The quantum network makes use of quantum states to transmit data, which will revolutionize classical communication and allow for some breakthrough applications. Quantum key distribution (QKD) is one prominent application of quantum networks, and can protect data transmission through quantum mechanics. In this work, we propose an expandable and cost-effective quantum access network, in which the round-trip structure makes quantum states travel in a circle to carry information, and the multi-band technique is proposed to support multi-user access. Based on the round-trip multi-band quantum access network, we realize multi-user secure key sharing through the continuous-variable QKD (CV-QKD) protocol. Due to the encoding characteristics of CV-QKD, the quadrature components in different frequency bands can be used to transmit key information for different users. The feasibility of this scheme is confirmed by comprehensive noise analysis, and is verified by a proof-of-principle experiment. The results show that each user can achieve excess noise suppression and 600 bit/s level secure key generation under 30 km standard fiber transmission. Such networks have the ability of multi-user access theoretically and could be expanded by plugging in simple modules. Therefore, it paves the way for near-term large-scale quantum secure networks.

流式细胞显微图像分析法是水体浮游藻类自动鉴别的重要发展方向，快速进样条件下细胞显微图像将产生形变，影响浮游藻类自动鉴别准确率。本文基于搭建的浮游藻类微流控-显微成像实验系统，通过对不同进样流速下藻类细胞显微形变和图像清晰度的分析，研究了流速对显微成像形变的影响规律。分析基于卷帘快门拍摄运动物体产生形变原理，提出了单向偏移像素的图像形变校正方法，并与藻类细胞静态条件下获取的图像进行了对比分析。实验结果表明：静态条件下，湖生卵囊藻细胞的图像长宽比及清晰度均值分别为1.16和116.53；动态进样过程中，随着流速增大细胞图像形变（长宽比）逐渐增大、清晰度降低；95 µL/min进样流速下，校正前后细胞图像长宽比均值分别为1.35和1.26，形变离散程度由校正前的0.33降至0.1，与静态细胞形态接近且校正前后图像清晰度基本不变。本文研究结果为提升水体浮游藻类细胞自动鉴别准确率提供了依据。

借鉴玻璃透镜的研究方法，提出了一种基于统计数据的液体透镜重复变焦精度指标，用于描述其变焦稳定性，并给出了液体透镜设计参数优化及材料优选的实验方法。首先，通过初步实验研究与分析，得到影响液体透镜重复变焦精度的主要影响因素——极性溶液体积、锥度、非极性溶液粘度；其次，以重复变焦精度和变焦范围作为评价指标，发现重复变焦精度与电压的关系不具有单调性，存在先升后降的现象。在此基础上，运用极差分析与综合平衡法，得到各因素的不同影响程度及最优参数组合，采用正交实验法优化设计参数。最后，实验验证了该方法的有效性。实验结果表明，优化后的液体透镜，在150 V电压处，重复变焦精度为0.2 m⁻¹；在0~230 V电压范围内，变焦范围为−15.2~5.85 m⁻¹。结果表明本文所提出的方法基本满足液体透镜变焦稳定可靠、精度高、变焦范围大等要求。

针对目前浮游植物种类鉴别镜检法中存在的相似形态藻细胞难以区分、同粒径杂质干扰大、藻细胞位置难以定位分割等问题，设计了一种浮游植物明场荧光显微同步成像系统。系统使用高分辨显微成像光路结构、透射式与落射式结合的照明方式和以分光光路为核心的明场荧光双光路同步成像方法，获取浮游植物显微图像下的明场形态信息和色素荧光信息。利用该系统对绿藻门、蓝藻门、硅藻门等不同门类藻种进行明场图像与荧光图像同步成像测试，实验结果表明：系统成像分辨率达1.5 μm，成像周期时间为707 ms，系统采集的图片中藻细胞纹理清晰，细胞边缘明显，利用系统中的明场图像并结合荧光图像，可有效定位藻细胞位置，降低样品中杂质对藻种鉴别的影响，丰富浮游植物显微图像信息量，为基于浮游植物显微图像的相关研究提供方法参考。

The finding of the robust ferroelectricity in HfO₂-based thin films is fantastic from the view point of both the fundamentals and the applications. In this review article, the current research status of the future prospects for the ferroelectric HfO₂-based thin films and devices are presented from fundamentals to applications. The related issues are discussed, which include: 1) The ferroelectric characteristics observed in HfO₂-based films and devices associated with the factors of dopant, strain, interface, thickness, defect, fabrication condition, and more; 2) physical understanding on the observed ferroelectric behaviors by the density functional theory (DFT)-based theory calculations; 3) the characterizations of microscopic and macroscopic features by transmission electron microscopes-based and electrical properties-based techniques; 4) modeling and simulations, 5) the performance optimizations, and 6) the applications of some ferroelectric-based devices such as ferroelectric random access memory, ferroelectric-based field effect transistors, and the ferroelectric tunnel junction for the novel information processing systems.

Integrated quantum key distribution (QKD) systems based on photonic chips have high scalability and stability, and are promising for further construction of global quantum communications networks. On-chip quantum light sources are a critical component of a fully integrated QKD system; especially a continuous-variable QKD (CV-QKD) system based on coherent detection, which has extremely high requirements for the light sources. Here, for what we believe is the first time, we designed and fabricated two on-chip tunable lasers for CV-QKD, and demonstrated a high-performance system based on these sources. Because of the high output power, fine tunability, and narrow linewidth, the involved on-chip lasers guarantee the accurate shot-noise-limited detection of quantum signals, center wavelength alignment of nonhomologous lasers, and suppression of untrusted excess noise. The system’s secret key rate can reach 0.75 Mb/s at a 50 km fiber distance, and the secure transmission distance can exceed 100 km. Our results mark a breakthrough toward building a fully integrated CV-QKD, and pave the way for a reliable and efficient terrestrial quantum-secure metropolitan area network.