantum world" workshop at Anacapri in Sep. 2019, and at the Harvard Foundations of Physics mini-workshop on Causation [https://www.youtube.com/watch?v=4KKZzqTmqBE] in Oct 2020, with HMW joining as a co-author. v2: Published version. Minor terminological change; extended discussion

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Cited by in corpus (1)

• Consistency in the description of quantum measurement: Quantum theory can consistently describe the use of itself