Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:1811.01263 · Physical Review Applied

Practical Long-Distance Side-Channel-Free Quantum Key Distribution

Xiang‐Bin Wang, Xiao-Long Hu, Zong‐Wen Yu

Published Nov 14, 2019• 34 citations
arXivHTMLPDF

Abstract

Quantum key distribution (QKD) can provide secure communication even when an eavesdropper (the villainous ``Eve'') completely controls the channel. In practice, though, side-channel effects exist due to device imperfections, and Eve can still intercept information via a side channel. Thus the authors devise a QKD scheme that is both free of side channels in the source state and measurement-device-independent. While some other protocols can also achieve side-channel-free security, this one is based on mature technology without any demand for local detection efficiency, and works for distances greater than 200 km, even though the misalignment error rate may be as large as 20%.

DOI
10.1103/physrevapplied.12.054034

Related papers

Side-channel-free quantum key distribution with practical devices

Cong Jiang, Zong‐Wen Yu, Hu, Xiao-Long +1 more

Based on the idea that there is no side channel in the vacuum state, the side-channel-free quantum key distribution (SCFQKD) protocol was proposed, which is immune to all attacks in the source side-channel space and all attacks in the detectors. In the original SCFQKD protocol, an important assumption is that Alice and Bob can produce the perfect vacuum pulses. But due to the finite extinction ratio of the intensity modulators, the perfect vacuum pulse is impossible in practice. In this paper, we solve this problem and make the quantum key distribution side-channel secure with real source device which does not emit perfect vacuum pulses. Our conclusion only depends on the upper bounds of the intensities of the sources. No other assumptions such as stable sources and stable side channels are needed. The numerical results show that, comparing with the results of SCFQKD protocol with perfect vacuum sources, the key rates and secure distance are only slightly decreased if the upper bound of the intensity of the imperfect vacuum source is less than $10^{-8}$ which can be achieved in experiment by two-stage intensity modulator. We also show that the two-way classical communication can be used to the data post-processing of SCFQKD protocol to improve the key rate. Specially, the active odd-parity pairing method can improve the key rates in all distances by about two times and the secure distance by about 40 km. Give that the side channel security based on imperfect vacuum, this work makes it possible to realize side channel secure QKD with real devices.

arXiv:2205.08421•May 17, 2022•0 citations

Side-Channel-Secure Quantum Key Distribution with Imperfect Vacuum Sources

Cong Jiang, Zong‐Wen Yu, Xiao-Long Hu +1 more

The side-channel-secure (SCS) quantum key distribution (QKD), SCS QKD has attracted much attention due to its higher security compared to the measurement-device-independent protocols. It is not only measurement-device-independent secure, but also secure against source-state side channels provided that Eve has no access to Alice's or Bob's setups inside their labs. In the original protocol for SCS QKD, the side channels and the intensities of the coherent sources are allowed to be different in different time windows, but the vacuum sources of Alice and Bob have to be perfect, which is impossible in practice due to the finite extinction ratio of the intensity modulators. In this paper, we present a method that does not need the perfect vacuum source requested by the original protocol and assures the result as secure as the original protocol. With the upper bounds of the amplitudes of the nonvacuum part of the sources, the secure key rate of our SCS QKD protocol here with imperfect vacuum and unstable sources can be calculated. The numerical results show that, the secure distance of the SCS QKD protocol exceeds 150 km, provided that the intensity of the imperfect vacuum source is less than ${10}^{\ensuremath{-}8}$, which can be achieved in the experiment by a two-stage intensity modulator, where we also show that the active odd-parity pairing method and standard pairing method using two-way classical communication can be applied to the SCS QKD protocol to improve the key rate. Given the side-channel security based on the existing technological level, this work makes it possible to realize side-channel-secure QKD with real devices.

Physical Review Applied•Jun 1, 2023•11 citations

Experimental Side-Channel-Secure Quantum Key Distribution over 200 km

Zhou, Yang, Jing-Yang Liu, Chunhui Zhang +4 more

Quantum key distribution (QKD) enables two remote parties to share encryption keys with information-theoretic security guaranteed by physical laws. Side-channel-secure QKD (SCS-QKD) has attracted considerable attention because it simultaneously removes source and detector side-channel vulnerabilities. Although a recent experiment demonstrated SCS-QKD over 50 km, practical implementation remains challenging due to imperfect vacuum preparation and finite-key constraints under coherent attacks. Here, following the theoretical framework of Jiang et al. [Phys. Rev. Res. 6, 013266 (2024)], we experimentally implement a practical SCS-QKD protocol using an imperfect whole-space source and rigorous finite-key analysis. Benefiting from a stable GHz-level system operating at 1.25 GHz, we extend the transmission distance to 200 km and achieve high secure key rates of 18.31 kbps, 2.55 kbps, and 196.03 bps at 100 km, 150 km, and 200 km, respectively. Our results establish a new distance record for SCS-QKD and demonstrate the feasibility of high-speed, long-distance, and practically secure quantum key distribution.

arXiv:2505.03524•May 6, 2025•0 citations

Experimental side channel secure quantum key distribution under realistic conditions

Hao Dong, Cong Jiang, Di Ma +8 more

Quantum key distribution (QKD) theoretically provides unconditional security between remote parties. However, guaranteeing practical security through device characterization alone is challenging in real-world implementations due to the multidimensional spaces in which the devices may be operated. The side channel secure (SCS) QKD protocol, which only requires bounding the upper limits of the intensities for the two states, theoretically provides a rigorous solution to the challenge and achieves measurement-device-independent security in detection and security for whatever multidimensional side channel attack in the source. Here, we demonstrate a practical implementation of SCS-QKD, achieving a secure key rate of 6.67 kbps through a 50.5 km fiber and a maximum distribution distance of 101.1 km while accounting for finite-size effects. Our experiment also represents an approximately 40 times improvement over the previous experiment.

arXiv:2504.19242•Physical Review Research•Jan 23, 2026•2 citations

Proof-of-principle experimental demonstration of side-channel-secure quantum key distribution over 200 km

Yang Zhou, Jing-Yang Liu, Chun-Hui Zhang +4 more

Quantum key distribution (QKD) enables two remote parties to share encryption keys with information-theoretic security guaranteed by physical laws. Side-channel-secure QKD (SCS-QKD) has attracted considerable attention because it simultaneously removes source and detector side-channel vulnerabilities. Although a recent experiment demonstrated SCS-QKD over 50 km, practical implementation remains challenging due to imperfect vacuum preparation and finite-key constraints under coherent attacks. Here, following the theoretical framework of Jiang et al. [Phys. Rev. Res. 6, 013266 (2024)], we experimentally implement a practical SCS-QKD protocol using an imperfect whole-space source and rigorous finite-key analysis. Benefiting from a stable GHz-level system operating at 1.25 GHz, we extend the transmission distance to 200 km and achieve high secure key rates of 18.31 kbps, 2.55 kbps, and 196.03 bps at 100 km, 150 km, and 200 km, respectively. Our results establish a new distance record for SCS-QKD and demonstrate the feasibility of high-speed, long-distance, and practically secure quantum key distribution.

npj Quantum Information•Aug 11, 2026•0 citations

Bridging the gap between theory and practice in quantum cryptography

Marcos Curty, Kiyoshi Tamaki, Feihu Xu +4 more

Quantum key distribution (QKD) needs to close the big gap between theory and practice to be a suitable technology for achieving information-theoretic secure communications. Indeed, recent studies on side-channel attacks have exposed the vulnerabilities of QKD implementations against an eavesdropper who may try to attack both the source and the measurement device. Here, we review two potential approaches that, combined, could bring this goal closer: measurement-device-independent QKD and the loss-tolerant QKD protocol. The former removes all possible side-channels from the measurement apparatus and guarantees a high performance over long distances. The latter appears as a robust solution against typical source flaws and it offers similar key rates as those of standard QKD systems. Most importantly, the feasibility of both solutions has already been demonstrated in several lab and field-test experiments.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Oct 13, 2015•3 citations
Quantum key distribution (QKD) can provide secure communication even when an eavesdropper (the villainous ``Eve'') completely controls the channel. In practice, though, side-channel effects exist due to device imperfections, and Eve can still intercept information via a side channel. Thus the authors devise a QKD scheme that is both free of side channels in the source state and measurement-device-independent. While some other protocols can also achieve side-channel-free security, this one is based on mature technology without any demand for local detection efficiency, and works for distances greater than 200 km, even though the misalignment error rate may be as large as 20%.
Based on the idea that there is no side channel in the vacuum state, the side-channel-free quantum key distribution (SCFQKD) protocol was proposed, which is immune to all attacks in the source side-channel space and all attacks in the detectors. In the original SCFQKD protocol, an important assumption is that Alice and Bob can produce the perfect vacuum pulses. But due to the finite extinction ratio of the intensity modulators, the perfect vacuum pulse is impossible in practice. In this paper, we solve this problem and make the quantum key distribution side-channel secure with real source device which does not emit perfect vacuum pulses. Our conclusion only depends on the upper bounds of the intensities of the sources. No other assumptions such as stable sources and stable side channels are needed. The numerical results show that, comparing with the results of SCFQKD protocol with perfect vacuum sources, the key rates and secure distance are only slightly decreased if the upper bound of the intensity of the imperfect vacuum source is less than 10−810^{-8}10−8 which can be achieved in experiment by two-stage intensity modulator. We also show that the two-way classical communication can be used to the data post-processing of SCFQKD protocol to improve the key rate. Specially, the active odd-parity pairing method can improve the key rates in all distances by about two times and the secure distance by about 40 km. Give that the side channel security based on imperfect vacuum, this work makes it possible to realize side channel secure QKD with real devices.
The side-channel-secure (SCS) quantum key distribution (QKD), SCS QKD has attracted much attention due to its higher security compared to the measurement-device-independent protocols. It is not only measurement-device-independent secure, but also secure against source-state side channels provided that Eve has no access to Alice's or Bob's setups inside their labs. In the original protocol for SCS QKD, the side channels and the intensities of the coherent sources are allowed to be different in different time windows, but the vacuum sources of Alice and Bob have to be perfect, which is impossible in practice due to the finite extinction ratio of the intensity modulators. In this paper, we present a method that does not need the perfect vacuum source requested by the original protocol and assures the result as secure as the original protocol. With the upper bounds of the amplitudes of the nonvacuum part of the sources, the secure key rate of our SCS QKD protocol here with imperfect vacuum and unstable sources can be calculated. The numerical results show that, the secure distance of the SCS QKD protocol exceeds 150 km, provided that the intensity of the imperfect vacuum source is less than ${10}^{\ensuremath{-}8}$, which can be achieved in the experiment by a two-stage intensity modulator, where we also show that the active odd-parity pairing method and standard pairing method using two-way classical communication can be applied to the SCS QKD protocol to improve the key rate. Given the side-channel security based on the existing technological level, this work makes it possible to realize side-channel-secure QKD with real devices.
Quantum key distribution (QKD) enables two remote parties to share encryption keys with information-theoretic security guaranteed by physical laws. Side-channel-secure QKD (SCS-QKD) has attracted considerable attention because it simultaneously removes source and detector side-channel vulnerabilities. Although a recent experiment demonstrated SCS-QKD over 50 km, practical implementation remains challenging due to imperfect vacuum preparation and finite-key constraints under coherent attacks. Here, following the theoretical framework of Jiang et al. [Phys. Rev. Res. 6, 013266 (2024)], we experimentally implement a practical SCS-QKD protocol using an imperfect whole-space source and rigorous finite-key analysis. Benefiting from a stable GHz-level system operating at 1.25 GHz, we extend the transmission distance to 200 km and achieve high secure key rates of 18.31 kbps, 2.55 kbps, and 196.03 bps at 100 km, 150 km, and 200 km, respectively. Our results establish a new distance record for SCS-QKD and demonstrate the feasibility of high-speed, long-distance, and practically secure quantum key distribution.
Quantum key distribution (QKD) theoretically provides unconditional security between remote parties. However, guaranteeing practical security through device characterization alone is challenging in real-world implementations due to the multidimensional spaces in which the devices may be operated. The side channel secure (SCS) QKD protocol, which only requires bounding the upper limits of the intensities for the two states, theoretically provides a rigorous solution to the challenge and achieves measurement-device-independent security in detection and security for whatever multidimensional side channel attack in the source. Here, we demonstrate a practical implementation of SCS-QKD, achieving a secure key rate of 6.67 kbps through a 50.5 km fiber and a maximum distribution distance of 101.1 km while accounting for finite-size effects. Our experiment also represents an approximately 40 times improvement over the previous experiment.
Quantum key distribution (QKD) enables two remote parties to share encryption keys with information-theoretic security guaranteed by physical laws. Side-channel-secure QKD (SCS-QKD) has attracted considerable attention because it simultaneously removes source and detector side-channel vulnerabilities. Although a recent experiment demonstrated SCS-QKD over 50 km, practical implementation remains challenging due to imperfect vacuum preparation and finite-key constraints under coherent attacks. Here, following the theoretical framework of Jiang et al. [Phys. Rev. Res. 6, 013266 (2024)], we experimentally implement a practical SCS-QKD protocol using an imperfect whole-space source and rigorous finite-key analysis. Benefiting from a stable GHz-level system operating at 1.25 GHz, we extend the transmission distance to 200 km and achieve high secure key rates of 18.31 kbps, 2.55 kbps, and 196.03 bps at 100 km, 150 km, and 200 km, respectively. Our results establish a new distance record for SCS-QKD and demonstrate the feasibility of high-speed, long-distance, and practically secure quantum key distribution.
Quantum key distribution (QKD) needs to close the big gap between theory and practice to be a suitable technology for achieving information-theoretic secure communications. Indeed, recent studies on side-channel attacks have exposed the vulnerabilities of QKD implementations against an eavesdropper who may try to attack both the source and the measurement device. Here, we review two potential approaches that, combined, could bring this goal closer: measurement-device-independent QKD and the loss-tolerant QKD protocol. The former removes all possible side-channels from the measurement apparatus and guarantees a high performance over long distances. The latter appears as a robust solution against typical source flaws and it offers similar key rates as those of standard QKD systems. Most importantly, the feasibility of both solutions has already been demonstrated in several lab and field-test experiments.