Inadequacy of Modal Logic in Quantum Settings


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Date

2019-01-31

Publication Type

Conference Paper

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yes

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Abstract

We test the principles of classical modal logic in fully quantum settings. Modal logic models our reasoning in multi-agent problems, and allows us to solve puzzles like the muddy children paradox. The Frauchiger-Renner thought experiment highlighted fundamental problems in applying classical reasoning when quantum agents are involved; we take it as a guiding example to test the axioms of classical modal logic. In doing so, we find a problem in the original formulation of the Frauchiger-Renner theorem: a missing assumption about unitarity of evolution is necessary to derive a contradiction and prove the theorem. Adding this assumption clarifies how different interpretations of quantum theory fit in, i.e., which properties they violate. Finally, we show how most of the axioms of classical modal logic break down in quantum settings, and attempt to generalize them. Namely, we introduce constructions of trust and context, which highlight the importance of an exact structure of trust relations between agents. We propose a challenge to the community: to find conditions for the validity of trust relations, strong enough to exorcise the paradox and weak enough to still recover classical logic.

Publication status

published

Book title

Proceedings of the 15th International Conference on Quantum Physics and Logic

Volume

287

Pages / Article No.

267 - 297

Publisher

Open Publishing Association

Event

15th International Conference on Quantum Physics and Logic (QPL 2018)

Edition / version

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Software

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Organisational unit

03781 - Renner, Renato / Renner, Renato check_circle

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