Security of continuous-variable measurement-device-independent quantum key distribution with imperfect state preparation

The state preparation operation of continuous-variable measurement-device-independent quantum key distribution (CV-MDI-QKD) protocol may become imperfect in practical applications. We address the security of the CV-MDI-QKD protocol based on imperfect preparation of the coherent state under realistic conditions of lossy and noisy quantum channel. Specifically, we assume that the imperfection of Alice's and Bob's practical state preparations equal to the amplification of ideal modulators and lasers at both Alice's and Bob's sides by untrusted third-parties Fred and Gray employing phase-insensitive amplifiers (PIAs), respectively. The equivalent excess noise introduced by the imperfect state preparation is comprehensively and quantitatively calculated by adopting the gains of PIAs. Security analysis shows that CV-MDI-QKD is quite sensitive to the imperfection of practical state preparation, which inevitably deteriorates the performance and security of CV-MDI-QKD system. Moreover, a lower bound of the secret key rate is derived under arbitrary collective attacks, and the upper threshold of this imperfection tolerated by the system is obtained in the form of the specific gains of PIAs. In addition, the methods presented will improve and perfect the practical security of CV-MDI-QKD protocol.     

The Improvement of Performance for Continuous-Variable Quantum Key Distribution with Imperfect Gaussian Modulation

Gaussian modulation is one of the key steps for the implementation of continuous-variable quantum key distribution (CVQKD) schemes. However, imperfection in the Gaussian modulation may introduce modulation noise that can deteriorate the performance of CVQKD systems. In this paper, we mainly investigate how to improve the performance of a CVQKD system from different aspects. First, we explore the several different origins, impacts and monitoring schemes for the modulation noise in detail. Then, we discuss the practical performance of a CVQKD system with an untrusted noise model and neutral party model, respectively. These analyses indicate that the neutral party model should be reasonably regarded as a general noise model, which will passively and greatly raise the performance of the system. Further, we propose a dynamic auto-bias control scheme to actively resist the modulation noise which comes from the drift of bias point of the amplitude modulator. Together these methods contribute to the improvement of the practical performance of CVQKD systems with imperfect Gaussian modulation.

     

离子色谱测定土壤中Cl-和SO2-4

介绍了离子色谱法测定土壤中Cl-和SO2-4的可行性以及相关的前处理方法,通过一定前处理方法,减少土壤中杂质对测定的干扰和对色谱柱的污染.有效选取提取液的种类和浓度及提取时间,准确测定了土壤中Cl-和SO2-4含量.Cl-和SO2-4的相对标准偏差分别为2.70%、2.89%,检出限分别为0.1950、0.2230μg·mL-1,平均回收率分别为106.7%,95.8%.方法简便,快速、灵敏度高.     

Multifunctional Small Molecule Fluorophore for Long‐Duration Tumor‐Targeted Monitoring and Dual Modal Phototherapy

In this work, a specific tumor‐targeted small molecular fluorophore for synchronous long‐duration cancer imaging, photodynamic therapy, and photothermal therapy is synthesized. This novel fluorophore exhibits specific targeting ability in certain tumors (U87MG, MDA‐MB‐231, A549, etc.) based on its inherent structure and efficiently generates local hyperthermia and reactive oxygen species simultaneously for imaging‐guided precise cancer therapy combining the photothermic and photodynamic effects under laser irradiation. Meanwhile, compared to traditional near infrared fluorophore, this novel fluorophore with significantly enhanced stability against photobleaching can prolong the time of tumor imaging and improve the phototherapy efficiency. This work presents a potential strategy to develop small‐molecule‐based cancer theranostic agents for simultaneous cancer targeting, imaging, and therapy.     

Alternative difference analysis scheme combining R‐space EXAFS fit with global optimization XANES fit for X‐ray transient absorption spectroscopy

Time‐resolved X‐ray absorption spectroscopy (TR‐XAS), based on the laser‐pump/X‐ray‐probe method, is powerful in capturing the change of the geometrical and electronic structure of the absorbing atom upon excitation. TR‐XAS data analysis is generally performed on the laser‐on minus laser‐off difference spectrum. Here, a new analysis scheme is presented for the TR‐XAS difference fitting in both the extended X‐ray absorption fine‐structure (EXAFS) and the X‐ray absorption near‐edge structure (XANES) regions. R‐space EXAFS difference fitting could quickly provide the main quantitative structure change of the first shell. The XANES fitting part introduces a global non‐derivative optimization algorithm and optimizes the local structure change in a flexible way where both the core XAS calculation package and the search method in the fitting shell are changeable. The scheme was applied to the TR‐XAS difference analysis of Fe(phen)₃ spin crossover complex and yielded reliable distance change and excitation population.     

一种基于高斯混合模型的改进EM算法研究

针对传统EM算法存在估计参数不具有最优性,以及在参数估计中需要人工参与等问题,提出一种基于高斯混合模型的改进EM算法。采用无人工参与的无监督思想,获取高斯混合模型对直方图拟合的最优参数组合。实验表明,该算法不仅能够快速地估计模型参量,而且能够给出最优参数,并在图像增强中使细节更明显,对比度更适中。     

Magnetically controllable resonance splitting in a unidirectional waveguide system with coupled cavities

A resonance splitting effect is investigated in a system composed of two cavities coupled by two unidirectional waveguides. Both theoretical analysis and numerical calculations demonstrate that the resonance splitting (indicating a coupling between the cavities) is independent of the phase shift between the cavities, which is in contrast to previous research where reciprocal waveguides are used. Moreover, this splitting can be tunable by an external magnetic field. Our findings offer a possibility to realize effective coupling between remote on‐chip resonators, which is highly demanded in the next‐generation photonic circuits.

     

环境卫星HJlA超光谱成像仪在轨辐射定标及光谱响应函数敏感性分析

环境卫星HJIA搭载的超光谱成像仪HSI是我国第一个对地观测的星载高光谱传感器,针对超光谱成像仪缺乏各通道光谱响应函数这一问题,对传统的反射率基法予以改进,提出一种不使用光谱响应函数的场地定标方法.利用敦煌场地2009年8月定标实验数据,实现超光谱成像仪在轨辐射定标.通过构建不同形状的光谱响应函数,分析光谱响应函数形状对最终辐射定标结果产生的误差.结果表明,利用新提出的场地定标方法可以实现超光谱成像仪绝对辐射定标,除水汽和氧气吸收通道外,光谱响应函数对定标结果的影响小于3%,采用新定标方法得到的定标系数可以满足应用的需求.     

蒸汽喷射器变工况性能的CFD探讨

利用二维轴对称,真实气体模型对喷射式制冷空调系统的喷射器进行CFD计算。真实气体模型占用较多的计算机资源,但它的计算结果更加真实。计算的目的在于得到在变工况条件下喷射器性能的变化和制冷系统性能的变化情况。在计算范围中,存在一最优的发生压力Pg*(3.973568bar),使得此时的喷射系数和系统COP最大。当Pg>Pg*时,喷射系数和COP随着发生压力的增加而减少;当Pg相似文献   

高温超导电缆直流测试电源平台的搭建

根据高温超导电缆测试用直流电源平台的要求,建立了硬件平台。该平台为模块化结构,具有输出精度高,便于扩展等特点;为方便操作,建立了基于LabVIEW的软件平台,对直流电源平台进行远程控制,并给出了远程控制的程序流程图,实现了电流的匀速上升和下降以及上升过程中的中断操作;利用该电源平台进行了超导电缆的临界电流测试实验,验证了直流电源平台符合高温超导电缆的测试要求。