Bell’s theorem for temporal order

Magdalena Zych, Fabio Costa, Igor Pikovski, Časlav Brukner

Research output: Contribution to journalArticlepeer-review

94 Scopus citations

Abstract

Time has a fundamentally different character in quantum mechanics and in general relativity. In quantum theory events unfold in a fixed order while in general relativity temporal order is influenced by the distribution of matter. When matter requires a quantum description, temporal order is expected to become non-classical—a scenario beyond the scope of current theories. Here we provide a direct description of such a scenario. We consider a thought experiment with a massive body in a spatial superposition and show how it leads to entanglement of temporal orders between time-like events. This entanglement enables accomplishing a task, violation of a Bell inequality, that is impossible under local classical temporal order; it means that temporal order cannot be described by any pre-defined local variables. A classical notion of a causal structure is therefore untenable in any framework compatible with the basic principles of quantum mechanics and classical general relativity.

Original languageEnglish
Article number3772
JournalNature Communications
Volume10
Issue number1
DOIs
StatePublished - 1 Dec 2019

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