Dokument: Long distance quantum key distribution with quantum repeaters
| Titel: | Long distance quantum key distribution with quantum repeaters | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=30272 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20140818-112405-6 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Englisch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | M.Sc. Abruzzo, Silvestre [Autor] | |||||||
| Dateien: |
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| Beitragender: | Prof. Dr. Bruß, Dagmar [Betreuer/Doktorvater] | |||||||
| Stichwörter: | quantum repeaters, quantum key distribution, quantum cryptography | |||||||
| Dewey Dezimal-Klassifikation: | 500 Naturwissenschaften und Mathematik » 530 Physik | |||||||
| Beschreibung: | Quantum cryptography, or more precisely, quantum key distribution (QKD) allows two parties to share a secret key which can be used for symmetric-key cryptography. The advantage to use quantum states over classical bits is that they permit to catch a possible eavesdropper who tries to acquire information about the secret key. Therefore, QKD has attracted a lot of attention in recent years. After the initial developments and experimental realizations there are now very complex protocols and quantum devices to realize such protocols. However, it would be desirable to enable quantum key distribution over large distances, i.e. continental and intercontinental distances. For this purpose quantum repeaters have been proposed. These are protocols which exploit entanglement and quantum information primitives as entanglement swapping and entanglement distillation.
The final aim is to create a long-distance entangled pair. This pair may be then used for quantum key distribution. Although quantum repeaters have been proposed 15 years ago, the analysis of their requirements and performance in connection to QKD is still in its infancy. In this dissertation we give first a short presentation of quantum key distribution and quantum repeaters. Then we discuss our results. In order to study the efficiency of a quantum repeater we consider the secret key rate, and for analyzing minimal requirements we calculate the threshold quantum bit error rate, which represents the maximal noise that is compatible with the generation of a secret key. We start our analysis by describing the requirements and the performance of three important quantum repeater protocols, namely the original quantum repeater, the hybrid quantum repeater and the quantum repeater based on linear optics and atomic ensembles. Then we optimize the quantum repeater protocols and we find the trade-off between the amount of entanglement distillation and entanglement swapping as a function of the quantum device parameters.After this general investigation, we concetrate on protocols which may be realized in the near future, i.e. protocols with only one repeater station. Such protocols, when considered without quantum memories are called measurement-device independent QKD. This kind of protocols have attracted considerable attention in the last two years both from the experimental and theoretical side. In this thesis we have generalized such protocols to the scenario where there are quantum memories. We have proven that even when quantum memories are imperfect it is possible to improve over protocols with quantum memories. Then we have considered scenarios where in the quantum repeater there are many quantum memories and we have studied the performance of multiplexing. We have introduced the concept of finite-range multiplexing and we have shown that finite-range connections are sufficient in order to have most of the advantage of full-range multiplexing. Finally we have considered finite-key corrections for the six-state protocol when common imperfections are considered. The result of this work can be used as a basis for future study of finite-key corrections in protocols with quantum repeaters. The results of this dissertation clarify the role of imperfections in quantum repeaters when used for quantum key distribution. Our calculation of the minimal requirements help experimental groups to concentrate their effort on proper figure of merits. On the other side, our study on quantum repeaters with two segments are promising to beat in the near-future long distance QKD without quantum repeaters. | |||||||
| Lizenz: |  Urheberrechtsschutz | |||||||
| Fachbereich / Einrichtung: | Mathematisch- Naturwissenschaftliche Fakultät » WE Physik » Theoretische Physik | |||||||
| Dokument erstellt am: | 18.08.2014 | |||||||
| Dateien geändert am: | 18.08.2014 | |||||||
| Promotionsantrag am: | 05.11.2013 | |||||||
| Datum der Promotion: | 16.01.2014 |
