A high-rate continuous-variable quantum key distribution (CV-QKD) system based on high-order discrete modulation is experimentally investigated. With the help of the novel system scheme, effective digital signal processing (DSP) algorithms and advanced analytical security proof methods, the transmission results of 5.059 km, 10.314 km, 24.490 km, and 50.592 km are achieved for 1 GBaud optimized quantum signals. Correspondingly, the asymptotic secret key rates (SKRs) are 292.185 Mbps, 156.246 Mbps, 50.491 Mbps, and 7.495 Mbps for discrete Gaussian (DG) 64QAM, and 328.297 Mbps, 176.089 Mbps, 51.304 Mbps, and 9.193 Mbps for DG 256QAM, respectively. Under the same parameters, the achieved SKRs of DG 256QAM is almost same as ideal Gaussian modulation. In this case, the demonstrated high-rate discrete-modulated CV-QKD system has the application potential for high-speed security communication under tens of kilometers.

We experimentally demonstrated a sub-Mbps key rate Gaussian-modulated coherent-state (GMCS) continuous-variable quantum key distribution (CV-QKD) over a 100-km transmission distance. To efficiently control the excess noise, the quantum signal and the pilot tone are co-transmitted in the fiber channel based on wideband frequency and polarization multiplexing methods. Furthermore, a high-accuracy data-assisted time domain equalization algorithm is carefully designed to compensate the phase noise and polarization variation in low signal-to-noise ratio. The asymptotic secure key rate (SKR) of the demonstrated CV-QKD is experimentally calculated to be 7.55 Mbps, 1.87 Mbps, and 0.51 Mbps over a transmission distance of 50 km, 75 km, and 100 km, respectively. The experimentally demonstrated that the CV-QKD system significantly improves the transmission distance and SKR compared to the state-of-art GMCS CV-QKD experimental results, and shows the potential for long-distance and high-speed secure quantum key distribution.

Quantum key distribution, which ensures information-theoretically secret key generation, is currently advancing through photonic integration to achieve high performance, cost reduction, and compact size, thereby facilitating the large-scale deployment. Continuous-variable quantum key distribution is an attractive approach for photonic integrations due to its compatibility with off-the-shelf optical communication devices. However, its chip-based systems have encountered significant limitations primarily related to the shot-noise-limited receiver design, which demands low noise, wide bandwidth, high clearance, and well stability. Here, we report the implementation of a real local oscillator continuous-variable quantum key distribution system with an integrated silicon photonic receiver chip. Thanks to the well-designed chip-based homodyne detectors with a bandwidth up to 1.5 GHz and a clearance up to 7.42 dB, the transmission distance of the system has been extended to 28.6 km, achieving a secret key generation rate of Mbps level. This technological advancement enables the quantum key distribution systems with photonic integrated receivers to achieve the coverage in both access network scenarios and short-distance metropolitan interconnections, paving the way for the development of the next-generation quantum key distribution networks on a large scale.

With the development of big data and blockchain, an increasing number of scholars have begun to study blockchain for data sharing. By studying data sharing models that are based on blockchain, we find that almost all of them have the following problems: 1) it is difficult to protect the privacy and integrity of users’ data, along with users’ data ownership; 2) the storage burden of blockchain is heavy, and blockchain lacks a mechanism for dealing with data with diverse types and inconsistent formats; and 3) the consensus mechanism has low fairness or low efficiency. Therefore, we propose a data-sharing privacy protection model (DS2PM) that is based on blockchain and a federated learning mechanism for solving these problems. The safety analysis and experimental results show that the DS2PM outperforms the previously established schemes.

Quantum key distribution offers information-theoretic security and is advancing toward real-world quantum secure networks. To meet the growing demand for scalable solutions, we present a high-rate quantum access network (QAN) with 16 user nodes based on a passive optical network, where a highly efficient coherent-state point-to-multipoint (PTMP) protocol is designed for concurrent independent secret key generation between one transmitter and multiple receivers. Such accomplishment is attributed to a subtle shot-noise calibration method, advanced digital signal processing algorithms, and a flexible post-processing strategy. Finally, the experimentally estimated average secret key rate is approximately 2.086 Mbps between the transmitter and each user, two orders of magnitude higher than previous demonstrations. With low cost, excellent compatibility, and wide bandwidth, our work paves the way for practical PTMP QANs, representing a key step toward scalable quantum secure networks.