Titel
Witnessing causal nonseparability
Autor*in
Cyril Branciard
Institut Néel, CNRS and Université Grenoble Alpes
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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 of causal 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.
Stichwort
quantum informationcausalityquantum foundations
Objekt-Typ
Sprache
Englisch [eng]
Persistent identifier
phaidra.univie.ac.at/o:448416
Erschienen in
Titel
New Journal of Physics
Band
17
Ausgabe
10
Seitenanfang
102001
Publication
IOP Publishing
Erscheinungsdatum
2015
Zugänglichkeit
Rechte
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