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Experimental four-qubit bound entanglement
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics.
2009 (English)In: Nature Physics, ISSN 1745-2473, E-ISSN 1745-2481, Vol. 5, no 10, 748-752 p.Article in journal (Refereed) Published
Abstract [en]

Entanglement is one of the most puzzling features of quantum theory and of great importance for the new field of quantum information. Being a peculiar form of entanglement, bound entanglement emerges in certain mixed quantum states. This form of entanglement is not distillable by local operators and classical communication. Bound-entangled states are different from both the free entangled (distillable) and separable states. Here we report on the first experimental demonstration of a four-qubit polarization bound-entangled state, the so-called Smolin state. We have fully characterized its entanglement properties. Moreover, we have realized unlocking of the entanglement protocol for this state. The special properties of the Smolin state constitute a useful quantum resource for new multiparty communication schemes.

Place, publisher, year, edition, pages
2009. Vol. 5, no 10, 748-752 p.
Keyword [en]
mixed states, separability criterion, density-matrices, quantum
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:su:diva-59659DOI: 10.1038/NPHYS1372ISI: 000271185400016OAI: oai:DiVA.org:su-59659DiVA: diva2:432149
Note
authorCount :2Available from: 2011-08-01 Created: 2011-07-05 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Dynamics of Quantum Correlations with Photons: Experiments on bound entanglement and contextuality for application in quantum information
Open this publication in new window or tab >>Dynamics of Quantum Correlations with Photons: Experiments on bound entanglement and contextuality for application in quantum information
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The rapidly developing interdisciplinary field of quantum information, which merges quantum and information science, studies non-classical aspects of quantum systems. These studies are motivated by the promise that the non-classicality can be used to solve tasks more efficiently than classical methods would allow. In many quantum informational studies, non-classical behaviour is attributed to the notion of entanglement.

In this thesis we use photons to experimentally investigate fundamental questions such as: What happens to the entanglement in a system when it is affected by noise? In our study of noisy entanglement we pursue the challenging task of creating bound entanglement. Bound entangled states are created through an irreversible process that requires entanglement. Once in the bound regime, entanglement cannot be distilled out through local operations assisted by classical communication. We show that it is possible to experimentally produce four-photon bound entangled states and that a violation of a Bell inequality can be achieved. Moreover, we demonstrate an entanglement-unlocking protocol by relaxing the condition of local operations.

We also explore the non-classical nature of quantum mechanics in several single-photon experiments. In these experiments, we show the violation of various inequalities that were derived under the assumption of non-contextuality. Using qutrits we construct and demonstrate the simplest possible test that offers a discrepancy between classical and quantum theory. Furthermore, we perform an experiment in the spirit of the Kochen-Specker theorem to illustrate the state-independence of this theorem. Here, we investigate whether or not measurement outcomes exhibit fully contextual correlations. That is, no part of the correlations can be attributed to the non-contextual theory. Our results show that only a small part of the experimental generated correlations are amenable to a non-contextual interpretation.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2012. 102 p.
Keyword
Quantum information, quantum optics, foundations of quantum mechanics, entanglement, non-contextuality, Kochen-Specker theorem, parametric down-conversion, quantum state engineering
National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-66469 (URN)978-91-7447-421-3 (ISBN)
Public defence
2012-01-26, FA31, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 5: Submitted. Paper 6: Submitted.

Available from: 2012-01-04 Created: 2011-12-20 Last updated: 2015-04-30Bibliographically approved

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