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Advanced Quantum Technologies

Measurement‐Device‐Independent Continuous‐Variable Quantum Secret Sharing

Qin Liao, Lei Huang, Zhuoying Fei, Xiquan Fu

Published Feb 6, 2025• 8 citations
Publisher

Abstract

Abstract Although continuous‐variable quantum secret sharing (CVQSS) is theoretically proven to be secure, it may still be subject to various practical attacks due to the imperfections of devices. In this study, measurement‐device‐independent CVQSS (MDI‐CVQSS) is proposed in which measurement is no longer the duty for the dealer but is performed by an untrusted party Charlie, so that all detector side‐channel attacks can be eliminated, greatly enhancing the practical security of CVQSS system. The security bound is derived for the proposed MDI‐CVQSS, and its numerical simulation shows that MDI‐CVQSS outperforms conventional CVQSS in terms of both secret key rate and maximal number of users. It is found that MDI‐CVQSS possesses several unique properties, such as local stability of the secret key rate, low total excess noise and high utilization rate of raw data, which indicate that MDI‐CVQSS has the potential for efficiently building a large‐scale quantum communication network. Moreover, it is also suggested three variations of MDI‐CVQSS to satisfy the requirements of different multi‐point quantum communication scenarios.

DOI
10.1002/qute.202400505

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Abstract Although continuous‐variable quantum secret sharing (CVQSS) is theoretically proven to be secure, it may still be subject to various practical attacks due to the imperfections of devices. In this study, measurement‐device‐independent CVQSS (MDI‐CVQSS) is proposed in which measurement is no longer the duty for the dealer but is performed by an untrusted party Charlie, so that all detector side‐channel attacks can be eliminated, greatly enhancing the practical security of CVQSS system. The security bound is derived for the proposed MDI‐CVQSS, and its numerical simulation shows that MDI‐CVQSS outperforms conventional CVQSS in terms of both secret key rate and maximal number of users. It is found that MDI‐CVQSS possesses several unique properties, such as local stability of the secret key rate, low total excess noise and high utilization rate of raw data, which indicate that MDI‐CVQSS has the potential for efficiently building a large‐scale quantum communication network. Moreover, it is also suggested three variations of MDI‐CVQSS to satisfy the requirements of different multi‐point quantum communication scenarios.
Abstract The developing tendency of continuous-variable (CV) measurement-device-independent (MDI) quantum cryptography is to cope with the practical issue of implementing scalable quantum networks. Up to now, most theoretical and experimental researches on CV-MDI QKD are focused on two-party protocols. However, we suggest a CV-MDI multipartite quantum secret sharing (QSS) protocol use the EPR states coupled with optical amplifiers. More remarkable, QSS is the real application in multipartite CV-MDI QKD, in other words, is the concrete implementation method of multipartite CV-MDI QKD. It can implement a practical quantum network scheme, under which the legal participants create the secret correlations by using EPR states connecting to an untrusted relay via insecure links and applying the multi-entangled Greenberger–Horne–Zeilinger (GHZ) state analysis at relay station. Even if there is a possibility that the relay may be completely tampered, the legal participants are still able to extract a secret key from network communication. The numerical simulation indicates that the quantum network communication can be achieved in an asymmetric scenario, fulfilling the demands of a practical quantum network. Additionally, we illustrate that the use of optical amplifiers can compensate the partial inherent imperfections of detectors and increase the transmission distance of the CV-MDI quantum system .
We propose a novel scheme for measurement-device-independent (MDI) continuous-variable quantum key distribution (CVQKD) by simultaneously conducting classical communication and QKD, which is called “simultaneous MDI-CVQKD” protocol. In such protocol, each sender (Alice, Bob) can superimpose random numbers for QKD on classical information by taking advantage of the same weak coherent pulse and an untrusted third party (Charlie) decodes it by using the same coherent detectors, which could be appealing in practice due to that multiple purposes can be realized by employing only single communication system. What is more, the proposed protocol is MDI, which is immune to all possible side-channel attacks on practical detectors. Security results illustrate that the simultaneous MDI-CVQKD protocol can secure against arbitrary collective attacks. In addition, we employ phase-sensitive optical amplifiers to compensate the imperfection existing in practical detectors. With this technology, even common practical detectors can be used for detection through choosing a suitable optical amplifier gain. Furthermore, we also take the finite-size effect into consideration and show that the whole raw keys can be taken advantage of to generate the final secret key instead of sacrificing part of them for parameter estimation. Therefore, an enhanced performance of the simultaneous MDI-CVQKD protocol can be obtained in finite-size regime.
Abstract Building scalable and secure quantum networks requires advanced quantum key distribution (QKD) protocols that support multi-user connectivity. Continuous-variable (CV) measurement-device-independent (MDI) QKD, which eliminates all detector side-channel attacks, is a promising candidate for creating various quantum network topologies-such as quantum access networks and star-type topologies-using standard technology and providing high secure key rates. However, its security has so far only been experimentally demonstrated in asymptotic regimes with limited secret key rates and complex experimental setups, limiting its practical applications. Here, we report an experimental validation of a CV MDI-QKD system, achieving a secure key rate of 2.6 Mbit s −1 against collective attacks in the finite-size regime over a 10 km fiber link. This is achieved using a new system design, incorporating a locally generated local oscillator, a new relay structure, a real-time phase locking system, and a well-designed digital-signal-processing pipeline for quantum state preparation and CV Bell measurements at a symbol rate of 20 MBaud. Our results set a new benchmark for secure key exchange and open the possibility of establishing high-performance CV MDI-QKD networks, paving the way toward a scalable quantum network.
We propose a continuous-variable measurement-device-independent quantum key distribution (CV-MDI QKD) protocol, in which detection is conducted by an untrusted third party. Our protocol can defend all detector side channels, which seriously threaten the security of a practical CV QKD system. Its security analysis against arbitrary collective attacks is derived based on the fact that the entanglement-based scheme of CV-MDI QKD is equivalent to the conventional CV QKD with coherent states and heterodyne detection. We find that the maximal total transmission distance is achieved by setting the untrusted third party close to one of the legitimate users. Furthermore, an alternate detection scheme, a special application of CV-MDI QKD, is proposed to enhance the security of the standard CV QKD system.
Quantum communications can be conveniently implemented by two participants, but quantum secret key sharing (QSS) through multi-participant communication seems difficult in practice. In this paper, we propose a multi-participant QSS scheme with the local local oscillator (LLO) in continuous variable (CV) quantum communications. It allows an honest participant called a dealer to share a secret key with the others, making it possible to establish a secret key if and only if all participants gather together. The LLO scheme, which eliminates the need for the local oscillator (LO) to be propagated in insecure channels, can be used to avoid the potential LO attack in the traditional CVQSS scheme. Numerical simulation shows that the performance of the LLO-based CVQSS can be improved in terms of the maximal transmission distance even if it is performed with the partially trusted noise.
Abstract Continuous-variable quantum secret sharing (CVQSS) is a promising approach to ensuring multi-party information security. While CVQSS offers practical ease of implementation, its present performance remains limited. In this paper, we propose a novel CVQSS protocol integrated with a state-discrimination detector (SDD), dubbed SDD-CVQSS. In particular, we first develop the detailed procedure of SDD-CVQSS, which replaces the traditional coherent detector with an SDD and eliminates the long-standing necessary step of establishing multiple point-to-point quantum key distribution links between all users and the dealer. We then elaborate on the principle of the specifically designed SDD, which can efficiently discriminate interfered states with a much lower error probability. Finally, we construct a security model for SDD-CVQSS and derive its security bound against both eavesdroppers and dishonest users. Numerical simulations show that SDD-CVQSS outperforms conventional CVQSS in terms of both maximum transmission distance and secret key rate, and its performance is even superior to the PLOB bound. Additionally, we find that the performance degradation of SDD-CVQSS in long-distance transmission scenarios can be effectively compensated for using a post-selection scheme, providing a feasible way to achieve high-performance CVQSS.