Abstract Measurement-device-independent quantum key distribution (MDI-QKD), a key protocol in quantum communication, can eliminates measurement-device vulnerabilities. In practical implementations, however, imperfect encoding modulation may introduce side-channel information leakage, while channel loss significantly reduces the coincidence count rate in Bell-state measurements, thereby limiting both the achievable secret key rate and transmission distance. To address these issues, we propose a memory-assisted MDI-QKD scheme with Hong-Ou-Mandel (HOM)-based source monitoring. The HOM-based monitoring mechanism enables source-side characterization of state-preparation imperfections and provides rigorous security constraints for secret key rate estimation, while the quantum memory enhances the effective two-photon interference probability and improves the success rate of Bell-state measurements. Numerical simulations show that the proposed scheme outperforms conventional source-monitoring-assisted MDI-QKD schemes without quantum memories in both secret key rate and transmission distance, highlighting its potential for practical long-distance quantum communication.
Abstract Measurement-device-independent quantum key distribution (MDI-QKD), a key protocol in quantum communication, can eliminates measurement-device vulnerabilities. In practical implementations, however, imperfect encoding modulation may introduce side-channel information leakage, while channel loss significantly reduces the coincidence count rate in Bell-state measurements, thereby limiting both the achievable secret key rate and transmission distance. To address these issues, we propose a memory-assisted MDI-QKD scheme with Hong-Ou-Mandel (HOM)-based source monitoring. The HOM-based monitoring mechanism enables source-side characterization of state-preparation imperfections and provides rigorous security constraints for secret key rate estimation, while the quantum memory enhances the effective two-photon interference probability and improves the success rate of Bell-state measurements. Numerical simulations show that the proposed scheme outperforms conventional source-monitoring-assisted MDI-QKD schemes without quantum memories in both secret key rate and transmission distance, highlighting its potential for practical long-distance quantum communication.
The measurement-device-independent quantum key distribution (MDI QKD) can resist all attacks against measurement devices. However, its practical performance is still limited due to very low coincidence counting rates in Bell-state measurements. In this paper, we propose a practical memory-assisted MDI QKD protocol by cooperating the heralded single-photon sources and an all-optical quantum memory. By making use of the heralding characteristic of heralded single-photon sources, the earlier photon will be stored in the Sagnac optical quantum memory, and then released till another photon's arrival. Moreover, by combining with the decoy-state method, the present work exhibits significantly improved key rates and transmission distances compared with all existing MDI QKD protocols without using quantum memories. Therefore, this work can provide valuable references for practical implementation of long-distance quantum communications.
Measurement-device-independent quantum key distribution (MDI-QKD) protocol can effectively resist all possible attacks targeting the measurement devices in a quantum key distribution (QKD) system, thus exhibiting high security. However, due to the protocol’s high sensitivity to channel attenuation, its key generation rate and transmission distance are significantly limited in practical applications. To improve the performance of MDI-QKD, researchers have proposed quantum-memory (QM)-assisted MDI-QKD protocol, which has enhanced the protocol's performance to a certain extent. Nevertheless, under finite-size conditions where the total number of transmitted pulses is limited, accurately estimating the relevant statistical parameters is still a challenge. As a result, existing QM-assisted MDI-QKD schemes still encounters issues such as low key rates and limited secure transmission distances. To solve these problems, this work proposes a novel improved finite-size QM-assisted MDI-QKD protocol. By utilizing quantum memories to temporarily store early-arriving pulses and release them synchronously, the protocol effectively reduces the influence caused by channel asymmetry. Additionally, the protocol introduces a four-intensity decoy-state method to improve the estimation accuracy of single-photon components. Meanwhile, to mitigate the influence of finite-length effects on QM schemes, the proposed protocol combines a collective constraint model and a double-scanning algorithm to jointly estimate scanning error counts and vacuum-related counts. This approach enhances the estimation accuracy of the single-photon detection rate and phase error rate under finite-size conditions, thereby significantly improving the secure key rate of the MDI-QKD system. Simulation results show that under the same experimental conditions, compared with the existing QM-assisted three-intensity decoy-state MDI-QKD protocol and the four-intensity decoy-state MDI-QKD protocol based on Heralded Single-photon Source (HSPS), the proposed protocol extends the secure transmission distance by more than 30 km and 100 km, respectively. This proves that under the same parameter settings, the proposed scheme exhibits significant advantages in both key rate and secure transmission distance. Therefore, this research provides important theoretical references and valuable benchmarks for developing long-distance, high-security quantum communication networks.
Measurement-device-independent quantum key dis-tribution (MDI-QKD) can remove all detector side-channel attacks. However, there are still some assumptions on source preparations in MDI-QKD protocols, which are too strict to achieve in real-life implementations. To remove those assump-tions, here we construct a scheme on characterizing the source modulation errors with Hong-Ou-Mandel (HOM) interferences. Furthermore, we combine it with the decoy-state method and present the security analysis. Besides, finite data-size effects are taken into account as well. Simulation results verify the feasibility and practicability of this scheme. It thus seems a very promising candidate for constructing high-security network in the near future.
Measurement-device-independent quantum key distribution (MDI-QKD) is proposed to close the loopholes of the detection part in QKD systems, while it still requires the light source to be trusted. This assumption is not guaranteed in practice, leading to practical secure issues. In this paper, we propose a light source monitoring scheme with single-photon detectors for MDI-QKD, which can guarantee the security of the system under the untrusted source condition with both common decoy state method and the newly proposed five-intensity decoy state method. Moreover, our monitoring scheme performs almost the same as the ideal MDI protocol even considering the imperfect factors in practical systems. Compared to the previous scheme, our work improves the secure key rate and the transmission distance of practical MDI-QKD systems significantly.
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.
Measurement-device-independent quantum secret sharing (MDI-QSS) can resist all attacks on imperfect measuring devices. However, limited by the exponential increase in fiber loss, MDI-QSS has a low key rate and short communication distance. In this paper, we introduce quantum memory (QM) in MDI-QSS to increase the success probability of the three-photon synchronous projection measurement and propose a memory-assisted (MA) MDI-QSS protocol. In this protocol, the heralded single-photon source and the decoy-state method are also explored. This MA-MDI-QSS protocol has three advantages. First, the QM used here is all optical, and this protocol is feasible under current experimental conditions. Second, combined with the decoy-state method, our protocol can guarantee the security of the transmitted keys under practical experimental conditions. Third, numerical simulation results show that our protocol has a higher secure key rate and longer photon transmission distance than existing MDI-QSS protocols without QM. Our protocol provides a promising way for implementing the long-distance MDI-QSS in the near future.