Witnessing causal nonseparability

Araujo, Mateus, Branciard, Cyril, Costa, Fabio, Feix, Adrien, Giarmatzi, Christina and Brukner, Caslav (2015) Witnessing causal nonseparability. New Journal of Physics, 17 10: . doi:10.1088/1367-2630/17/10/102001

Author Araujo, Mateus
Branciard, Cyril
Costa, Fabio
Feix, Adrien
Giarmatzi, Christina
Brukner, Caslav
Title Witnessing causal nonseparability
Journal name New Journal of Physics   Check publisher's open access policy
ISSN 1367-2630
Publication date 2015-10-19
Year available 2015
Sub-type Article (original research)
DOI 10.1088/1367-2630/17/10/102001
Open Access Status DOI
Volume 17
Issue 10
Total pages 33
Place of publication Bristol, United Kingdom
Publisher Institute of Physics Publishing
Language eng
Formatted abstract
Our common understanding of the physical world deeply relies on the notion that events are ordered with respect to some time parameter, with past events serving as causes for future ones. Nonetheless, it was recently found that it is possible to formulate quantum mechanics without any reference to a global time or causal structure. The resulting framework includes new kinds of quantum resources that allow performing tasks—in particular, the violation ofcausal inequalities—which are impossible for events ordered according to a global causal order. However, no physical implementation of such resources is known. Here we show that a recently demonstrated resource for quantum computation—the quantum switch—is a genuine example of ‘indefinite causal order’. We do this by introducing a new tool—the causal witness—which can detect the causal nonseparability of any quantum resource that is incompatible with a definite causal order. We show however that the quantum switch does not violate any causal inequality.
Keyword Causality
Quantum foundations
Quantum information
Q-Index Code C1
Q-Index Status Confirmed Code
Grant ID 323970
TWCF 0064/AB38
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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Citation counts: TR Web of Science Citation Count  Cited 16 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 17 times in Scopus Article | Citations
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Created: Tue, 24 Nov 2015, 10:36:00 EST by System User on behalf of Engineered Quantum Systems