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Experimental multiuser secure quantum communications
Stockholm University, Faculty of Science, Department of Physics. (KOF)
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

We are currently experiencing a rapid development of quantum information, a new branch of science, being an interdisciplinary of quantum physics, information theory, telecommunications, computer science, and many others. This new science branch was born in the middle of the eighties, developed rapidly during the nineties, and in the current decade has brought a technological breakthrough in creating secure quantum key distribution (QKD), quantum secret sharing, and exciting promises in diverse technological fields. Recent QKD experiments have achieved high rate QKD at 200 km distance in optical fiber. Significant QKD results have also been achieved in free-space.

Due to the rapid broadband access deployment in many industrialized countries and the standing increasing transmission security treats, the natural development awaiting quantum communications, being a part of quantum information, is its migration into commercial switched telecom networks. Such a migration concerns both multiuser quantum key distribution and multiparty quantum secret sharing that have been the main goal of my PhD studies. They are also the main concern of the thesis.

Our research efforts in multiuser QKD has led to a development of the five-user setup for transmissions over switched fiber networks in a star and in a tree configuration. We have achieved longer secure quantum information distances and implemented more nodes than other multi-user QKD experiments. The measurements have shown feasibility of multiuser QKD over switched fiber networks, using standard fiber telecom components.

Since circular architecture networks are important parts of both intranets and the Internet, Sagnac QKD has also been a subject of our research efforts. The published experiments in this area have been very few and results were not encouraging, mainly due to the single mode fiber (SMF) birefringence. Our research has led to a development of a computer controlled birefringence compensation in Sagnac that open the door to both classical and quantum Sagnac applications. On the quantum secret sharing side, we have achieved the first quantum secret sharing experiment over telecom fiber in a five-party implementation using the "plug & play" setup and in a four-party implementation using Sagnac configuration. The setup measurements have shown feasibility and scalability of multiparty quantum communication over commercial telecom fiber networks.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University , 2009. , 110 p.
Keyword [en]
Quantum key distribution, multiparty quantum secret sharing, Sagnac interferometer, “plug & play” QKD, Passive Optical Network (PON), decoy states, single mode fiber birefringence compensation, quantum bit error rate, visibility
National Category
Physical Sciences
Research subject
Physics
Identifiers
URN: urn:nbn:se:su:diva-26498ISBN: 978-91-7155-846-6 (print)OAI: oai:DiVA.org:su-26498DiVA: diva2:210124
Public defence
2009-04-27, AlbaNova FB42, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2009-04-06 Created: 2009-03-30 Last updated: 2009-04-01Bibliographically approved
List of papers
1. Experimental quantum secret sharing using telecommunication fiber
Open this publication in new window or tab >>Experimental quantum secret sharing using telecommunication fiber
2008 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, Vol. 78, no 6Article in journal (Refereed) Published
Abstract

We report quantum secret sharing experiment in telecommunication fiber in five-party implementation. The quantum secret sharing experiment has been based on a single qubit protocol, which has opened the door to practical secret sharing implementation over fiber channels and in free space. The previous quantum secret sharing proposals were based on multiparticle entangled states, difficult in the practical implementation and not scalable. The secret sharing protocol has been implemented in an interferometric fiber optics setup with phase encoding and demonstrated for three, four, and five parties. The experimental setup measurements have shown feasibility and scalability of secure multiparty quantum communication over commercial telecom fiber networks.

Identifiers
urn:nbn:se:su:diva-26531 (URN)10.1103/PhysRevA.78.062307 (DOI)000262242400047 ()
Note
Artikeln är på 6 sidor.Available from: 2009-04-01 Created: 2009-04-01 Last updated: 2009-04-02Bibliographically approved
2. Multiuser quantum key distribution over telecom fiber networks
Open this publication in new window or tab >>Multiuser quantum key distribution over telecom fiber networks
2009 (English)In: Optics Communications, ISSN 0030-4018, Vol. 282, no 2, 258-262 p.Article in journal (Refereed) Published
Abstract [en]

We report five-user quantum key distribution (QKD) over switched fiber networks in both star and tree configurations, using the BB84-protocol [1] with phase encoding. Both setups implement polarization insensitive phase modulators, necessary for birefringent single mode fiber (SMF) networks. In both configurations we have achieved transmission distances between 25 km and 50 km with quantum bit error rates between 1.24% and 5.56% for the mean photon number l ¼ 0:1. The measurements have showed feasibility of multiuser QKD over switched fiber networks, using standard fiber telecom components.

Identifiers
urn:nbn:se:su:diva-26534 (URN)10.1016/j.optcom.2008.10.030 (DOI)000261852400018 ()
Available from: 2009-04-01 Created: 2009-04-01 Last updated: 2009-04-03Bibliographically approved
3. Sagnac quantum key distribution over telecom fiber networks
Open this publication in new window or tab >>Sagnac quantum key distribution over telecom fiber networks
2009 (English)In: Optics Communications, ISSN 0030-4018, Vol. 282, no 6, 1231-1236 p.Article in journal (Refereed) Published
Abstract [en]

We present a new concept for compensation of single mode fiber (SMF) birefringence effects in a Sagnac quantum key distribution (QKD) setup, based on a polarization control system and a polarization insensitive phase modulator. Our experimental data show stable (in regards to birefringence drift) QKD over 1550 nm SMF telecom networks in Sagnac configuration, using the BB84-protocol [C.H. Bennett, G. Brassard, in: Proceedings of the IEEE International Conference on Computers, Systems, and Signal Processing, Institute of Electrical and Electronic Engineers, New York, 1984, p. 175] with phase encoding. The achieved total Sagnac transmission loop distances were between 100 km and 150 km with quantum bit error rates (QBER) between 5.84% and 9.79% for the mean-photon-number l = 0.1. The distances were much longer and rates much higher than in any other published Sagnac QKD experiments. We also show an example of our one-decoy state protocol implementations (for the 45 km distance between Alice and Bob, corresponding to the 130 km total Sagnac loop length), providing an unconditional QKD security. The measurement results have showed feasibility of QKD over telecom fiber networks in Sagnac configuration, using standard fiber telecom components.

Identifiers
urn:nbn:se:su:diva-26537 (URN)10.1016/j.optcom.2008.12.023 (DOI)000263635100032 ()
Available from: 2009-04-01 Created: 2009-04-01 Last updated: 2009-04-02Bibliographically approved
4. Sagnac secret sharing over telecom fiber networks
Open this publication in new window or tab >>Sagnac secret sharing over telecom fiber networks
2009 (English)In: Optics Express, ISSN 1094-4087, Vol. 17, no 2, 1055-1063 p.Article in journal (Refereed) Published
Abstract [en]

We report the first Sagnac quantum secret sharing (in threeand four-party implementations) over 1550 nm single mode fiber (SMF) networks, using a single qubit protocol with phase encoding. Our secret sharing experiment has been based on a single qubit protocol, which has opened the door to practical secret sharing implementation over fiber telecom channels and in free-space. The previous quantum secret sharing proposals were based on multiparticle entangled states, difficult in the practical implementation and not scalable. Our experimental data in the three-party implementation show stable (in regards to birefringence drift) quantum secret sharing transmissions at the total Sagnac transmission loop distances of 55-75 km with the quantum bit error rates (QBER) of 2.3-2.4% for the mean photon number μ = 0.1 and 1.7-2.1% for μ = 0.3. In the four-party case we have achieved quantum secret sharing transmissions at the total Sagnac transmission loop distances of 45-55 km with the quantum bit error rates (QBER) of 3.0-3.7% for the mean photon number μ = 0.1 and 1.8-3.0% for μ = 0.3. The stability of quantum transmission has been achieved thanks to our new concept for compensation of SMF birefringence effects in Sagnac, based on a polarization control system and a polarization insensitive phase modulator. The measurement results have showed feasibility of quantum secret sharing over telecom fiber networks in Sagnac configuration, using standard fiber telecom components.

Identifiers
urn:nbn:se:su:diva-26538 (URN)10.1364/OE.17.001055 (DOI)000263432300074 ()
Available from: 2009-04-01 Created: 2009-04-01 Last updated: 2009-04-02Bibliographically approved
5. Single mode fiber birefringence compensation in Sagnac and "plug & play" interferometric setups
Open this publication in new window or tab >>Single mode fiber birefringence compensation in Sagnac and "plug & play" interferometric setups
2009 (English)In: Optics Express, ISSN 1094-4087, Vol. 17, no 6, 4485-4494 p.Article in journal (Refereed) Published
Abstract [en]

Single mode fiber (SMF) birefringence effects have been a limiting factor for a variety of Sagnac applications over longer distance SMF links. In this report, we present a new concept of the SMF birefringence compensation in a Sagnac interferometric setup, based on a novel polarization control system. For the destructive interference, our control system guarantees a perfect compensation of both the SMF birefringence and imperfect propagation times matching of the setup’s components. For the stabilization of the constructive interference, we have applied a fiber stretcher and a simple proportional−integral−derivative (PID) controller. The enclosed experimental data of the setup’s visibility confirm validity of our polarization control system. We have also showed that the SMF birefringence model used in a “plug & play” interferometric setup [19], widely cited in the papers on quantum key distribution [11, 12, 13], cannot be applied in SMF Sagnac interferometric setup. However, the SMF birefringence model based on the Kapron equivalence well describes SMF Sagnac.

Identifiers
urn:nbn:se:su:diva-26542 (URN)10.1364/OE.17.004485 (DOI)000264747300030 ()
Available from: 2009-04-01 Created: 2009-04-01 Last updated: 2009-04-02Bibliographically approved

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