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

Physical Review Letters

Experimental Measurement-Device-Independent Quantum Conference Key Agreement

Kui-Xing Yang, Ya-Li Mao, Hu Chen, Xiduo Dong, Jiankun Zhu, Jizhou Wu, Zheng-Da Li

Published Nov 20, 2024• 19 citations
Publisher

Abstract

Quantum networks aim to enable quantum information tasks among multiple parties. Quantum conference key agreement (QCKA) is a typical task in quantum networks, which distributes information-theoretically secure keys among multiple users. However, QCKA relying on directly distributing Greenberger-Horne-Zeilinger (GHZ) states over long distances faces significant challenges due to the fragility of these states. Measurement-device-independent QCKA (MDI-QCKA) based on distributing the postselected GHZ entanglement can address this issue and eliminate all loopholes in detection side channels. Here, by developing three-photon GHZ interference technology with high visibility among three independent coherent sources, we realized the first MDI-QCKA experiment over a 60 km fiber link, achieving a secret key rate of 45.5 bits/s. Our result represents a significant step towards practical long-distance QCKA using realistic devices. Moreover, the technology we developed opens the way to future multiparty quantum communications in quantum networks.

DOI
10.1103/physrevlett.133.210803

Related papers

Repeater-like asynchronous measurement-device-independent quantum conference key agreement

Yu-Shuo Lu, Hua-Lei Yin, Yuan-Mei Xie +2 more

Quantum conference key agreement (QCKA) enables secure communication among multiple parties by leveraging multipartite entanglement, which is expected to play a crucial role in future quantum networks. However, its practical implementation has been severely limited by the experimental complexity and low efficiency associated with the requirement for synchronous detection of multipartite entangled states. In this work, we propose a measurement-device-independent QCKA protocol that employs asynchronous Greenberger-Horne-Zeilinger state measurement. Our protocol enables a linear scaling of the conference key rate among multiple parties, demonstrating performance comparable to that of the single-repeater scheme in quantum networks. Additionally, we achieve intercity transmission distances with composable security under finite-key conditions. By adopting the generalized asynchronous pairing strategy, our approach eliminates the need for complex global phase locking techniques. Furthermore, by integrating asynchronous pairing with ring-interference network structure, our method provides insights for various quantum tasks beyond quantum communication, including multiparty computing and quantum repeaters.

arXiv:2406.15853•Reports on Progress in Physics•May 30, 2025•31 citations

Experimental Efficient Source-Independent Quantum Conference Key Agreement

Wen-Ji Hua, Yi-Ran Xiao, Yu Bao +2 more

Multipartite entanglement enables secure group key distribution among multiple users while providing immunity against hacking attacks targeting source devices, thereby realizing source-independent quantum conference key agreement (SI-QCKA). However, previous experimental demonstrations of SI-QCKA have encountered substantial technical challenges, primarily due to the low efficiency and scalability limitations inherent in the generation and distribution of multipartite entanglement. Here, we experimentally demonstrate a scalable and efficient SI-QCKA protocol using polarization-entangled photon pairs in a three-user star network, where Greenberger-Horne-Zeilinger correlations are realized via a post-matching method. We achieve a secure group key rate of $2.11 \times 10^{4}$ bits/s under the single-user channel transmission of 1.64 $\times$ $10^{-1}$ in a symmetric channel loss network. Additionally, we conduct six sets of experiments to investigate the impact of varying channel transmission and random basis selection probabilities on secure key rates. Our work establishes an efficient pathway for SI-QCKA and demonstrates potential scalability for future large-scale multi-user quantum networks.

quant-pharXiv:2512.20038•Research•Dec 24, 2025•4 citations

Satellite-based tripartite measurement-device-independent quantum conference key agreement

Guoqi Huang, Lu Wang, Wei Cui +2 more

Abstract Measurement-device-independent Quantum conference key agreement (MDI-QCKA) shares secure keys among multiple users by distributing postselected Greenberger-Horne-Zeilinger (GHZ) entanglement, improving practicality and security. Currently, the proposed QCKA protocols can achieve a communication distance of hundreds of kilometers over fiber link. However, such performance is only applicable to quantum communication within an inter-city range. To enable multi-user communication to cover a broader area, quantum satellites offer a solution. Here, one of the communication parties of MDI-QCKA is set as a satellite, and its performance is analyzed in combination with the characteristics of satellite-based link. Simulation results demonstrate the impact of the asymmetry of satellite-based and fiber link on system performance. In addition, considering the fluctuation of satellite-based link, the limitations on system performance caused by atmospheric turbulence, scattering particles, and pointing error are also simulated. These results provide a detailed analysis of the performance of satellite-based MDI-QCKA from the perspectives of satellite operation and the atmospheric environment, contributing to the expansion of MDI-QCKA to future global quantum communication networks.

Physica Scripta•Jun 9, 2025•0 citations

Asymmetric Source-Independent Quantum Conference Key Agreement

H. Wang, Kaiyi Shi, Yujia Zhang +5 more

Abstract Multi-party quantum key sharing is the foundation for constructing quantum communication networks. The source-independent quantum conference key agreement (QCKA) distributes multiple Bell state pairs, which are post-processed to construct equivalent Greenberger-Horne-Zeilinger (GHZ) states and achieve multi-party key sharing. This helps maintain key rates at reasonable levels as the number of users increases, improving practicality and scalability. However, in the original source-independent QCKA protocol, the users receiving Bell states are assumed to be symmetrically distributed, which actually contradicts the distinct functional roles of the protocol participants (Alice and Bobs), and also limits the conference key rate of the protocol. To address this, we propose a source-independent QCKA protocol under an asymmetric architecture and perform simulations using parameters from existing commercial products, increasing the conference key rate and reducing deployment costs in practical applications.

Chinese Physics B•Jun 30, 2026•0 citations

Performance Analysis of Multiparty GHZ-State Quantum Conference Key Agreement over Optical Fiber Channel

Dipanjan Bera, Ramniwas Meena, Neel Kanth Kundu

Quantum conference key agreement (QCKA) enables multiple spatially separated users to establish a common key with composable information-theoretic security by exploiting multipartite quantum correlations. Greenberger--Horne--Zeilinger (GHZ) states are a natural resource for this task, but their distribution over optical fiber is degraded by transmission loss, polarization decoherence, and detector imperfections. We investigate the finite-key performance of an $N$-party GHZ-based QCKA system using the $N$-BB84 protocol, where each optical link is modeled by extending the bipartite erasure--Pauli channel to incorporate detector dark counts. We characterize the impact of this quantum channel on the shared GHZ state and derive closed-form expressions for the error rates. The analytical results reveal that the local bit-error rate depends only on transmissivity and dark counts, while the global phase-error rate compounds over all $N-1$ links and therefore degrades faster with both distance and the number of parties. These error rates are integrated into a finite-key secret-key-rate (SKR) framework, in which we optimize the parameter-estimation probability via Brent's derivative-free method. Numerical results show that increasing fiber distance and network size reduce the achievable SKR. Furthermore, the optimized parameter-estimation probability consistently increases the SKR and extends the maximum secure distance relative to a fixed-allocation baseline, with comparison to the asymptotic limit quantifying the residual finite-key penalty.

quant-pharXiv:2610.05448•Oct 6, 2026•0 citations

Experimental Measurement-Device-Independent Quantum Cryptographic Conferencing

Yifeng Du, Yufeng Liu, Chengdong Yang +3 more

Quantum cryptographic conferencing (QCC) allows sharing secret keys among multiple distant users and plays a crucial role in quantum networks. Because of the fragility and low generation rate of genuine multipartite entangled states required in QCC, realizing and extending QCC with the entanglement-based protocol is challenging. Measurement-device-independent (MDI) QCC, which removes all detector side channels, is a feasible long-distance quantum communication scheme to practically generate multipartite correlation with multiphoton projection measurement. Here we experimentally realize the three-user MDI QCC protocol with four-intensity decoy-state method, in which we employ the polarization encoding and the Greenberger-Horne-Zeilinger state projection measurement. Our work demonstrates the experimental feasibility of the MDI QCC, which lays the foundation for the future realization of quantum networks with multipartite communication tasks.

arXiv:2411.14890•Physical Review Letters•Jan 31, 2025•13 citations
Quantum networks aim to enable quantum information tasks among multiple parties. Quantum conference key agreement (QCKA) is a typical task in quantum networks, which distributes information-theoretically secure keys among multiple users. However, QCKA relying on directly distributing Greenberger-Horne-Zeilinger (GHZ) states over long distances faces significant challenges due to the fragility of these states. Measurement-device-independent QCKA (MDI-QCKA) based on distributing the postselected GHZ entanglement can address this issue and eliminate all loopholes in detection side channels. Here, by developing three-photon GHZ interference technology with high visibility among three independent coherent sources, we realized the first MDI-QCKA experiment over a 60 km fiber link, achieving a secret key rate of 45.5 bits/s. Our result represents a significant step towards practical long-distance QCKA using realistic devices. Moreover, the technology we developed opens the way to future multiparty quantum communications in quantum networks.
Quantum conference key agreement (QCKA) enables secure communication among multiple parties by leveraging multipartite entanglement, which is expected to play a crucial role in future quantum networks. However, its practical implementation has been severely limited by the experimental complexity and low efficiency associated with the requirement for synchronous detection of multipartite entangled states. In this work, we propose a measurement-device-independent QCKA protocol that employs asynchronous Greenberger-Horne-Zeilinger state measurement. Our protocol enables a linear scaling of the conference key rate among multiple parties, demonstrating performance comparable to that of the single-repeater scheme in quantum networks. Additionally, we achieve intercity transmission distances with composable security under finite-key conditions. By adopting the generalized asynchronous pairing strategy, our approach eliminates the need for complex global phase locking techniques. Furthermore, by integrating asynchronous pairing with ring-interference network structure, our method provides insights for various quantum tasks beyond quantum communication, including multiparty computing and quantum repeaters.
Multipartite entanglement enables secure group key distribution among multiple users while providing immunity against hacking attacks targeting source devices, thereby realizing source-independent quantum conference key agreement (SI-QCKA). However, previous experimental demonstrations of SI-QCKA have encountered substantial technical challenges, primarily due to the low efficiency and scalability limitations inherent in the generation and distribution of multipartite entanglement. Here, we experimentally demonstrate a scalable and efficient SI-QCKA protocol using polarization-entangled photon pairs in a three-user star network, where Greenberger-Horne-Zeilinger correlations are realized via a post-matching method. We achieve a secure group key rate of 2.11×1042.11 \times 10^{4}2.11×104 bits/s under the single-user channel transmission of 1.64 ×\times× 10−110^{-1}10−1 in a symmetric channel loss network. Additionally, we conduct six sets of experiments to investigate the impact of varying channel transmission and random basis selection probabilities on secure key rates. Our work establishes an efficient pathway for SI-QCKA and demonstrates potential scalability for future large-scale multi-user quantum networks.
Abstract Measurement-device-independent Quantum conference key agreement (MDI-QCKA) shares secure keys among multiple users by distributing postselected Greenberger-Horne-Zeilinger (GHZ) entanglement, improving practicality and security. Currently, the proposed QCKA protocols can achieve a communication distance of hundreds of kilometers over fiber link. However, such performance is only applicable to quantum communication within an inter-city range. To enable multi-user communication to cover a broader area, quantum satellites offer a solution. Here, one of the communication parties of MDI-QCKA is set as a satellite, and its performance is analyzed in combination with the characteristics of satellite-based link. Simulation results demonstrate the impact of the asymmetry of satellite-based and fiber link on system performance. In addition, considering the fluctuation of satellite-based link, the limitations on system performance caused by atmospheric turbulence, scattering particles, and pointing error are also simulated. These results provide a detailed analysis of the performance of satellite-based MDI-QCKA from the perspectives of satellite operation and the atmospheric environment, contributing to the expansion of MDI-QCKA to future global quantum communication networks.
Abstract Multi-party quantum key sharing is the foundation for constructing quantum communication networks. The source-independent quantum conference key agreement (QCKA) distributes multiple Bell state pairs, which are post-processed to construct equivalent Greenberger-Horne-Zeilinger (GHZ) states and achieve multi-party key sharing. This helps maintain key rates at reasonable levels as the number of users increases, improving practicality and scalability. However, in the original source-independent QCKA protocol, the users receiving Bell states are assumed to be symmetrically distributed, which actually contradicts the distinct functional roles of the protocol participants (Alice and Bobs), and also limits the conference key rate of the protocol. To address this, we propose a source-independent QCKA protocol under an asymmetric architecture and perform simulations using parameters from existing commercial products, increasing the conference key rate and reducing deployment costs in practical applications.
Quantum conference key agreement (QCKA) enables multiple spatially separated users to establish a common key with composable information-theoretic security by exploiting multipartite quantum correlations. Greenberger--Horne--Zeilinger (GHZ) states are a natural resource for this task, but their distribution over optical fiber is degraded by transmission loss, polarization decoherence, and detector imperfections. We investigate the finite-key performance of an NNN-party GHZ-based QCKA system using the NNN-BB84 protocol, where each optical link is modeled by extending the bipartite erasure--Pauli channel to incorporate detector dark counts. We characterize the impact of this quantum channel on the shared GHZ state and derive closed-form expressions for the error rates. The analytical results reveal that the local bit-error rate depends only on transmissivity and dark counts, while the global phase-error rate compounds over all N−1N-1N−1 links and therefore degrades faster with both distance and the number of parties. These error rates are integrated into a finite-key secret-key-rate (SKR) framework, in which we optimize the parameter-estimation probability via Brent's derivative-free method. Numerical results show that increasing fiber distance and network size reduce the achievable SKR. Furthermore, the optimized parameter-estimation probability consistently increases the SKR and extends the maximum secure distance relative to a fixed-allocation baseline, with comparison to the asymptotic limit quantifying the residual finite-key penalty.
Quantum cryptographic conferencing (QCC) allows sharing secret keys among multiple distant users and plays a crucial role in quantum networks. Because of the fragility and low generation rate of genuine multipartite entangled states required in QCC, realizing and extending QCC with the entanglement-based protocol is challenging. Measurement-device-independent (MDI) QCC, which removes all detector side channels, is a feasible long-distance quantum communication scheme to practically generate multipartite correlation with multiphoton projection measurement. Here we experimentally realize the three-user MDI QCC protocol with four-intensity decoy-state method, in which we employ the polarization encoding and the Greenberger-Horne-Zeilinger state projection measurement. Our work demonstrates the experimental feasibility of the MDI QCC, which lays the foundation for the future realization of quantum networks with multipartite communication tasks.