Quantum Theory Cannot Violate a Causal Inequality

Tom Purves and Anthony J. Short
Phys. Rev. Lett. 127, 110402 – Published 10 September 2021
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Abstract

Within quantum theory, we can create superpositions of different causal orders of events, and observe interference between them. This raises the question of whether quantum theory can produce results that would be impossible to replicate with any classical causal model, thereby violating a causal inequality. This would be a temporal analog of Bell inequality violation, which proves that no local hidden variable model can replicate quantum results. However, unlike the case of nonlocality, we show that quantum experiments can be simulated by a classical causal model, and therefore cannot violate a causal inequality.

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  • Received 3 June 2021
  • Accepted 17 August 2021

DOI:https://doi.org/10.1103/PhysRevLett.127.110402

© 2021 American Physical Society

Physics Subject Headings (PhySH)

Quantum Information, Science & TechnologyGeneral Physics

Authors & Affiliations

Tom Purves* and Anthony J. Short

  • H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, United Kingdom

  • *tom.purves@bristol.ac.uk
  • tony.short@bristol.ac.uk

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Issue

Vol. 127, Iss. 11 — 10 September 2021

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