Abstract Quantum key distribution (QKD) is a theoretically unconditionally secure key distribution method based on quantum mechanical principles. Currently, most QKD protocols encode information in the phase domain, making the phase error rate a crucial physical parameter for evaluating protocol performance. In phase-post-selected QKD protocols, the phase error rate depends on interference measurements within non-zero phase intervals, which introduce inherent errors unrelated to eavesdropping and consequently leads to overestimation of the phase error rate. Precise analysis of phase errors can effectively reduce the protocol’s phase error rate, thereby enhancing its performance. In previous work, phase error analysis methods were primarily applied to QKD protocols under asymptotic conditions. In this study, we extend this precise phase error analysis approach to the finite-key regime of asynchronous measurement-device-independent QKD (AMDI-QKD). The performance of the original and enhanced AMDI-QKD protocols was compared under different pulse intensities through numerical simulation, and the results indicate that, compared to the original AMDI-QKD, the enhanced AMDI-QKD protocol combined with precise error analysis can extend the transmission distance by nearly 20 km and effectively reduce the phase error rate.
Abstract Quantum key distribution (QKD) is a theoretically unconditionally secure key distribution method based on quantum mechanical principles. Currently, most QKD protocols encode information in the phase domain, making the phase error rate a crucial physical parameter for evaluating protocol performance. In phase-post-selected QKD protocols, the phase error rate depends on interference measurements within non-zero phase intervals, which introduce inherent errors unrelated to eavesdropping and consequently leads to overestimation of the phase error rate. Precise analysis of phase errors can effectively reduce the protocol’s phase error rate, thereby enhancing its performance. In previous work, phase error analysis methods were primarily applied to QKD protocols under asymptotic conditions. In this study, we extend this precise phase error analysis approach to the finite-key regime of asynchronous measurement-device-independent QKD (AMDI-QKD). The performance of the original and enhanced AMDI-QKD protocols was compared under different pulse intensities through numerical simulation, and the results indicate that, compared to the original AMDI-QKD, the enhanced AMDI-QKD protocol combined with precise error analysis can extend the transmission distance by nearly 20 km and effectively reduce the phase error rate.
Abstract In principle, the asynchronous measurement-device-independent quantum key distribution (AMDI-QKD) can surpass the key rate capacity without phase tracking and phase locking. However, practical imperfections in sources or detections would dramatically depress its performance. Here, we present an improved model on AMDI-QKD to reduce the influence of these imperfections, including intensity fluctuation, the afterpulse effect, and the dead time of detectors. Furthermore, we carry out corresponding numerical simulations. Simulation results show that, by implementing our present work, it can have more than 100 km longer secure transmission distance and one order of magnitude enhancement in the key generation rate after 320 km compared with the standard method. Moreover, our model can still break the Pirandola–Laurenza–Ottaviani–Banchi (PLOB) bound even under realistic experimental conditions.
The advantage distillation (AD) method has proven effective in improving the performance of quantum key distribution (QKD). In this paper we introduce the AD method into a recently proposed asynchronous measurement-device-independent (AMDI) QKD protocol, taking finite-key effects into account. Simulation results show that the AD method significantly enhances AMDI QKD, e.g., extending the transmission distance by 16 km with a total pulse count of $N=7.24\ifmmode\times\else\texttimes\fi{}{10}^{13}$, and enables AMDI QKD, previously unable to generate keys, to generate keys with a misalignment error rate of 10. As the AD method can be directly integrated into the current system through refined postprocessing, our results facilitate the practical implementation of AMDI QKD in various applications, particularly in scenarios with high channel losses and misalignment errors.
Quantum key distribution (QKD) stands as a pioneering method for establishing information-theoretically secure communication channels by utilizing the principles of quantum mechanics. In the security proof of QKD, the phase error rate serves as a critical indicator of information leakage and directly influences the security of the shared key bits between communicating parties, Alice and Bob. In estimating the upper bound of the phase error rate, phase randomization and subsequent postselection mechanisms serve pivotal roles across numerous QKD protocols. However, the nonzero interval of phase postselection will introduce intrinsic errors, leading to an overestimation of phase error rate. Here we make a precise phase-error-rate analysis for QKD protocols with phase postselection, which eliminates error rate associated with nonzero interval and helps us to accurately bound the amount of information an eavesdropper may obtain. We further apply our analysis in sending-or-not-sending twin-field quantum key distribution (SNS-TFQKD) and mode-pairing quantum key distribution (MP-QKD). The simulation results confirm that our precise phase error analysis can noticeably improve the key rate performance especially over long distances in practice. Note that our method does not require alterations to the existing experimental hardware or protocol steps. It can be readily applied within current SNS-TF-QKD and MP-QKD for higher key rate generation.
Quantum key distribution (QKD) stands as a pioneering method for establishing information-theoretically secure communication channels by utilizing the principles of quantum mechanics. In the security proof of QKD, the phase error rate serves as a critical indicator of information leakage and directly influences the security of the shared key bits between communicating parties, Alice and Bob. In estimating the upper bound of the phase error rate, phase randomization and subsequent postselection mechanisms serve pivotal roles across numerous QKD protocols. Here we make a precise phase error rate analysis for QKD protocols with phase postselection, which helps us to accurately bound the amount of information an eavesdropper may obtain. We further apply our analysis in sending-or-not-sending twin-field quantum key distribution (SNS-TFQKD) and mode-pairing quantum key distribution (MP-QKD). The simulation results confirm that our precise phase error analysis can noticeably improve the key rate performance especially over long distances in practice. Note that our method does not require alterations to the existing experimental hardware or protocol steps. It can be readily applied within current SNS-TF-QKD and MP-QKD for higher key rate generation.
Quantum key distribution (QKD) allows the transmission of keys with unconditional security. Nevertheless, a discrepancy remains between the theoretical framework and the practical implementation, as device imperfections are frequently neglected in most QKD protocols. Some previous works proposed to use Hong-Ou-Mandel interference to quantify information leakage from side-channels. However, the security bound was relatively loose, resulting in poor performance. In this paper, we present an improved method for the security analysis of practical QKD protocols and provide a more precise parameter estimation. Furthermore, we apply it to several important QKD protocols, including BB84, measurement-device-independent, and twin-field, and carry out corresponding numerical simulations. Our work demonstrates significant improvements in both the key rate and the transmission distance compared to previous methods, representing a crucial step towards the practical implementation of QKD.
Quantum key distribution (QKD) enables the establishment of shared keys between two distant users, Alice and Bob, based on the fundamental principles of quantum mechanics, and it has proven to possess information-theoretic security. In most of QKD systems, Alice and Bob require a shared reference frame, and real-time calibration of the reference frame increases system costs and reduces its performance. Fortunately, the reference-frame-independent QKD protocol has been proposed, overcoming reference-frame drift issues and receiving widespread attention. However, in practical QKD systems, the non-ideal characteristics of realistic devices introduce certain inconsistency between the theory and the practice. In real-world quantum key distribution systems, device imperfections can lead to security vulnerabilities, thereby reducing system security. For example, imperfections in the encoding apparatus at the source end may result in errors in the quantum states. The inherent defects in the detection part may cause after-pulse effects and dead-time effects, thus reducing the key rate. Therefore, in this work, we propose a practical state-preparation error tolerant reference-frame-independent quantum key distribution protocol by taking imperfections in both the source and the detectors into account. Moreover, a three-intensity decoy-state scheme for modeling analysis and numerical simulations is employed. In this protocol, we reduce the influence of state-preparation errors on the key rate by utilizing virtual state methods to precisely estimate the phase-error rate. Furthermore, by characterizing the effects of after-pulses and dead-time on the key rate, our protocol exhibits higher robustness and can effectively address issues related to detector imperfections. This approach can also be extended to other quantum key distribution protocols with higher security levels, such as measurement-device-independent quantum key distribution protocol and twin-field quantum key distribution, further mitigating the influence of device imperfections on practical implementation of QKD system. Therefore, our present work provide important reference value for putting the quantum key distributions into practical application.