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Twin-field quantum key distribution network system
| DC Field | Value | Language |
|---|---|---|
| dc.contributor.advisor | 김상인 | - |
| dc.contributor.author | 박창훈 | - |
| dc.date.accessioned | 2022-11-29T03:01:15Z | - |
| dc.date.available | 2022-11-29T03:01:15Z | - |
| dc.date.issued | 2022-08 | - |
| dc.identifier.other | 32048 | - |
| dc.identifier.uri | https://dspace.ajou.ac.kr/handle/2018.oak/20935 | - |
| dc.description | 학위논문(박사)--아주대학교 일반대학원 :전자공학과,2022. 8 | - |
| dc.description.abstract | 양자 암호 시스템, 특히 QKD(quantum key distribution)는 양자 컴퓨터에 대한 물리적인 보안성을 제공할 방법으로 크게 주목받고 있다. 최근의 QKD에 관한 연구는 통신 거리와 네트워크 확장 연구를 통한 실제의 양자암호 통신망 구축을 지향하고 있다. 4,600km의 양자 네트워크 구축사례와 현존 최장 거리 프로토콜로 평가받는 TF-QKD(twin-field QKD)의 500km 실 환경 검증사례 등을 고려하면, 거리 확장과 네트워크 운용 각각에 관한 연구는 순조롭게 진행되고 있는 것으로 보인다. 하지만, 둘이 결합한 형태, 즉 TF-QKD 네트워크에 관한 연구는 링 네트워크 구조에 대해서만 10km 광섬유를 활용한 실험실 검증이 이루어진 상태로 아직 미진한 상황이다. 본 논문에서는 Sagnac interferometer 기반의 PnP(plug-and-play) 구조를 적용하여 TF-QKD 구현의 주요 장애물이었던 광 모드매칭 문제를 실용적으로 해결하고 더 나아가 2×N 네트워크까지 확장할 수 있게 하는 새로운 TF-QKD 네트워크 구조를 제안한다. 제안하는 네트워크 구조는 PnP 구조에 기반하여 일반적인 TF-QKD 네트워크 구조보다 더 적은 수의 제어장치들로 구현될 수 있기 때문에 구현이 실용적이며, 한 쌍의 단일 광자 검출기로 전체 네트워크 시스템을 구동할 수 있는 구조가 적용되어 구현 비용 절감의 장점도 가지고 있다. 또한, 실험실 환경에서 50km 광섬유를 사용하여 제안하는 구조를 구현하였으며, 펄스 당 1.31×10-4비트(초당 1.52비트)라는 타당한 수준의 비밀키 생성률을 달성하여 제안하는 구조의 구현 가능성을 증명했다. | - |
| dc.description.tableofcontents | 1 Introduction 1 1.1 Quantum key distribution (QKD) 1 1.2 QKD protocols 2 1.2.1 BB84 protocol 2 1.2.2 Measurement-device-independent QKD (MDI-QKD) 6 1.2.3 Twin-field QKD (TF-QKD) 9 1.3 Challenges in QKD implementation 13 1.3.1 Communication distance 13 1.3.2 Network 14 1.3.3 System stabilization 14 1.3.4 Hacking 15 1.4 Outline of the thesis 19 2 QKD implementation 21 2.1 Plug-and-play (PnP) architecture 21 2.2 PnP MDI-QKD 24 2.2.1 Architecture 25 2.2.2 Polarization-division multiplexing 28 2.2.3 Mach–Zehnder interferometer issue 29 2.2.4 Timing calibration 30 2.2.5 Experimental results 32 2.3 Implementation of transmitter in PnP QKDs 33 2.3.1 Polarization independent phase modulator (PM) 34 2.3.2 Polarization independent intensity modulator (IM) 35 2.3.3 IM auto bias control method 36 3 TF-QKD network architecture 44 3.1 2×N PnP TF-QKD network 44 3.1.1 Architecture 46 3.1.2 Operation principle 49 3.2 TF-QKD protocols 51 3.2.1 Phase-matching QKD 51 3.2.2 No phase post-selection TF-QKD 52 3.2.3 Sending or not-sending TF-QKD 53 3.2.4 Comparison 56 4 Experiments 57 4.1 Setup 57 4.1.1 Experimental setup 57 4.1.2 Phase post-compensation method 59 4.1.3 Polarization independent PM/IM 61 4.1.4 IM auto bias control method 62 4.1.5 Timing calibration 62 4.2 Results 63 4.2.1 Demonstration of the system stability 63 4.2.2 Secret key rate with the finite-size effect 64 5 Conclusion and Future works 68 5.1 Conclusion 68 5.2 Future works 70 Appendix A: Bell state measurement 71 Appendix B: Decoy-state method analysis 82 Appendix C: Finite-size effect analysis 84 References 87 | - |
| dc.language.iso | eng | - |
| dc.publisher | The Graduate School, Ajou University | - |
| dc.rights | 아주대학교 논문은 저작권에 의해 보호받습니다. | - |
| dc.title | Twin-field quantum key distribution network system | - |
| dc.type | Thesis | - |
| dc.contributor.affiliation | 아주대학교 일반대학원 | - |
| dc.contributor.department | 일반대학원 전자공학과 | - |
| dc.date.awarded | 2022. 8 | - |
| dc.description.degree | Doctoral | - |
| dc.identifier.localId | 1254168 | - |
| dc.identifier.uci | I804:41038-000000032048 | - |
| dc.identifier.url | https://dcoll.ajou.ac.kr/dcollection/common/orgView/000000032048 | - |
| dc.subject.keyword | network | - |
| dc.subject.keyword | quantum cryptography | - |
| dc.subject.keyword | quantum key distribution | - |
| dc.subject.keyword | twin field | - |
| dc.description.alternativeAbstract | Quantum cryptosystem, in particular, quantum key distribution (QKD), provides physically-guaranteed security against quantum computers, thus attracting significant attention. The recent studies of QKD have directed toward beating distance limits and network expansion for implementing real-world quantum cryptosystems. Considering the remarkable report on a quantum communication network spanning over 4,600 km, it seems that QKD networks using conventional protocols have been sufficiently studied. However, twin-field QKD (TF-QKD) networks have been researched only for a ring-type network over a 10-km fiber in a laboratory, although a point-to-point TF-QKD has been studied enough to succeed in field demonstrations over 428- and 511-km fiber. In this thesis, we propose a star-type 2×N TF-QKD network scheme, where the coherence maintenance, being the primary challenge to TF-QKD implementation, can be easily achieved by a mode-matching advantage of the Sagnac-based plug-and-play (PnP) architecture. Due to the PnP architecture, implementing the proposed network scheme requires fewer active controllers in comparison with building a network comprising one-way TF-QKDs. Moreover, a cost-effective configuration that allows the entire network system to operate with only a single pair of single-photon detectors is applied. We present an experimental proof-of-principle demonstration over a 50-km fiber in a laboratory, obtaining 1.31×10-4 bit per pulse (1.52 bit per second) as an average secret key rate with the finite-size effect. We organized the contents as follows. In Chapter 1, we introduce the background information on QKD including implementation challenges. In Chapter 2, we present the core techniques for implementing the proposed TF-QKD network. Besides, we report the corresponding experimental demonstrations. In Chapter 3, we propose a new TF-QKD network scheme. Moreover, we describe several variants of TF-QKD and explain why we choose a sending or not-sending TF-QKD protocol for our experiment via comparison of the variants. In Chapter 4, we show the experimental setup and result. In addition, we explain how to stabilize the experimental setup. In Chapter 5, we conclude our works and discuss future works. | - |
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