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Experimental bound entanglement through a Pauli channel
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics.
2013 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 3, 1966Article in journal (Refereed) Published
Abstract [en]

Understanding the characteristics of a quantum systems when affected by noise is one of the biggest challenges for quantum technologies. The general Pauli error channel is an important lossless channel for quantum communication. In this work we consider the effects of a Pauli channel on a pure four-qubit state and simulate the Pauli channel experimentally by studying the action on polarization encoded entangled photons. When the noise channel acting on the photons is correlated, a set spanned by four orthogonal bound entangled states can be generated. We study this interesting case experimentally and demonstrate that products of Bell states can be brought into a bound entangled regime. We find states in the set of bound entangled states which experimentally violate the CHSH inequality while still possessing a positive partial transpose.

Place, publisher, year, edition, pages
2013. Vol. 3, 1966
National Category
Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
URN: urn:nbn:se:su:diva-66457DOI: 10.1038/srep01966ISI: 000320130300005OAI: oai:DiVA.org:su-66457DiVA: diva2:467974
Available from: 2011-12-20 Created: 2011-12-20 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
2. Experiments with Entangled Photons: Bell Inequalities, Non-local Games and Bound Entanglement
Open this publication in new window or tab >>Experiments with Entangled Photons: Bell Inequalities, Non-local Games and Bound Entanglement
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Quantum mechanics is undoubtedly a weird field of science, which violates many deep conceptual tenets of classical physics, requiring reconsideration of the concepts on which classical physics is based. For instance, it permits persistent correlations between classically separated systems, that are termed as entanglement. To circumvent these problems and explain entanglement, hidden variables theories--based on undiscovered parameters--have been devised. However, John S. Bell and others invented inequalities that can distinguish between the predictions of local hidden variable (LHV) theories and quantum mechanics. The CHSH-inequality (formulated by J. Clauser, M. Horne, A. Shimony and R. A. Holt), is one of the most famous among these inequalities. In the present work, we found that this inequality actually contains an even simpler logical structure, which can itself be described by an inequality and will be violated by quantum mechanics. We found 3 simpler inequalities and were able to violate them experimentally.

Furthermore, the CHSH inequality can be used to devise games that can outperform classical strategies. We explore CHSH-games for biased and unbiased cases and present their experimental realizations. We also found a remarkable application of CHSH-games in real life, namely in the card game of duplicate Bridge.  In this thesis, we have described this application along with its experimental realization. Moreover, non-local games with quantum inputs can be used to certify entanglement in a measurement device independent manner. We implemented this method and detected entanglement in a set of two-photon Werner states. Our results are in good agreement with theory.

A peculiar form of entanglement that is not distillable through local operations and classical communication (LOCC) is known as bound entanglement (BE). In the present work, we produced and studied BE in four-partite Smolin states and present an experimental violation of a Bell inequality by such states. Moreover we produced a three-qubit BE state, which is also the first experimental realization of a tripartite BE state. We also present its activation, where we experimentally demonstrate super additivity of quantum information resources.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2016. 89 p.
National Category
Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-128277 (URN)978-91-7649-358-8 (ISBN)
Public defence
2016-04-28, FP41, AlbaNova universitetscentrum, Roslagstullsbacken 33, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

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

Available from: 2016-04-05 Created: 2016-03-22 Last updated: 2017-02-24Bibliographically approved

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