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Chinese Physics Letters

Practical 15 Mb/s Quantum Key Distribution Using Compact Single-Photon Detectors

Tingting 婷婷 Shi 施, Zhengyu Yan, Yuanbin Fan, Lai Zhou, Yuanfei Gao, Davide G. Marangon, Zhiliang L. Yuan

Published Nov 1, 2025• 1 citation
Publisher

Abstract

Abstract Quantum key distribution (QKD) is recognized as an unconditionally secure method of communication encryption, relying solely on the principles of quantum mechanics. A key performance metric for QKD systems is secure key rate (SKR), which is a critical factor for real-world applications. Herein, we report a practical QKD system, equipped with compact gated InGaAs/InP single-photon detectors (SPDs), that can generate a high SKR of 15.2 Mb/s with a channel loss of 2 dB. This exceptional performance stems from the ultra-low afterpulsing probability of the SPDs, which significantly reduces the bit error rate in the QKD system. The typical quantum bit error rate is 1.3%. The results validate the feasibility of an integrated, practical QKD system and offer a reliable solution for the future development of real-world QKD networks.

DOI
10.1088/0256-307x/42/12/120602

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Abstract Quantum key distribution (QKD) is recognized as an unconditionally secure method of communication encryption, relying solely on the principles of quantum mechanics. A key performance metric for QKD systems is secure key rate (SKR), which is a critical factor for real-world applications. Herein, we report a practical QKD system, equipped with compact gated InGaAs/InP single-photon detectors (SPDs), that can generate a high SKR of 15.2 Mb/s with a channel loss of 2 dB. This exceptional performance stems from the ultra-low afterpulsing probability of the SPDs, which significantly reduces the bit error rate in the QKD system. The typical quantum bit error rate is 1.3%. The results validate the feasibility of an integrated, practical QKD system and offer a reliable solution for the future development of real-world QKD networks.
Integrated photonics has the advantages of miniaturization, low cost, and CMOS compatibility, and it provides a stable, highly integrated, and practical platform for quantum key distribution (QKD). While photonic integration of optical components has greatly reduced the overall cost of QKD systems, single-photon detectors (SPDs) have become the most expensive part of a practical QKD system. In order to circumvent this obstacle and make full use of SPDs, we have designed and fabricated a QKD receiver chip for multiple users. Our chip is based on a time-division multiplexing technique and makes use of a single set of SPDs to support up to four users' QKD. Our proof-of-principle chip-based QKD system is capable of producing an average secret key rate of 13.68 kbps for four users with a quantum bit error rate (QBER) as low as 0.51% over a simulated distance of 20 km in fiber. Our result clearly demonstrates the feasibility of multiplexing SPDs for setting QKD channels with different users using photonic integrated chip and may find applications in the commercialization of quantum communication technology.
Quantum key distribution (QKD) enables secure communication by harnessing the fundamental principles of quantum physics, which inherently guarantee information-theoretic security and intrinsic resistance to quantum computing attacks. However, the secure key rate of QKD typically decreases exponentially with increasing channel distance. In this work, by developing a novel polarization-state preparation method, an ultra-low time-jitter laser source and superconducting nanowire single-photon detectors, we demonstrate a 5-GHz integrated QKD system featuring ultra-low quantum bit error rates (QBERs). The system achieves secure key rates of 1.076 Mbps at 150 km and 105 kbps at 200 km over standard single-mode fiber channels, respectively. Our system substantially enhances the secure key rate, enabling high-resolution video calls with one-time-pad encryption over intercity backbone QKD links. This work represents a significant step forward in the development of high-performance practical QKD systems.
Quantum communication, in particular, quantum key distribution (QKD) is moving ever closer to real world implementation. However, for successful QKD system deployment, the QKD system components must be robustly designed and feature highly reliable operation. In this paper we focus on one important aspect of any quantum communication system: the single photon detector. In particular our interest is centered upon the InGaAs avalanche photodiode (APD) single photon detector operating in a self-differencing (SD) mode. Such a detector features high clock frequencies of up to 3GHz, high photon count rates as well as detection efficiencies approaching 20% with low afterpulsing. We show successful operation of a high bit rate QKD system using this SD-APD technology in a real world fiber network.
Quantum key distribution (QKD) is a promising technology for information-theoretic secure communications. The practicality of QKD systems is critical for large-scale network deployment, requiring both high key generation rate and miniaturized modules for quantum-state preparation and detection. Here, we report a deployable QKD system that achieves secure key rates of 60.33 ± 0.03 Mbps at 10 km and 3.08 ± 0.20 Mbps at 100 km. The system integrates a dual-parallel Mach-Zehnder encoder to achieve high-fidelity, unified preparation of polarization and decoy states via single-step modulation in a compact design. Meanwhile, we developed miniaturized single-photon avalanche detectors operating at 2.5 GHz, achieving high count rates while maintaining low noise. This high-performance and compact solution establishes a feasible roadmap for urban secure communication networks that require high capacity and bandwidth.
Quantum key distribution (QKD) enables information-theoretically secure key establishment, yet its practical performance strongly depends on the behavior of singlephoton detectors. In high-speed systems, afterpulsing effect and dead time can distort detection statistics and cause substantial overestimation of the secure key rate if not properly modeled. To address this issue, we construct a625−MHz625-\text{MHz}625−MHzBB84-QKD system based on a silica planar-lightwave-circuit asymmetric MachZehnder interferometer chips, incorporate a dependency-modelbased description of detector afterpulse and dead time into the theoretical analysis. This model provides corrected estimations of gain and error rates that more accurately reflect the real detection process. Experimental results show that the system achieves secure key rate of 30.47 kbps at 18 dB channel loss. The strong agreement between the corrected model and measured data confirms that it effectively avoids key-rate overestimation and reliably predicts system performance under practical conditions. The demonstrated on-chip encoding-decoding architecture and refined detector modeling together highlight a promising route toward compact, stable, and high-speed QKD systems, offering valuable guidance for future metropolitan and large-scale quantum communication networks.
Quantum Key Distribution (QKD) systems based on single photon transmission can generate unconditionally secure common key between remote users. Improvement of QKD performance, particularly on key generation rate, has been required to meet current network traffic. High key generation rate is realized by increasing photon detection rate and by reducing error rate. Therefore, a high-speed QKD system should be equipped with low loss receivers with high visibility, highly efficient photon detectors with small dark count probability, and a stable clock synchronization system with low stray light to the quantum signals. A solution for these issues are given by employing planar lightwave circuit interferometers, single photon detection circuits and modules, and clock synchronization based on Wavelength Division Multiplexing (WDM) technique.