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Entropy

Multi-User Measurement-Device-Independent Quantum Key Distribution Based on GHZ Entangled State

Ximing Hua, Min Hu, Banghong Guo

Published Jun 18, 2022• 18 citations
Publisher

Abstract

As a multi-particle entangled state, the Greenberger-Horne-Zeilinger (GHZ) state plays an important role in quantum theory and applications. In this study, we propose a flexible multi-user measurement-device-independent quantum key distribution (MDI-QKD) scheme based on a GHZ entangled state. Our scheme can distribute quantum keys among multiple users while being resistant to detection attacks. Our simulation results show that the secure distance between each user and the measurement device can reach more than 280 km while reducing the complexity of the quantum network. Additionally, we propose a method to expand our scheme to a multi-node with multi-user network, which can further enhance the communication distance between the users at different nodes.

DOI
10.3390/e24060841

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As a multi-particle entangled state, the Greenberger-Horne-Zeilinger (GHZ) state plays an important role in quantum theory and applications. In this study, we propose a flexible multi-user measurement-device-independent quantum key distribution (MDI-QKD) scheme based on a GHZ entangled state. Our scheme can distribute quantum keys among multiple users while being resistant to detection attacks. Our simulation results show that the secure distance between each user and the measurement device can reach more than 280 km while reducing the complexity of the quantum network. Additionally, we propose a method to expand our scheme to a multi-node with multi-user network, which can further enhance the communication distance between the users at different nodes.
Greenberger–Horne–Zeilinger (GHZ) state is an essential resource in quantum processing. We propose multiparty measurement-device-independent quantum key distribution (MDI-QKD) protocol based on a fuzzy GHZ state analyzer, which is composed of linear optical components. Our scheme requires only N detectors and N − 1 polarizing beam splitters to realize an N-party MDI-QKD network. From numerical simulations, the security communication distance is improved to 300 km, and key rate is determined to be higher than 10 − 14. Compared with the previous work, our scheme needs less optical components and detectors, is easier to extend more users, and narrows the gap between theory and practice in multiparty MDI-QKD network.
Quantum key distribution is the core technology of quantum communication. In 2012, the Measurement-Device-independent quantum key distribution protocol proposed by Lo et al., referred to as MDI-QKD protocol, can effectively resist detector attacks from eavesdroppers. However, the traditional MDI-QKD only supports two parties, which can no longer meet the actual needs in the era of rapid development of communication technology. Therefore, multi-party quantum key distribution has become one of the current hot spots. This paper proposes a multi-user measurement device-independent QKD method based on the GHZ entanglement state. The GHZ entanglement source is used as the quantum relay, which solves the multi-party communication and greatly improves the safe communication distance.
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 key distribution (QKD) can serve large numbers of users with unconditional secure communication, in which measurement-device-independent (MDI) QKD protocol can conveniently enhance realistic security by eliminating all detector side channels. In multi-user scenarios, MDI-QKD networks should meet the requirements of reliability and robustness. Around the issues, we complete a series of work on performance improvement, low-cost deployment, and robust networking. First is to answer how to change the trusted node to the untrusted node with low cost, here we propose and demonstrate an MDIQKD which is compatible with phase encoding BB84 networks, allowing for economical deployment of MDI-QKD networks and reconciliation between high key rate and high realistic security in the same network. Then we make the MDI networks more robust. We design an MDI-QKD networking scheme for multi-user access where more than two users can generate keys synchronously regardless of aligning reference frames and compensating channel disturbance on polarization. Third, we find a general method to distil secure keys from quantum discord, which is different to the previous entanglement-based frameworks of MDI-QKD, allowing imperfect preparation and measurement of quantum states. The series of work can help the practical application of MDI-QKD networks, and promote the development of quantum networks.
Abstract Measurement-device-independent quantum key distribution (MDI QKD) provides inherent immunity against attacks targeting practical measurement devices. Existing MDI QKD protocols all rely on Bell-state measurements (BSM) to establish correlations between the users. However, the success probability of linear-optics BSM is limited to 50%, which severely restricts the achievable key rate of MDI QKD. We propose a high-capacity MDI QKD protocol with entanglement-assisted linear-optical BSM. This protocol has three advantages. First, compared with the original MDI QKD, at least a 25% increase in the key rate can be achieved. Second, simulation results show that this protocol can effectively increase the maximum photon transmission distance of MDI QKD from 262 km to 272 km. Third, this protocol is feasible in a fully linear-optical system under current experimental conditions. Our protocol provides a potential approach for improving the performance of future quantum communication networks.
Quantum key distribution (QKD) networks are promising to serve large numbers of users with information-theoretic secure communication. In QKD networks, the detection-safe protocol, termed measurement-device-independent (MDI) QKD, can naturally enhance realistic security by supporting untrusted measurement nodes. However, the environmental disturbances to quantum states degrade the performance of multi-user communication. Here we propose an MDI-QKD networking scheme with robustness against environmental disturbance and adaptability to multi-user access, where more than two users can generate keys simultaneously regardless of aligning reference frames and compensating channel disturbance on polarization. To achieve this, we introduce the reference-frame-independent protocol as well as a polarization-compensation-free method, design a multi-user measurement unit, and combine it with original two-user units. The scheme is experimentally demonstrated for the improvement of network robustness and adaptability in multi-user scenarios, and the time and device costs of disturbance compensation can be saved from O ( N ) to O ( 1 ) for an N-user network.