Indefinite Causal Order in a Quantum Switch.

Goswami, K; Giarmatzi, C; Kewming, M; Costa, F; Branciard, C; Romero, J; White, AG

Indefinite Causal Order in a Quantum Switch.

Goswami, K Giarmatzi, C

Kewming, M Costa, F Branciard, C Romero, J White, AG

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Publisher:: AMER PHYSICAL SOC
Publication Type:: Journal Article
Citation:: Phys Rev Lett, 2018, 121, (9), pp. 090503
Issue Date:: 2018-08-31

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Field	Value	Language
dc.contributor.author	Goswami, K
dc.contributor.author	Giarmatzi, C https://orcid.org/0000-0001-8254-2169
dc.contributor.author	Kewming, M
dc.contributor.author	Costa, F
dc.contributor.author	Branciard, C
dc.contributor.author	Romero, J
dc.contributor.author	White, AG
dc.date.accessioned	2022-09-07T22:07:22Z
dc.date.available	2022-09-07T22:07:22Z
dc.date.issued	2018-08-31
dc.identifier.citation	Phys Rev Lett, 2018, 121, (9), pp. 090503
dc.identifier.issn	0031-9007
dc.identifier.issn	1079-7114
dc.identifier.uri	http://hdl.handle.net/10453/161492
dc.description.abstract	Quantum mechanics allows events to happen with no definite causal order: this can be verified by measuring a causal witness, in the same way that an entanglement witness verifies entanglement. Here, we realize a photonic quantum switch, where two operations A[over ^] and B[over ^] act in a quantum superposition of their two possible orders. The operations are on the transverse spatial mode of the photons; polarization coherently controls their order. Our implementation ensures that the operations cannot be distinguished by spatial or temporal position-further it allows qudit encoding in the target. We confirm our quantum switch has no definite causal order by constructing a causal witness and measuring its value to be 18 standard deviations beyond the definite-order bound.
dc.format	Print
dc.language	eng
dc.publisher	AMER PHYSICAL SOC
dc.relation.ispartof	Phys Rev Lett
dc.relation.isbasedon	10.1103/PhysRevLett.121.090503
dc.rights	info:eu-repo/semantics/closedAccess
dc.subject	01 Mathematical Sciences, 02 Physical Sciences, 09 Engineering
dc.subject.classification	General Physics
dc.title	Indefinite Causal Order in a Quantum Switch.
dc.type	Journal Article
utslib.citation.volume	121
utslib.location.activity	United States
utslib.for	01 Mathematical Sciences
utslib.for	02 Physical Sciences
utslib.for	09 Engineering
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Engineering and Information Technology
utslib.copyright.status	closed_access	*
dc.date.updated	2022-09-07T22:07:20Z
pubs.issue	9
pubs.publication-status	Published
pubs.volume	121
utslib.citation.issue	9

Abstract:

Quantum mechanics allows events to happen with no definite causal order: this can be verified by measuring a causal witness, in the same way that an entanglement witness verifies entanglement. Here, we realize a photonic quantum switch, where two operations A[over ^] and B[over ^] act in a quantum superposition of their two possible orders. The operations are on the transverse spatial mode of the photons; polarization coherently controls their order. Our implementation ensures that the operations cannot be distinguished by spatial or temporal position-further it allows qudit encoding in the target. We confirm our quantum switch has no definite causal order by constructing a causal witness and measuring its value to be 18 standard deviations beyond the definite-order bound.

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