Quantum Gate Operations in Decoherence-Free Subspace with Superconducting Charge Qubits inside a Cavity

We propose a feasible scheme to achieve universal quantum gate operations in decoherence-free subspace with superconducting charge qubits placed in a microwave cavity. Single-logic-qubit gates can be realized with cavity assisted interaction, which possesses the advantages of unconventional geometric gate operation. The two-logic- qubit controlled-phase gate between subsystems can be constructed with the help of a variable electrostatic transformer. The collective decoherence can be successfully avoided in our well-designed system. Moreover, GHZ state for logical qubits can also be easily produced in this system.     

图像跟踪系统中机动目标预测的实现

针对装甲车上的图像跟踪系统，提出一种机动目标预测方法。将目标的运动分解为2部分，即全局运动和局部运动，并根据各自的动态特性分别进行预测。文章以局部运动预测为重点，通过对机动目标跟踪技术的研究，建立起性能优良的跟踪滤波器，并将其扩展到预测滤波器中对目标的未来运动状态进行预测，从而提出“交互式多模型预测算法”，并对该算法进行仿真，给出速度均方根误差的仿真结果。仿真结果表明:该算法预测精度高、自适应能力强。最后还给出了预测门的计算方法。     

利用单个三粒子最大GHZ态或两个EPR态隐形传送任意三粒子GHZ态

提出利用单个三粒子最大Greenberger-Horne-Zeilinger (GHZ)态或两个Einstein-Podolsky-Rosen (EPR)态作为量子信道确定性隐形传送任意三粒子GHZ态的两个方案，并将方案推广至隐形传送任意n(n≥4)粒子GHZ态的情况.讨论了量子信道受噪声影响时隐形传态的保真度.研究发现，当作为量子信道的单个三粒子最大GHZ态受到噪声影响时，隐形传态的保真度仅与量子信道的纠缠度有关，而当作为量子信道的两个EPR态受到噪声影响时，隐形传态的保真度不仅与量子信道的纠缠度有关，还与待传送态的纠缠度有关.所提出的方案具有节省量子信道纠缠资源的特点. 关键词： 隐形传态 三粒子Greenberger-Horne-Zeilinger态 量子逻辑门 保真度     

杨振宁教授谈怎样学科学——对香港中学生的一次讲话

 首先,我想同大家讨论科学中的实验技能间题.对人类来说,科学毕竟有百分之九十是实验活动,科学的基础是实验.那些特别擅长动手的学生应该把握住自己的优势.因为他们凭这种本领往往超过他人,在某些适当的科学领域中做最有益和最重要的事情.我想强调一下,一个人的动手能力是一种天赋,因人迥异.我给大家讲讲我和我的儿子遇到的一件事.有一天,我们停车房的门推手坏了.我们俩爬上梯子,想查看一下停车房顶部的装置,哪里出了毛病.我们刚爬到那儿,他便说是一个小轮齿错位了.     

关于ι—群的半单结构的几点注记

设G是一个ι-群,R（G）是文献[1]意义下的G的根。本文通过R（G）的刻划,获得了R（G）的若干特征性质,并由此推广了文献[1]中有限值ι-群的半单结构定理（定理3.4）。     

开关型Logistic模型

基于界壳理论,将界门的开关作用引入到Logistic模型中,建立了一个新的离散Logistic模型,对模型进行了映射计算,分析了在不同参数下模型的非线性特征,计算得出了若干常定数和循环小数。     

基于门冻结技术的无冒险RS触发器设计

数字电路中的冒险现象不仅会导致电路的误操作,而且消耗了很多能量、增加了操作时间,因此在电路设计中冒险的检测和消除非常重要．文章介绍了门冻结技术的基本思想,以此为基础给出了基于F门的CMOS与非门、或非门的逻辑单元电路设计,并将其应用到RS触发器的设计中,经PSPICE模拟显示,与传统的同步RS触发器相比,所设计的基于F门的同步RS触发器电路不仅具有正确的逻辑功能,消除了冒险,而且使电路的功耗也得到了有效地降低。     

Hot-carrier degradation for 90nm gate length LDD-NMOSFET with ultra-thin gate oxide under low gate voltage stress

The hot-carrier degradation for 90~nm gate length lightly-doped drain (LDD) NMOSFET with ultra-thin (1.4~nm) gate oxide under the low gate voltage (LGV) (at V_g=V_th, where V_th is the threshold voltage) stress has been investigated. It is found that the drain current decreases and the threshold voltage increases after the LGV (V_g=V_th stress. The results are opposite to the degradation phenomena of conventional NMOSFET for the case of this stress. By analysing the gate-induced drain leakage (GIDL) current before and after stresses, it is confirmed that under the LGV stress in ultra-short gate LDD-NMOSFET with ultra-thin gate oxide, the hot holes are trapped at interface in the LDD region and cannot shorten the channel to mask the influence of interface states as those in conventional NMOSFET do, which leads to the different degradation phenomena from those of the conventional NMOS devices. This paper also discusses the degradation in the 90~nm gate length LDD-NMOSFET with 1.4~nm gate oxide under the LGV stress at V_g=V_th with various drain biases. Experimental results show that the degradation slopes (n) range from 0.21 to 0.41. The value of n is less than that of conventional MOSFET (0.5-0.6) and also that of the long gate length LDD MOSFET (\sim0.8).     

Electronic transport properties of metallic single-walled carbon nanotubes

We have calculated the differential conductance of metallic carbon nanotubes by the scatter matrix methon.It is found that the differential conductance of metallic nanotube-based devices oscillates as a function of the bias voltage between the two leads and the gate voltage.Oscillation period T is directly proportional to the reciprocal of nanotube length.In addition,we found that electronic transport properties are sensitive to variation of the length of the nanotube.     

基于陷门搜索的条件代理重加密方案

为实现对数据细粒度且可扩展的访问控制,通过引入陷门搜索实现快速的条件匹配,提出一个高效的、可用于多条件以及"与"和"或"的复杂组合条件的代理重加密方案,较大地提高了条件代理重加密的效率,可实现高效的按需授权和撤销操作以满足用户对数据的细粒度访问控制需求.同时还引入强一次性签名算法以保证加密过程的安全性,最后在随机预言机模型下证明其在3-QDBDH假设下可抵抗选择密文攻击.