Experimental observations of boundary conditions of continuous-time quantum walks

The continuous-time quantum walk(CTQW) is the quantum analogue of the continuous-time classical walk and is widely used in universal quantum computations. Here, taking the advantages of the waveguide arrays, we implement large-scale CTQWs on chips. We couple the single-photon source into the middle port of the waveguide arrays and measure the emergent photon number distributions by utilizing the fiber coupling platform. Subsequently, we simulate the photon number distributions of the waveguide arrays by considering the boundary conditions. The boundary conditions are quite necessary in solving the problems of quantum mazes.     

Estimation of photon counting statistics with imperfect detectors

The study on photon counting statistics is of fundamental importance in quantum optics. We theoretically analyzed the imperfect detection of an arbitrary quantum state. We derived photon counting formulae for six typical quantum states(i.e.,Fock, coherent, squeeze-vacuum, thermal, odd and even coherent states) with finite quantum efficiencies and dark counts based on multiple on/off detector arrays. We applied the formulae to the simulation of multiphoton number detections and obtained both the simulated and ideal photon number distributions of each state. A comparison between the results by using the fidelity and relative entropy was carried out to evaluate the detection scheme and help select detectors for different quantum states.     

XeCl准分子激光能量提取研究

在高功率准分子激光系统建设中,希望能获得较短的脉冲宽度和尽量多的激光能量。实验研究了不同注入水平下,脉冲时间间隔对脉冲链放大波形和放大器提取效率的影响;基于四能级速率方程和准分子反应动力学建立了准分子激光放大模型,计算了多种注入方式下种子光的放大过程,对关键参数给出了量化描述,得到与实验相符的计算结果。研究结果显示:脉冲序列间隔为9.3ns时,可获得约95%的连续注入情形下放大能量;对该准分子激光系统来讲,9.3ns是比较合适的脉冲间隔。     

Time-resolved measurement of atomic emission enhancement by fs--ns dual-pulsed laser-induced breakdown spectroscopy

Time-resolved measurement of atomic emission enhancement is performed by using a 500-fs KrF laser pulse incident upon a high density supersonic O_{2} gas jet, synchronized with an orthogonal ns frequency-doubled Nd:YAG laser pulse. The ultra-short pulse serves as an igniter of the gas jet, and the subsequent ns-laser pulse significantly enhances the atomic emission. Analysis shows that the contributions to the enhancement effect are made mainly by the bremsstrahlung radiation and cascade ionization.     

һά׼����ѹ�������ķ���

根据反向积分原理编写了流场反演程序,并开展了程序验证计算。在反演区域内,由临界面速度反演出与辐射流体力学程序MULTI计算结果几乎一致的结果;由Saturn加速器上实验测试的单个样品后自由面速度反演出了加载压强历史、多种厚度样品后自由面粒子速度历史等信息,与文献对比发现,反演结果与由加速器工作电流推出结果、WONDY程序计算结果、实验测试结果相吻合。本工作为即将开展的激光驱动准等熵压缩实验奠定了技术基础。     

Scheme for Robust Long-Distance Continuous Variable Quantum Key Distribution

It is shown that the configuration of phase coding for quantum key distribution with single photon can also be used for continuous variable quantum key distribution. Therefore the robust long-distance high-speed quantum key distribution can be achieved with current technology.     

基于局域操作下的两量子比特混态纠缠蒸馏实验研究

最大纠缠态在量子信息传输和处理过程中是最重要的资源之一，因此从退化的纠缠态中提炼出最大纠缠态一直是量子信息基础研究中的一个重要课题．根据Verstraete F等人在Phys．Rev．A，2001，64：010101（R）上提出的有效的方法，文章作者在实验上证明了基于局域操作下的两种形式的两量子比特混态纠缠蒸馏最佳协议．从原则上讲，文章的实验也可以容易地应用于任意两量子比特部分混合态的纠缠蒸馏．此外，作者还对经过蒸馏的第一类混合量子态进行Clauser-Home-Shimmony-Holt（CHSH）不等式的检测，以验证它的“隐藏非局域性”。     

局域密度矩阵与全局矩阵的相容条件

判断一组给定的正定的厄密矩阵,是否可以由一个多粒子的密度矩阵通过约化掉一些粒子后来得到的(相容问题)是一个非常重要的物理问题.它也是当前量子信息学中一个引起广泛关注的问题,它与多粒子纠缠有着密切的联系.我们给出了相容问题的一些必要条件.     

超短脉冲分布反馈染料激光器稳定工作条件分析

 利用耦合波理论，分析了一种作为KrF准分子激光MOPA系统的振荡源-亚皮秒超短脉冲分布反馈染料激光器（DFDL）的输出模式，指出实际的分布反馈染料激光器工作在单纵模状态是周期性增益调制的必然结果。数值模拟结果表明，DFDL输出光谱出现多条谱线的精细结构或调制现象，这是由多个顺序相干脉冲产生的。可以利用这种光谱调制现象来控制激光器的泵浦强度，获得稳定的单脉冲。光谱测量结果表明，在2倍泵浦阈值左右DFDL能够获得稳定的单模单脉冲输出。     

量子网络中任意两个网点间量子态的隐形传送

提出了在量子网络中任意两个网点间进行量子态的隐形传送的方案.在我们的方案中,应用了n个粒子的缠结态作为量子通道.对于非最大缠结态,我们讨论了量子态的几率隐形传送问题.