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Chinese Physics B

Improved model on asynchronous measurement-device-independent quantum key distribution with realistic devices

Ming-Shuo Sun, Chunhui Zhang, Rui Zhang, Xingyu Zhou, Jian Li, Qin Wang

Published Aug 30, 2024• 2 citations
Publisher

Abstract

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.

DOI
10.1088/1674-1056/ad757a

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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.
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.
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 1010%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.
The linear constraint of secret key rate capacity is overcome by the twin-field quantum key distribution (QKD). However, the complex phase-locking and phase-tracking technique requirements throttle the real-life applications of the twin-field protocol. The asynchronous measurement-device-independent (AMDI) QKD, also called the mode-pairing QKD, protocol can relax the technical requirements and keep the similar performance of the twin-field protocol. Here, we propose an AMDI-QKD protocol with a nonclassical light source by changing the phase-randomized weak coherent state to a phase-randomized coherent-state superposition in the signal state time window. Simulation results show that our proposed hybrid source protocol significantly enhances the key rate of the AMDI-QKD protocol, while exhibiting robustness to imperfect modulation of nonclassical light sources.
In the realm of long-distance quantum communication, asynchronous measurement-device-independent quantum key distribution (AMDI-QKD) stands out for its experimental simplicity and high key rate generation. Despite these advantages, there exists a challenge in finding a balance between simplifying the laser system further and achieving high key rates. To address this challenge, we have devised a postmeasurement compensation scheme to accurately estimate the mutual frequency offset between two compact lasers using just the announced quantum-signal detection results, thereby obviating the need for optical reference light. As a result, we demonstrate an AMDI-QKD system operating at 2.5 GHz and achieving secure key rates (SKRs) of 537 and 101 kbit / s at distances of 100 and 201 km, respectively, showcasing a significant key rate improvement compared to similar setups. By leveraging ultrastable lasers, we achieve the highest SKRs with measurement-device-independent security within the 100–400-km range. Over 100 km, we reach a remarkable key rate of 1.03 Mbit / s , which could enable real-time one-time-pad video encryption. These findings render AMDI-QKD as a promising contender for the establishment of high performance and cost-effective large-scale intercity quantum networks.
Abstract Asynchronous quantum key distribution protocol (AMDI‐QKD) is a high performance quantum key distribution protocol while it can outperform the Pirandola–Laurenza–Ottaviani–Banchi (PLOB) bound without the need of phase‐locking and phase‐tracking techniques. However, the protocol applies the relative phase information of the communicating parties for encoding, and the drift of the reference frame inevitably affects the performance of the QKD system, whereas reference frame independent quantum key distribution (RFI‐QKD) has the advantage of tolerating the slow change of the reference frame. In this study, a reference frame‐independent asynchronous quantum key distribution (RFI‐AMDI‐QKD) scheme is proposed, which does not require phase alignment between the interferometers of both parties, and it is shown that the protocol can transmit over long distances and is robust to the drift of the reference frame.
In theory, quantum key distribution (QKD) promises unconditional secure generation of the key between two remote participants, based on the laws of quantum physics. However, because of the imperfections in the real-life implementation of QKD, this promise fails. To fill the gap between the theory and implementation of QKD, different protocols have been proposed. One of them is measurement device independent (MDI) QKD, which can be implemented using present-day technology and generates a reasonable key rate. The protocol works perfectly fine for intracity communication. However, the transmission distance is not enough, so that it can replace intercity communication. For that, adaptive measurement device-independent (AMDI) QKD has been proposed. So, the present-day classical communication network such as the internet can be replaced with its quantum version. Till the date, AMDI-QKD has been implemented with threshold detectors. In this paper, we replaced threshold detectors with photon-number resolving detectors, thus making the protocol more realistic. We calculated the secret key rate for the case and discussed its dependence on transmission distance. We also discussed the dependence of the sifted key rate and quantum bit error rate (QBER) on the transmission distance.