Multiparty Quantum Cryptographic Protocol

We propose a multiparty quantum cryptographic protocol. Unitary operators applied by Bob and Charlie, on their respective qubits of a tripartite entangled state encoding a classical symbol that can be decoded at Alice＇s end with the help of a decoding matrix. Eve＇s presence can be detected by the disturbance of the decoding matrix. Our protocol is secure against intercept resend attacks. Furthermore, it is eifficient and deterministic in the sense that two classical bits can be transferred per entangled pair of qubits. It is worth mentioning that in this protocol, the same symbol can be used for key distribution and Eve＇s detection that enhances the etfficiency of the protocol.     

A new approach to the theory of relativity. II. The general theory of relativity

The considerations of Part I are extended and the experimental data and hypotheses that led to the establishment of the general theory of relativity are analyzed. It is found that one of the fundamental assumptions is that light is propagated homogeneously; i.e., by using arbitrary systems of coordinates, propagation of light can be represented by a homogeneous quadratic form. This is shown to be an assumption that can be verified by experiment, at least in principle. As a result of adding a number of further assumptions to this, the usual formalism of the general theory of relativity can be established. In the above point of view, the general theory of relativity—like any other theory—cannot be built upad hoc, but is built on distinct physical hypotheses, each of which can be subjected to test by experiment.     

多光子非线性过程中的振幅平方压缩

本文研究了多光子非线性光学过程中的振幅平方压缩,证明了K光子么正算符Sk(z)(K>2)对非真空相干态的作用在—级近似下会产生振幅平方压缩.以及Sk(z)(K>2,K≠4)对真空态的作用不会产生振幅平方压缩.发现4个光子么正算符S4(z)对真空态的作用可以产生振幅平方压缩,这表明振幅平方压缩是一种独立于二阶压缩、反聚束以及亚泊松统计分布的新的光场非经典效应.     

任意相位差条纹信号细分方法的研究

为消除传统细分方法中由于两路条纹信号不正交引入的细分误差，提出了一种可对任意相位差条纹信号直接细分的新方法。根据两路条纹信号的极性和幅值大小，把一个信号周期分成8个区段。高速采集两路条纹信号，通过判断信号采样点所处的区段是否跳变对信号幅值交点进行动态跟踪。对不足一个周期的条纹移动，当测量出起点与终点的幅值，计算出其所在的区段及位置后，结合两路信号的交点，可实现对任意相位差条纹信号的细分。实验结果表明，该方法突破了传统细分方法必须信号正交的限制，可对任意相位差信号进行准确地细分，降低了条纹测量中器件安装与调试的难度，具有更强的环境适应性和抗干扰能力。     

梯度耦合下神经元网络中靶波和螺旋波的诱发研究

神经系统内数量众多的神经元电活动的群体行为呈现一定的节律性和自组织性. 当网络局部区域存在异质性或者受到持续周期性刺激, 则在网络内诱发靶波, 且这些靶波如'节拍器'可调制介质中行波的诱发和传播. 基于Hindmarsh-Rose 神经元模型构造了最近邻连接下的二维神经元网络, 研究在非均匀耦合下神经元网络内有序波的诱发问题. 在研究中, 选定网络中心区域的耦合强度最大, 从中心向边界的神经元之间的耦合强度则按照阶梯式下降. 研究结果表明, 在恰当的耦合梯度下, 神经元网络内诱发的靶波或螺旋波可以占据整个网络, 并有效调制神经元网络的群体电活动, 使得整个网络呈现有序性. 特别地, 当初始值为随机值时, 梯度耦合也可以诱发稳定的有序态. 这种梯度耦合对网络群体行为调制的研究结果有助于理解神经元网络的自组织行为.     

Dynamics of molecular alignment steered by a few-cycle terahertz laser pulse

The field-free alignment of molecule ClCN is investigated by using a terahertz few-cycle pulse (THz FCP) based on the time-dependent density matrix theory. It is shown that a high degree of molecular alignment can be obtained by changing the matching number of the THz FCPs in the adiabatic regime and the non-adiabatic regime. The matching number can affect both the maximum value of the alignment and the time at which it is achieved. It is also found that a higher degree of alignment can be achieved by using the THz FCP at lower intensity and there exists an optimal threshold of molecular alignment with the increase of the field amplitude. Also found is the frequency sensitive region in which the degree of maximum alignment can be enhanced greatly by modulating the center frequencies of different THz FCPs. The investigation demonstrates that comparing with a THz single-cycle pulse, a better result of the field-free alignment can be created by a THz FCP at a constant rotational temperature of molecule.     

A novel system of the simultaneous trapping of dark-bright solitons within a nano-waveguide system

We propose a novel system of a nano-waveguide that can be used to generate the continuous spectrum, i.e. white light. The simultaneous trapping and generation of short and millimeter waves can also be performed by using either bright or dark soliton. A system consists of two micro- and a nano-ring resonators that can be integrated into a single system. The large bandwidth is generated by a soliton pulse within a Kerr-type nonlinear medium where the continuous bandwidth or wavelength can be performed. The simultaneous dark-bright solitons conversion is performed and achieved. Results obtained have shown the potential of using the technique for continuing light spectra generation, where the filtering signals are allowed by using the suitable device parameters. The advantage is that the large bandwidth separation of the short and sub-millimeter waves can be obtained, which is allowed to form the simultaneous generation of short and millimeter waves within a single system. Further, light pulse can be trapped within a nano-waveguide, which is available to form the memory device.     

磁梯度张量不变量的椭圆误差消除方法研究

基于磁梯度张量不变量定位方法, 可以实现对目标的单点实时定位, 且定位目标不限于静止目标, 这一方法目前得到了人们的广泛关注, 但该方法由于存在着椭圆系数导致目标定位误差较大的问题. 针对该问题, 提出了一种基于正六面体磁梯度张量测量系统的单点实时定位改进方法, 该方法通过消除原定位方法中不变量存在的椭圆系数, 从而克服椭圆误差对定位精度的影响. 具体做法是通过求解测量系统中正六面体的六个平面中心点处磁梯度张量的特征值, 并把这些特征值按照一定关系进行组合来消除椭圆系数, 来获得六个平面的新不变量, 再对这些新不变量求其梯度值, 根据这些梯度值对目标进行定位, 这样该定位方法可以有效的克服椭圆误差, 可对目标进行单点实时定位. 对改进定位方法进行了仿真实验分析, 结果表明改进方法可以实现目标的单点实时定位, 定位的平均相对误差较现有方法减少10.9%. 改进方法对所搭载平台的机动性要求较低, 其平台可做直线或曲线运动对目标实现单点实时定位.     

基于光电双测头技术的液位监测系统设计

阐述了一种利用光电检测方法对透明容器内的液位进行监控的系统设计。系统利用激光平行于液面射入后被凹液面反射的光学现象实现了非接触式测量。实验证明该系统抗干扰能力强,具有良好的稳定性,监测误差仅为0．30%,能广泛应用于医疗、工业、家电等领域。     

Dynamic stiffness method for exponentially varying harmonic excitation of continuous systems

The dynamic stiffness method relating the amplitudes of applied forces and responses of a harmonically vibrating continuum has received wide attention. It enables the infinite number of natural modes to be represented by a finite number of nodal co-ordinates for continuous structures of beams and folded plates. However, the method has been applied almost exclusively to harmonic, or periodic, oscillations. This is due mainly to the rather misleading intuition that only harmonic vibrations can be described by solutions with separate time- and space-dependent factors. It is shown here that a much wider class of problem of exponentially varying harmonic excitations can also be analyzed by the dynamic stiffness method. The extension is achieved simply by using complex frequency parameters. The forced response (that is, the part of the response which is independent of the initial conditions) can be obtained directly by solution of linear equations. A single degree of freedom system is considered first, as an illustrative example. It is shown that the present method is equivalent to the usual Duhamel integral method except that integration is completely avoided and the transient effects due to the initial conditions can be considered separately. The method is then applied to undamped straight beam members and is modified so that damped vibration can be covered as well. Distributed loads are then considered and explicit formulae are introduced. Finally, for completeness of presentation, the responses are compared with those obtained by using modal analysis. The method is proved to be equivalent to modal analysis and has the advantages over the latter that (i) integrations in the time variable are completely avoided; (ii) the forced response can be obtained directly; (iii) decomposition into generalized forces is not required; and (iv) the force-response relation is easily visualized.     

THz frequency bands generation for Radio-over-Fiber systems

We propose a new design THz frequency for Radio-over-Fiber (RoF) systems that use the dense wavelength division multiplexing wavelength enhancement, whereas the increasing in channel capacity and signal security can be provided. The increasing in number of channel can be obtained by the increasing in wavelength density, while the security is introduced by the specific wavelength filter, which is operated by the central operator. The optical communication wavelength enhancement is reviewed. The advantage is that the proposed system can be implemented and used incorporating with the existed communication link in both wire and terabit wireless communication system.     

Canny算法的改进及其硬件的实现

传统的Canny边缘检测算法是先对图像进行平滑,然后利用二维滤波器计算图像的梯度值,从而得到梯度直方图。通过基于梯度直方图来选取双阈值,最后进行基于双阈值的非极大值抑制,得到边缘检测的图像。为了能很方便地在硬件中实现这种算法,对传统的Canny算法进行了适当的改进,利用模板来代替原算法中的卷积,从而使得该算法在FPGA(Field Programmable Gate Array)中可以完全利用原理图来实现。     

基于渐变折射率光量子阱的密集波分复用研究

提出了利用渐变折射率光量子阱设计密集波分复用器件的构想,用时域有限差分法验证了该构想的可行性,分析了这种器件工作的物理机理.计算表明,折射率分布曲线不同的光子阱能局域不同的量子态,应用不同局域态的光量子阱对光波进行合成和分离,能够有效减小信道间隔,实现密集波分复用功能,使有限的频带能容纳更多的信道,提高频谱利用率.该器件信道中心波长精确稳定,信道隔离度较大,插入损耗小而均匀,信道间信号串扰小.     

Analytical description of cross-phase modulation in dispersive optical fibers

The effect of intensity distortion induced by cross-phase modulation in dispersive optical fibers is studied. It is shown that, in most configurations in which distortions that are due to cross-phase modulation can become significant to optical communications, the effect of cross-phase modulation can be described with excellent accuracy by simple analytical expressions. The presented analysis also suggests that intensity distortions owing to cross-phase modulation can be efficiently reduced by linear dispersion compensation.     

基于叠栅技术的二维亚波长周期结构成像设计

用光子学方法研究了叠栅技术中,当试件光栅被拉压和旋转后,叠栅条纹的空间周期和相对于基准光栅的取向,试件光栅被拉压后的节距等相关问题。根据衍射光波的空间周期可能大于试件光栅空间周期的特点,对二维亚波长周期结构衍射成像进行了设计研究。首先,对二维亚波长周期结构衍射物进行编码,以获得包含编码光栅空间信息的均匀波;其次,使编码得到的均匀波通过光学系统,并被放大到CCD相机所能辨识的大小;再次,经解码光栅解码,滤掉编码波,最终获得二维亚波长周期结构物的空间结构信息,达到超分辨的目的。同时,对成像过程进行了较为详尽的分析,对编码器、解码器的位置以及它们相对衍射物的取向进行了设计研究,对滤波器的选择给予了必要的说明,指出了取得超分辨成像的关键。     

一维亚波长周期结构物成像的光子学研究

当用波长为λ的单色平行光垂直照射到光栅常数d<λ的亚波长周期结构衍射物时,会产生隐失波。由于快速衰减,这种亚波长周期物是不能成像的。但是,通过对亚波长周期结构物进行适当的编码后可得到均匀波,使这种携带了隐失波信息的均匀波通过经特别设计的光学系统并被放大到CCD所能识别的像素大小后,再进行必要的解码以滤掉编码波,即可得到原亚波长周期结构衍射物的像,最终达到超分辨的目的。基于这种新颖的成像技术,用常规仪器就实现了对亚波长周期结构物的成像。在运用光子学方法对实验和成像过程进行较为详尽的理论分析的同时,对编码器、解码器的位置以及它们相对物光栅的取向给出了设计性研究,对滤波器的选择给予了必要的说明。实验结果验证了该设计理论的正确性。     

铁磁、肖特基金属和半导体纳米自旋过滤器中的量子尺寸效应

采用转移矩阵法,研究了结构尺度对自旋过滤器中电子自旋极化特性的影响．该自旋过滤器可以通过在半导体异质结上沉积纳米尺度的铁磁条带和肖特基金属条带来实现．计算结果表明,电子的自旋极化特性强烈依赖于铁磁条带和肖特基金属条带的结构尺度和位置,即该器件中存在量子尺寸效应．此外,我们的计算结果还表明,电子的自旋极化特性还与施加在肖特基金属条上的电压所诱发的电垒高度密切相关．因此,我们可以通过改变施加在肖特基金属条上的电压来调控该器件中电子的自旋极化特性,制造一个电压可调的电子自旋过滤器．     

CFD-DEM simulation of three-dimensional aeolian sand movement

A three-dimensional CFD-DEM model is proposed to investigate the aeolian sand movement.The results show that the mean particle horizontal velocity can be expressed by a power function of heights.The probability distribution of the impact and lift-off velocities of particles can be described by a log-normal function,and that of the impact and lift-off angles can be expressed by an exponential function.The probability distribution of particle horizontal velocity at different heights can be described as a lognormal function,while the probability distribution of longitudinal and vertical velocity can be described as a normal function.The comparison with previous two-dimensional calculations shows that the variations of mean particle horizontal velocity along the heights in two-dimensional and three-dimensional models are similar.However,the mean particle density of the two-dimensional model is larger than that in reality,which will result in the overestimation of sand transportation rate in the two-dimensional calculation.The study also shows that the predicted probability distributions of particle velocities are in good agreement with the experimental results.     

自由电子激光的预群聚

研究了自由电子激光预群聚产生的辐射,表明预群聚不仅可以提高效率而且使低增益得到增强,从而在理论上解释了由射频直线加速器驱动的自由电子激光预群聚器(prebuncher)的作用。同时还指出,预群聚有在不增加电子束能量情况下缩短激光波长和降低对电子束质量要求等作用。     

三量子比特纠缠Greenberger-Horne-Zeilinger态和W态的量子线路实现

两个简单的量子线路被提出分别用来制备三量子比特Greenberger-Horne-Zeilinger(GHZ)态和W态。众所周知,任意的多量子比特门都可以由受控非门和单量子比特门复合而成。同样,我们发现三量子比特GHZ态和W态也可以由受控非门和单量子比特门来制备。因此,从量子计算的角度来看我们的方案十分重要。由于在整个过程只用到了单量子比特操作和双量子比特操作,所以我们的方案在实验中很容易实现。