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Physical Review A

Dependency model for high-performance quantum-key-distribution systems

Xiaojuan Huang, Feng-Yu Lu, Shuang Wang, Zhen−Qiang Yin, Ze-Hao Wang, Wei Chen, De‐Yong He, Guan‐Jie Fan‐Yuan, Guang‐Can Guo, Zheng‐Fu Han

Published Dec 7, 2022• 9 citations
Publisher

Abstract

A precise estimation of the detection response is essential for a high-performance and secure quantum-key-distribution (QKD) system. Single-photon avalanche diodes (SPADs) are widely applied to estimate the single-photon yields. However, in the presence of the dead time and afterpulse of the SPADs, the estimations of gains in previous models are biased, which will lead to ill-fitting optimized parameters and greatly degrade the system performance. Here, we develop a dependency model for providing more accurate optimization to achieve higher-performance QKD systems. Moreover, to further improve the system performance, our model guides users to choose proper dead time. Our simulation results indicate that our model plays an important role in the practical application and deployment of QKD systems.

DOI
10.1103/physreva.106.062607

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A precise estimation of the detection response is essential for a high-performance and secure quantum-key-distribution (QKD) system. Single-photon avalanche diodes (SPADs) are widely applied to estimate the single-photon yields. However, in the presence of the dead time and afterpulse of the SPADs, the estimations of gains in previous models are biased, which will lead to ill-fitting optimized parameters and greatly degrade the system performance. Here, we develop a dependency model for providing more accurate optimization to achieve higher-performance QKD systems. Moreover, to further improve the system performance, our model guides users to choose proper dead time. Our simulation results indicate that our model plays an important role in the practical application and deployment of QKD systems.
In light of the growing widely utilized single-photon avalanche detectors, dead time is inevitable due to the presence of afterpulse. Dead time is a critical factor that influences the count rate and the secret key rate (SKR) of quantum key distribution (QKD). It is particularly significant in time-bin-encoding systems, while prior models fail to accurately estimate the gains. Of note, it introduces correlations between early bins and late bins, hence bits with strong correlation and security risks. Here, we put forward a realistic model that precisely characterizes the response of detectors for time-bin-encoding systems. Our model not only improves the accuracy of gain predictions, showing an excellent match with the Monte Carlo simulation results, but also provides theoretical support for data processing, helping to mitigate security risks. Finally, leveraging our model, we can get a much higher SKR than prior models and further enhance the performance of practical QKD systems by adjusting the detector parameters. Our simulation results demonstrate that our model is essential for the application and deployment of QKD systems in practice.
InGaAs/InP single-photon avalanche diodes (SPADs) are widely used in practical applications requiring near-infrared photon counting such as quantum key distribution (QKD). Photon detection efficiency and dark count rate are the intrinsic parameters of InGaAs/InP SPADs, due to the fact that their performances cannot be improved using different quenching electronics given the same operation conditions. After modeling these parameters and developing a simulation platform for InGaAs/InP SPADs, we investigate the semiconductor structure design and optimization. The parameters of photon detection efficiency and dark count rate highly depend on the variables of absorption layer thickness, multiplication layer thickness, excess bias voltage, and temperature. By evaluating the decoy-state QKD performance, the variables for SPAD design and operation can be globally optimized. Such optimization from the perspective of specific applications can provide an effective approach to design high-performance InGaAs/InP SPADs.
Recently, there has been growing research interest in quantum technology in general and particularly in quantum key distribution (QKD) that enables two legitimate parties to share a secret key without leaking information to third parties. Practical implementation of QKD has shown limited key rates due to the practical limits of quantum sources and detectors. For example, after each detection event, practical single-photon detectors such as single-photon avalanche diodes (SPADs) undergo a period of inactivity called dead time, which limits the highest photon transmission rate achievable for QKD systems as photon transmission at sub-dead-time regime can generate security loopholes. In this paper, we analyze the performance of a sifting scheme that allows for high-speed operation at sub-dead-time regime both theoretically and numerically. We consider an FSO QKD system, where the effect of background noise can be significant and derive the expressions of sifting probability and sifted bit rate considering both dead time and background noise effects. We present a comprehensive performance analysis of the QKD system in terms of quantum bit error rate (QBER) and secrecy key rate (SKR) and show that operation at sub-dead-time regime can significantly improve the achievable SKR for FSO systems with certain path loss and background noise levels.
Quantum key distribution (QKD) networks can provide unconditional secure communications among many remote users. In real QKD networks, with the dynamic access and quit of nodes, qualities of various user links and the link lengths among different users, such as transmission loss, are different and changing. Customized optimization that aims at various channel environments offers a network performance benefit. In this paper, we propose including the detection efficiency, dark-count probability, and afterpulse rate of the single-photon avalanche photodiode (SPAD) into the parameter optimization by controlling its voltage and temperature to optimize the secure key rates in dynamic QKD networks. The result shows that our method improves the network adaptability to the variation and asymmetry of channel and profits the establishment of QKD networks in a complex channel environment. This method is suitable for arbitrary SPAD-based QKD system and network architecture.
Abstract The safe exchange of cryptographic keys is made possible by Quantum Key Distribution (QKD), which makes use of the basic ideas of quantum physics. Quantum Bit Error Rate (QBER), key generation rate, and transmission distance are important performance measures in QKD systems. Nevertheless, undesired noise sources that impair system performance, such dark counts and afterpulses, restrict traditional QKD implementations. The Measurement-Device-Independent QKD (MDI-QKD) protocol and Single Photon Avalanche Diodes (SPADs) for single-photon detection are combined in this research to create an improved QKD model. All detector-side-channel weaknesses are naturally eliminated by the MDI-QKD protocol, while SPADs' excellent sensitivity and temporal precision allow for precise noise source detection and characterisation, including dark count and afterpulse rates. When compared to conventional QKD systems, the suggested method performs better when assessed using QBER. According to experimental findings, including SPADs into the MDI-QKD architecture greatly improves the security and effectiveness of quantum communication systems by detecting detector-induced errors.
Single-photon detection concept is the most crucial factor that determines the performance of quantum key distribution (QKD) systems. In this paper, a simulator with time domain visualizers and configurable parameters using continuous time simulation approach is presented for modeling and investigating the performance of single-photon detectors operating in Gieger mode at the wavelength of 830 nm. The widely used C30921S silicon avalanche photodiode was modeled in terms of avalanche pulse, the effect of experiment conditions such as excess voltage, temperature and average photon number on the photon detection efficiency, dark count rate and afterpulse probability. This work shows a general repeatable modeling process for significant performance evaluation. The most remarkable result emerged from the simulated data generated and detected by commercial devices is that the modeling process provides guidance for single-photon detectors design and characterization. The validation and testing results of the single-photon avalanche detectors (SPAD) simulator showed acceptable results with the theoretical and experimental results reported in related references and the device's data sheets.