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Physical Review Applied

Higher key rate in asymmetric quantum-classical integrated measurement-device-independent quantum-key-distribution systems

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

Published Nov 20, 2023• 9 citations
Publisher

Abstract

Integrating measurement-device-independent quantum key distribution (MDI QKD) with classical networks guarantees security and economy. Unfortunately, the performance of MDI QKD, suppressed though it is by network asymmetry, is further degraded by the addition of integration noise. As a consequence, symmetric systems are always believed to be better for a higher key rate. However, we reveal a counterintuitive fact that asymmetric MDI QKD has better performance in integrated systems. Modeling the mechanism of the asymmetric effect in integrated MDI systems and analyzing the noise-suppression effect of asymmetric structures, we observe an unanticipated increase of the key rate up to 260%, giving a conclusion diametrically opposite that for the original system. The phenomenon found and the proposed analytical model provide a method for noise suppression and performance improvement, permitting high adaptability for realistic asymmetric networks.

DOI
10.1103/physrevapplied.20.054042

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Integrating measurement-device-independent quantum key distribution (MDI QKD) with classical networks guarantees security and economy. Unfortunately, the performance of MDI QKD, suppressed though it is by network asymmetry, is further degraded by the addition of integration noise. As a consequence, symmetric systems are always believed to be better for a higher key rate. However, we reveal a counterintuitive fact that asymmetric MDI QKD has better performance in integrated systems. Modeling the mechanism of the asymmetric effect in integrated MDI systems and analyzing the noise-suppression effect of asymmetric structures, we observe an unanticipated increase of the key rate up to 260%, giving a conclusion diametrically opposite that for the original system. The phenomenon found and the proposed analytical model provide a method for noise suppression and performance improvement, permitting high adaptability for realistic asymmetric networks.
Measurement-device-independent quantum key distribution (MDI QKD), which eliminates all the attacks from the eavesdropper to the measurement party, has been one of the most promising technologies for the implementation of end-to-end quantum networks. In practice, the asymmetry of both sources and channels is generally inevitable. Therefore, we propose a theory to analyze the performance when any two MDI users in networks communicate using asymmetric sources in distinct single or multiple temporal modes. As a specific application, we model to obtain the key rate of MDI QKD with a weak-coherent pulse source and a spontaneous parametric down-conversion source, and compare the performance to the cases with symmetric (i.e., identical) sources. The result demonstrates that the actual performance does not degrade due to the asymmetry of sources. On the contrary, it maintains at a good level over the entire distance we study. This work provides a theoretical basis for analyzing and optimizing MDI-QKD networks with asymmetric sources, thus paving the way for the practical deployment of completely asymmetric MDI-QKD networks.
Measurement-device-independent quantum key distribution (MDI-QKD) completely closes the security loopholes caused by the imperfection of devices at the detection terminal. Commonly, a symmetric MDI-QKD model is widely used in simulations and experiments. This scenario is far from a real quantum network, where the losses of channels connecting each user are quite different. To adapt such a feature, an asymmetric MDI-QKD model is proposed. How to improve the performance of asymmetric MDI-QKD also becomes an important research direction. In this work, an advantage distillation (AD) method is applied to further improve the performance of asymmetric MDI-QKD without changing the original system structure. Simulation results show that the AD method can improve the secret key rate and transmission distance, especially in the highly asymmetric cases. Therefore, this scheme will greatly promote the development of future MDI-QKD networks.
Measurement-device-independent quantum key distribution (MDI-QKD) can eliminate all detector side channels and it is practical with current technology. Previous implementations of MDI-QKD all used two symmetric channels with similar losses. However, the secret key rate is severely limited when different channels have different losses. Here we report the results of the first high-rate MDI-QKD experiment over asymmetric channels. By using the recent 7-intensity optimization approach, we demonstrate>10×higher key rate than the previous best-known protocols for MDI-QKD in the situation of large channel asymmetry, and extend the secure transmission distance by more than 20-50 km in standard telecom fiber. The results have moved MDI-QKD towards widespread applications in practical network settings, where the channel losses are asymmetric and user nodes could be dynamically added or deleted.
Abstract Asymmetric measurement-device-independent quantum key distribution (MDI-QKD) enables building a scalable, high-rate quantum network with an untrusted relay in real-world scenarios. In this study, we improve the performance of asymmetric MDI-QKD using numerical analysis techniques. Simulation results show a twofold increase in tolerance to basis misalignment compared to the previous state-of-the-art method. Specifically, for instances of substantial basis misalignment, the key rate increases by an order of magnitude, and the maximum communication distance extends by 20 km. Our work significantly enhances the robustness and feasibility of asymmetric MDI-QKD, thereby promoting the widespread deployment of MDI-QKD networks.
Measurement-device-independent quantum key distribution (MDI-QKD) can eliminate detector side channels and prevent all attacks on detectors.The future of MDI-QKD is a quantum network that provides service to many users over untrusted relay nodes.In a real quantum network, the losses of various channels are different and users are added and deleted over time.To adapt to these features, we propose a type of protocol that allows users to independently choose their optimal intensity settings to compensate for different channel losses.Such a protocol enables a scalable high-rate MDI-QKD network that can easily be applied for channels of different losses and allows users to be dynamically added or deleted at any time without affecting the performance of existing users.
Measurement-device-independent quantum key distribution (MDI-QKD) is a promising path toward practical quantum communication, but current high-performance demonstrations come at prohibitive overhead and isolated environments. Here, we present a high-speed MDI-QKD system operating at an unprecedented repetition frequency of 2.5 GHz and verify its strong noise tolerance by incorporating the advantage distillation method. The secure key is efficiently generated under 425 kHz noise counts, which is 4 orders of magnitude higher than isolated systems. A secure key rate with a kbps level is achieved under 30 dB channel attenuation without bulky, resource-intensive detection devices. Our Letter establishes a complete practical solution for QKD deployment and resolves the persistent difficulty of realizing practical quantum secure networks with advanced security, a high key rate, environmental robustness, and physical compactness.