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Entanglement distribution over a 96-km-long submarine optical fiber
Austrian Acad Sci, Inst Quantum Opt & Quantum Informat Vienna, A-1090 Vienna, Austria.;Vienna Ctr Quantum Sci & Technol, A-1090 Vienna, Austria..
Austrian Acad Sci, Inst Quantum Opt & Quantum Informat Vienna, A-1090 Vienna, Austria.;Vienna Ctr Quantum Sci & Technol, A-1090 Vienna, Austria.;HH Wills Phys Lab, Quantum Engn Technol Labs, Bristol BS8 1FD, Avon, England.;Univ Bristol, Dept Elect & Elect Engn, Bristol BS8 1UB, Avon, England..
Austrian Acad Sci, Inst Quantum Opt & Quantum Informat Vienna, A-1090 Vienna, Austria.;Vienna Ctr Quantum Sci & Technol, A-1090 Vienna, Austria.;Fraunhofer Inst Appl Opt & Precis Engn IOF Jena, D-07745 Jena, Germany.;Friedrich Schiller Univ Jena, Abbe Ctr Photon, D-07745 Jena, Germany..
KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. Single Quantum BV, NL-2628 CJ Delft, Netherlands..ORCID iD: 0000-0003-1831-2208
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2019 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 116, no 14, p. 6684-6688Article in journal (Refereed) Published
Abstract [en]

Quantum entanglement is one of the most extraordinary effects in quantum physics, with many applications in the emerging field of quantum information science. In particular, it provides the foundation for quantum key distribution (QKD), which promises a conceptual leap in information security. Entanglement-based QKD holds great promise for future applications owing to the possibility of device-independent security and the potential of establishing global-scale quantum repeater networks. While other approaches to QKD have already reached the level of maturity required for operation in absence of typical laboratory infrastructure, comparable field demonstrations of entanglement-based QKD have not been performed so far. Here, we report on the successful distribution of polarization-entangled photon pairs between Malta and Sicily over 96 km of submarine optical telecommunications fiber. We observe around 257 photon pairs per second, with a polarization visibility above 90%. Our results show that QKD based on polarization entanglement is now indeed viable in long-distance fiber links. This field demonstration marks the longest-distance distribution of entanglement in a deployed telecommunications network and demonstrates an international submarine quantum communication channel. This opens up myriad possibilities for future experiments and technological applications using existing infrastructure.

Place, publisher, year, edition, pages
NATL ACAD SCIENCES , 2019. Vol. 116, no 14, p. 6684-6688
Keywords [en]
quantum entanglement, quantum key distribution, quantum cryptography, polarization-entangled photons
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-249792DOI: 10.1073/pnas.1818752116ISI: 000463069900034PubMedID: 30872476Scopus ID: 2-s2.0-85064055529OAI: oai:DiVA.org:kth-249792DiVA, id: diva2:1306650
Conference
AUSER JF, 1969, PHYSICAL REVIEW LETTERS, V23, P880
Note

QC 20190424

Available from: 2019-04-24 Created: 2019-04-24 Last updated: 2019-05-28Bibliographically approved
In thesis
1. NbTiN for improved superconducting detectors
Open this publication in new window or tab >>NbTiN for improved superconducting detectors
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The physics of single photons is fascinating, by manipulating them we can observe and probe quantum effects. Doing so requires the fabrication and utilization of single photon sources, of which many types have been developed including quantum dots, trapped atoms and ions, and color centers. On the other end of the experiments, single photon detectors play a role of utmost importance, and while several types of detectors exist, superconducting nanowire single photon detectors are now the state-of-the-art technology. By offering near unity detection efficiency from the ultra-violet to the mid-infrared light spectrum, with negligible noise and excellent time resolution, they made possible many experiments that were previously technologically unfeasible. The same appealing characteristics have found a use in applications outside of the quantum optics framework, with notably light detection and ranging, biomedical imaging or CMOS circuits testing.In this thesis a controlled growth method for tailoring the characteristics of niobium titanium nitride in the framework of superconducting nanowire single photon detectors was developed. Reactive co-sputter deposition of niobium titanium nitride was shown to be a versatile method, both in terms of the degree of control over the material composition, and in the choice of substrates that it allows. Unity internal detection efficiency of detectors at telecom wavelengths was achieved by optimizing the niobium content in the material. The influence of lattice matching on the critical temperatures of films deposited at room temperature was investigated. The fabrication of superconducting nanowire single photon detectors on aluminum nitride-on-sapphire, on lithium niobate nano-waveguides, on gallium arsenide, and the integration on SiN waveguides was achieved. The material was used to fabricate detectors with optimized response for any linear polarization of the incoming photons by using a fractal architecture. Another method was proposed to achieve the same results by encapsulating meandering detectors in a high index dielectric material, resulting in a decrease of the permittivity mismatch between the nanowire material and its surrounding and therefore optimizing the efficiency for both orthogonal linear polarizations.Finally, detectors were fabricated from films developed in this work, and were operated to enable the implementation of polarization-based entanglement distribution in optical fibers in a real-conditions scenario, over a record distance of 96 km. This paves the way for the development of quantum communication networks using existing optical fiber links.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2019. p. iii-xviii, 66
Series
TRITA-SCI-GRU ; 2019:34
Keywords
superconducting nanowire sngle photon detector, SNSPD, niobium titanium nitride, NbTiN, reactive co-sputtering, quantum communications, quantum sensing
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-251759 (URN)978-91-7873-192-3 (ISBN)
Public defence
2019-06-14, FB42, Roslagstullbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
EU, European Research Council, 307687Swedish Research Council, 638-2013-7152
Note

QC 20190521

Available from: 2019-05-21 Created: 2019-05-21 Last updated: 2019-05-22Bibliographically approved

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Zichi, JulienZwiller, ValVersteegh, Marijn A. M.

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