[en] Based on the fundamental uncertainty of quantum mechanics, quantum random number generators can generate truly random number which is critically important for many applications, such as information security. However, while the generation rate of offline quantum random number generators could be up to tens of Gbps or more, that of real-time quantum random number generators is only 3.2 Gbps due to the relatively low post-processing speed, and the application of real-time quantum random number generators is limited. We propose an efficient and robust high-speed real-time quantum random number generation scheme based on quantum phase fluctuation of a distributed feedback laser, with improved post-processing techniques. Firstly, the quantum signal-to-noise ratio is increased by analyzing and quantifying quantum noise. Secondly, a time-interleaved analog-to-digital converter scheme is designed to achieve a real-time sampling rate of 8 GSa/s. Finally, the random bits are extracted using the minimum entropy estimation and Toeplitz-hashing randomness extraction. Experimental results show that the proposed scheme could achieves a real-time generation rate up to 8.4 Gbps, with an estimated offline generation rate of 82.32 Gbps.

[en] Semi-quantum key distribution describes a system in which a fully quantum user and classical user perform key distribution. The main advantage of key distribution is its security. Owing to the bottlenecks of existing technology, highly attenuated lasers and threshold detectors are required for semi-quantum key distribution; however, these components make semi-quantum key distribution susceptible to eavesdroppers. Our previous study presented the first semi-quantum key distribution experiment and verified the feasibility of the mirror protocol in 2021. Herein, we first build a semi-quantum key distribution channel model and use Gottesman-Lo-Lütkenhaus-Preskill theory to evaluate its safety performance in the case of a quasi-single photon source. Moreover, we determine that an eavesdropper can steal all information through the photon-number-splitting attack without being detected. Therefore, we add decoy states to the semi-quantum key distribution to estimate the furthest transmission distance and secure bit rate under asymptotic conditions. Semi-quantum key distribution can still be achieved safely with highly attenuated lasers and threshold detectors in 150 km.

[en] To improve the efficiency of QKD systems, a new QKD protocol based on classical–quantum polarized channels is proposed in this article. By precoding the raw key with polar codes before communication, this protocol has higher code rate and lower time cost compared with the traditional ones. According to the attack strategies that eavesdroppers might employ, we have analyzed the protocol’s security under ideal and practical channel models. We prove that under proper channel parameter setting, the security of this protocol is not lower than BB84 under intercept strategy.

[en] Highlights: • Using assembly and in-situ reduction strategy, a SERS substrate were synthesized. • The composites show high adsorption for both hydrophobic and hydrophilic molecules. • The composites exhibit remarkable SERS detection and reproducibility for thiram and methylene blue with the limitation of 10⁻⁹ M and 10⁻¹⁵ M, respectively. Surface-enhanced Raman scattering (SERS) spectroscopy is a highly sensitive and nondestructive method to detect a wide range of probe molecules in the field of agriculture and industry. However, to prepare a homogeneous and reproducible SERS substrate is still a great challenge. Herein, we propose a facile strategy to prepare a homogeneous SERS substrate that presents remarkable adsorption and reproducibility by using electrostatic assembly and in-situ reduction technology. The reduced graphene oxide assembled films modified with polyelectrolytes and heptakis (6-deoxy-6-amino)-β-cyclodextrin are used as the template and reducing agent in the preparation process. By means of simply mixing with AgNO₃ solution, composites containing Ag nanoparticles were obtained. The as-prepared composites present great stability and remarkable adsorption for both hydrophobic and hydrophilic molecules, such as thiram and methylene blue. Combined the functions of reduced graphene, polyelectrolytes and β-cyclodextrin components, the composites exhibit highly sensitive SERS signals with inhibiting the influence of fluorescence. The detection limit of thiram and methylene blue are 10⁻⁹ M and 10⁻¹⁵ M, respectively. Furthermore, the composites serve as a reproducible SERS substrate to overcome randomness of SERS results and improve reproducibility. We expect this study to provide a novel method to fabricate more effective SERS substrates.