The simplest causal inequalities and their violation

Branciard, Cyril Branciard, Araujo, Mateus, Feix, Adrien, Costa, Fabio and Brukner, Caslav (2015) The simplest causal inequalities and their violation. New Journal of Physics, 18 1: . doi:10.1088/1367-2630/18/1/013008

Author Branciard, Cyril Branciard
Araujo, Mateus
Feix, Adrien
Costa, Fabio
Brukner, Caslav
Title The simplest causal inequalities and their violation
Journal name New Journal of Physics   Check publisher's open access policy
ISSN 1367-2630
Publication date 2015-12-23
Sub-type Article (original research)
DOI 10.1088/1367-2630/18/1/013008
Open Access Status DOI
Volume 18
Issue 1
Total pages 13
Place of publication Bristol, United Kingdom
Publisher Institute of Physics Publishing
Collection year 2016
Language eng
Formatted abstract
In a scenario where two parties share, act on and exchange some physical resource, the assumption that the parties' actions are ordered according to a definite causal structure yields constraints on the possible correlations that can be established. We show that the set of correlations that are compatible with a definite causal order forms a polytope, whose facets define causal inequalities. We fully characterize this causal polytope in the simplest case of bipartite correlations with binary inputs and outputs. We find two families of nonequivalent causal inequalities; both can be violated in the recently introduced framework of process matrices, which extends the standard quantum formalism by relaxing the implicit assumption of a fixed causal structure. Our work paves the way to a more systematic investigation of causal inequalities in a theory-independent way, and of their violation within the framework of process matrices.
Keyword Causal inequalities
Device-independent tests of correlations
Indefinite causal order
Quantum causality
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Mathematics and Physics
Official 2016 Collection
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