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Weerasinghe A, Alhussein M, Alderton A, Wonfor A, Penty R. Practical, high-speed Gaussian coherent state continuous variable quantum key distribution with real-time parameter monitoring, optimised slicing, and post-processed key distillation. Sci Rep 2023; 13:21543. [PMID: 38057348 DOI: 10.1038/s41598-023-47517-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Accepted: 11/14/2023] [Indexed: 12/08/2023] Open
Abstract
Gaussian coherent state continuous variable quantum key distribution has gained interest owing to its security and compatibility with classical coherent optical fibre networks. For successful system deployment it is necessary to implement practical high speed systems which distil keys efficiently. Here, we demonstrate a Gaussian coherent state continuous variable quantum key distribution system at a 50 MHz symbol rate. Unlike most demonstrations to date which measure excess noise and infer key rates from this, we record signals in real time and distil keys. We also demonstrate, for the first time, slice reconciliation with optimised guard bands to maximise achievable secret key rates. Using this optimisation with multilevel slicing, a record 5 Mb/s secret key rate after a transmission distance of 25 km is achieved. This is a significant improvement on the 3 Mb/s secret key rate which is achieved with single level optimised slice reconciliation.
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Affiliation(s)
- Amanda Weerasinghe
- Electrical Engineering Division, Department of Engineering, University of Cambridge, Cambridge, CB3 0FA, UK.
| | - Muataz Alhussein
- Electrical Engineering Division, Department of Engineering, University of Cambridge, Cambridge, CB3 0FA, UK
| | - Adam Alderton
- Electrical Engineering Division, Department of Engineering, University of Cambridge, Cambridge, CB3 0FA, UK
| | - Adrian Wonfor
- Electrical Engineering Division, Department of Engineering, University of Cambridge, Cambridge, CB3 0FA, UK.
| | - Richard Penty
- Electrical Engineering Division, Department of Engineering, University of Cambridge, Cambridge, CB3 0FA, UK
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Dong J, Wang T, He Z, Shi Y, Li L, Huang P, Zeng G. Effective Excess Noise Suppression in Continuous-Variable Quantum Key Distribution through Carrier Frequency Switching. ENTROPY (BASEL, SWITZERLAND) 2023; 25:1286. [PMID: 37761585 PMCID: PMC10527916 DOI: 10.3390/e25091286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Revised: 08/27/2023] [Accepted: 08/30/2023] [Indexed: 09/29/2023]
Abstract
Continuous-variable quantum key distribution (CV-QKD) is a promising protocol that can be easily integrated with classical optical communication systems. However, in the case of quantum-classical co-transmissions, such as dense wavelength division multiplexing with classical channels and time division multiplexing with large-power classical signal, a quantum signal is more susceptible to crosstalk caused by a classical signal, leading to signal distortion and key distribution performance reduction. To address this issue, we propose a noise-suppression scheme based on carrier frequency switching (CFS) that can effectively mitigate the influence of large-power random noise on the weak coherent state. In this noise-suppression scheme, a minimum-value window of the channel's noise power spectrum is searched for and the transmission signal frequency spectrum shifts to the corresponding frequency to avoid large-power channel noise. A digital filter is also utilized to filter out most of the channel noise. Simulation results show that compared to the traditional fixed carrier frequency scheme, the proposed noise-suppression scheme can reduce the excess noise to 1.8%, and the secret key rate can be increased by 1.43 to 2.86 times at different distances. This noise-suppression scheme is expected to be applied in scenarios like quantum-classical co-transmission and multi-QKD co-transmission to provide noise-suppression solutions.
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Affiliation(s)
- Jing Dong
- State Key Laboratory of Advanced Optical Communication Systems and Networks, Center of Quantum Sensing and Information Processing, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Tao Wang
- State Key Laboratory of Advanced Optical Communication Systems and Networks, Center of Quantum Sensing and Information Processing, Shanghai Jiao Tong University, Shanghai 200240, China
- Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
| | - Zhuxuan He
- State Key Laboratory of Advanced Optical Communication Systems and Networks, Center of Quantum Sensing and Information Processing, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Yueer Shi
- State Key Laboratory of Advanced Optical Communication Systems and Networks, Center of Quantum Sensing and Information Processing, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Lang Li
- State Key Laboratory of Advanced Optical Communication Systems and Networks, Center of Quantum Sensing and Information Processing, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Peng Huang
- State Key Laboratory of Advanced Optical Communication Systems and Networks, Center of Quantum Sensing and Information Processing, Shanghai Jiao Tong University, Shanghai 200240, China
- Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
| | - Guihua Zeng
- State Key Laboratory of Advanced Optical Communication Systems and Networks, Center of Quantum Sensing and Information Processing, Shanghai Jiao Tong University, Shanghai 200240, China
- Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
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Gong Y, Wonfor A, Hunt JH, White IH, Penty RV. Experimental demonstration of confidential communication with quantum security monitoring. Sci Rep 2021; 11:21686. [PMID: 34737374 PMCID: PMC8569167 DOI: 10.1038/s41598-021-01013-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2021] [Accepted: 09/29/2021] [Indexed: 12/05/2022] Open
Abstract
Security issues and attack management of optical communication have come increasingly important. Quantum techniques are explored to secure or protect classical communication. In this paper, we present a method for in-service optical physical layer security monitoring that has vacuum-noise level sensitivity without classical security loopholes. This quantum-based method of eavesdropping detection, similar to that used in conventional pilot tone systems, is achieved by sending quantum signals, here comprised of continuous variable quantum states, i.e. weak coherent states modulated at the quantum level. An experimental demonstration of attack detection using the technique was presented for an ideal fibre tapping attack that taps 1% of the ongoing light in a 10 dB channel, and also an ideal correlated jamming attack in the same channel that maintains the light power with excess noise increased by 0.5 shot noise unit. The quantum monitoring system monitors suspicious changes in the quantum signal with the help of advanced data processing algorithms. In addition, unlike the CV-QKD system which is very sensitive to channel excess noise and receiver system noise, the quantum monitoring is potentially more compatible with current optical infrastructure, as it lowers the system requirements and potentially allows much higher classical data rate communication with links length up to 100 s km.
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Affiliation(s)
- Yupeng Gong
- Electrical Engineering Division, University of Cambridge, 9 JJ Thomson Ave, Cambridge, CB3 0FA, UK.
| | - Adrian Wonfor
- Electrical Engineering Division, University of Cambridge, 9 JJ Thomson Ave, Cambridge, CB3 0FA, UK
| | | | - Ian H White
- Electrical Engineering Division, University of Cambridge, 9 JJ Thomson Ave, Cambridge, CB3 0FA, UK
- University of Bath, Claverton Down, Bath, BA2 7AY, UK
| | - Richard V Penty
- Electrical Engineering Division, University of Cambridge, 9 JJ Thomson Ave, Cambridge, CB3 0FA, UK
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Gong Y, Kumar R, Wonfor A, Ren S, Penty RV, White IH. Secure optical communication using a quantum alarm. LIGHT, SCIENCE & APPLICATIONS 2020; 9:170. [PMID: 33082939 PMCID: PMC7532184 DOI: 10.1038/s41377-020-00409-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/01/2020] [Revised: 09/07/2020] [Accepted: 09/21/2020] [Indexed: 06/11/2023]
Abstract
Optical fibre networks are advancing rapidly to meet growing traffic demands. Security issues, including attack management, have become increasingly important for optical communication networks because of the vulnerabilities associated with tapping light from optical fibre links. Physical layer security often requires restricting access to channels and periodic inspections of link performance. In this paper, we report how quantum communication techniques can be utilized to detect a physical layer attack. We present an efficient method for monitoring the physical layer security of a high-data-rate classical optical communication network using a modulated continuous-variable quantum signal. We describe the theoretical and experimental underpinnings of this monitoring system and the monitoring accuracy for different monitored parameters. We analyse its performance for both unamplified and amplified optical links. The technique represents a novel approach for applying quantum signal processing to practical optical communication networks and compares well with classical monitoring methods. We conclude by discussing the challenges facing its practical application, its differences with respect to existing quantum key distribution methods, and its usage in future secure optical transport network planning.
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Affiliation(s)
- Yupeng Gong
- Centre for Advanced Photonics and Electronics, University of Cambridge, 9 JJ Thomson Ave, Cambridge, CB3 0FA UK
| | - Rupesh Kumar
- Quantum Communications Hub, Information Centre, Department of Physics, University of York, York, YO10 5DD UK
| | - Adrian Wonfor
- Centre for Advanced Photonics and Electronics, University of Cambridge, 9 JJ Thomson Ave, Cambridge, CB3 0FA UK
| | - Shengjun Ren
- Centre for Advanced Photonics and Electronics, University of Cambridge, 9 JJ Thomson Ave, Cambridge, CB3 0FA UK
| | - Richard V. Penty
- Centre for Advanced Photonics and Electronics, University of Cambridge, 9 JJ Thomson Ave, Cambridge, CB3 0FA UK
| | - Ian H. White
- Centre for Advanced Photonics and Electronics, University of Cambridge, 9 JJ Thomson Ave, Cambridge, CB3 0FA UK
- University of Bath, Claverton Down, Bath, BA2 7AY UK
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