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Experimental Characterization of Unsharp Qubit Observables and Sequential Measurement Incompatibility via Quantum Random Access Codes
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics.
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Number of Authors: 62020 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 125, no 8, article id 080403Article in journal (Refereed) Published
Abstract [en]

Unsharp measurements are increasingly important for foundational insights in quantum theory and quantum information applications. Here, we report an experimental implementation of unsharp qubit measurements in a sequential communication protocol, based on a quantum random access code. The protocol involves three parties; the first party prepares a qubit system, the second party performs operations that return both a classical and quantum outcome, and the latter is measured by the third party. We demonstrate a nearly optimal sequential quantum random access code that outperforms both the best possible classical protocol and any quantum protocol that utilizes only projective measurements. Furthermore, while only assuming that the involved devices operate on qubits and that detected events constitute a fair sample, we demonstrate the noise-robust characterization of unsharp measurements based on the sequential quantum random access code. We apply this characterization towards quantifying the degree of incompatibility of two sequential pairs of quantum measurements.

Place, publisher, year, edition, pages
2020. Vol. 125, no 8, article id 080403
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:su:diva-185171DOI: 10.1103/PhysRevLett.125.080403ISI: 000560626400002OAI: oai:DiVA.org:su-185171DiVA, id: diva2:1468335
Available from: 2020-09-17 Created: 2020-09-17 Last updated: 2022-03-23Bibliographically approved
In thesis
1. Photonic Multipartite Communication: Complexity, measurements and Bell inequalities
Open this publication in new window or tab >>Photonic Multipartite Communication: Complexity, measurements and Bell inequalities
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The interdisciplinary field of quantum communication and quantum information processing merges quantum mechanics, optics, photonics, information processing, and electronics to solve information and communication tasks that are impossible to solve efficiently with classical resources. Here in this thesis experimental demonstrations of some of such tasks are presented. In particular, using a single qubit system and quantum Zeno effect we investigated a class of communication complexity problems (CCP) for multi-parties. As solutions, three different quantum strategies are evaluated by proof of concept experimental demonstrations. Our results go beyond the classical limits. Furthermore, the same single qubit system is used to show that preparation contextuality can be shared among multiple observers through a quantum state ensemble while implementing sequential unsharp measurement. We showed that this is possible for any amount of white noise and presented experimental demonstration for three parties. In addition, characterization of unsharp measurements based on quantum random access code and quantifying the degree of incompatibility of sequential measurements in a wide range of sharpness parameters are also presented.

Finally, I present the experimental generation of multi-photon entanglement to meet the basic requirement of modern quantum information processing.Using this source we produced a state with high fidelity that can violate a tight Bell inequality maximally with maximally incompatible local measurements.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2021. p. 85
National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-189572 (URN)978-91-7911-418-3 (ISBN)978-91-7911-419-0 (ISBN)
Public defence
2021-03-05, sal C5:1007, AlbaNova universitetscentrum, Roslagstullsbacken 21, online via Zoom, public link https://stockholmuniversity.zoom.us/j/64005105009, Stockholm, 09:00 (English)
Opponent
Supervisors
Funder
Knut and Alice Wallenberg Foundation
Available from: 2021-02-10 Created: 2021-01-26 Last updated: 2022-02-25Bibliographically approved

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Anwer, HammadMuhammad, SadiqCherifi, WalidTavakoli, ArminBourennane, Mohamed

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