GaN基量子点结构的喇曼特征

采用量子力学的微扰理论，对GaN基量子点结构的喇曼频移进行分析。在喇曼实验中，观察InGaN／GaN量子点结构的E2和A1(LO)的模式，并发现实验中样品的喇曼频移与GaN的体材料相比，有着明显的红移。     

二粒子态控制双向量子隐形传态（英文）

为实现二粒子态的控制双向量子隐形传态,基于张量分析、贝尔基测量和冯·诺依曼测量等方法,提出二粒子态控制双向量子隐形传态的通道准则,准则中,选择九粒子纠缠态为量子通道,并给出任意九粒子纠缠态能否作为量子通道的必要条件.基于该条件,控制者完成冯·诺依曼测量后,通道被分为单通道、双通道、三通道和四通道.以双通道为例进行计算分析,在Alice、Bob和Controller的共同作用下,经冯·诺依曼测量后进行贝尔基测量和对应的幺正变换,最终实现Alice和Bob之间量子态的交换,通过双通道的隐形传输,验证了所提准则的可行性并给出量子通道选择的一般方法.     

低温下ZnSe-ZnS多量子阱的光致发光光谱和喇曼散射谱

本文报导了2K下,在GaAs(100)衬底上用MOCVD方法生长的ZnSe-ZnS多量子阱材料的光致发光光谱和喇曼散射谱.用共振激发、共振喇曼和共振瑞利散射等方法对各发光谱带和喇曼散射峰的来源和机制进行了鉴别.     

利用Raman相互作用实现未知原子态的传输

利用Λ型三能级原子与单模腔场之间的相互作用,研究简并喇曼相互作用过程中产生场-原子最大纠缠态的方法,实现量子逻辑门的方法,以及如何利用这种方法来实现未知原子态的量子隐形传送.     

低温下ZnSe－ZnS多量子阱的光致发光光谱和喇曼散射谱

本文报导了２Ｋ下，在ＧａＡｓ（１００）衬底上用ＭＯＣＶＤ方法生长的ＺｎＳｅ－ＺｎＳ多量子阱材料的光致发光光谱和喇曼散射谱．用共振激发、共振喇曼和共振瑞利散射等方法对各发光谱带和喇曼散射峰的来源和机制进行了鉴别．     

RLC介观电路的量子化研究

通过正则变换,应用费恩曼路径积分方法,得出了RLC介观电路的严格波函数,并进一步讨论了电路中电荷和广义电流的量子涨落.     

等待量子模拟革命的到来

<正>量子计算机最令人期待的用途之一,是作为开发新药、催化剂和材料的工具。它可以精确地模拟"化学物质"和"材料"的量子结构以及行为。但是材料科学家和化学家们警告说,量子机器远未能与当今日益强大的经典模拟方法竞争。技术产生的短期影响目前正被过度炒作。专家认为,聪明的设计选择,最终会让量子机器与经典计算机协力,实现效益最大化。量子计算机使用量子位或量子比特,它可     

费恩曼与量子计算机

介绍了费恩曼对计算机科学的思考、费恩曼量子计算机理论以及北航在量子信息领域的研究.费恩曼曾做过一系列关于量子计算机科学的演讲,提出通过量子机制可在原子尺度上实现通用计算机,开创了量子计算机和纳米科技等领域.     

利用五粒子簇态实现四粒子态的量子隐形传态

主要研究了运用五粒子簇态作为量子通道来实现特殊形式的四粒子态的量子隐形传态方案.该方案运用了量子力学中量子纠缠的理论.在这个方案中,发送者只需要进行五粒子冯·诺依曼投影测量,接收者根据发送者的测量结果,通过在其量子位上执行一些适当的幺正变换得出原始的四量子比特状态.提出的这个方案可以很好地应对一般的窃听方式.     

量子物理学难懂吗?──介绍《伯克利物理学教程》第四卷:《量子物理学》

量子物理学是二十世纪初发展起来的新学科,它主要研究的是微观粒子的运动.由于它提出了一些新概念,与我们大家比较熟悉的经典物理概念相差很大,有很多论点被认为难以理解,因而成为初学者的困难.真是这么难吗? “我不相信学习量子物理学比学习物理学其它部分在实质上会更困难”,一位美国教授E.H.威切曼这么说.他编写了一本教科书《量子物理学──伯克利物理学教程第四卷》,现已由复旦大学物理系译成中文出版. 威切曼在序言中指出,过去许多人认为量子物理学“神秘”的原因有两个:一是“经典观点的成见”;一是“实验图象不完整”.他认为,今天…     

LETTER: Entropy Using Path Integrals for Quantum Black Hole Models

Canonical quantum gravity has been used in the search for eigenvalue equations that could describe black holes. In this paper we choose one of the simplest of these quantum equations to show how the usual Feynman's path integral approach can be applied to get the corresponding statistical properties. We get a logarithmic correction to the Bekenstein–Hawking entropy as already obtained by other authors by other means.     

Magnetoconductance oscillations in semiconductor-superconductor junctions with a laterally isolating barrier layer inside semiconductor region

The oscillatory characteristics of magnetoconductance for a junction composed of a superconductor and a semiconductor, in which two parallel quantum wave guides are coupled with each other through a potential barrier layer, are studied systematically. To model the imperfectness of the interface, we introduce a function scattering potential barrier lying close to the interface of the junction. The magnetoconductance oscillations (MCO) in this system stem from two sources: one is the interference of wave functions of quasi-particles due to multiple Andreev reflections at the interface; the other is attributed to the variation of the number of the propagation modes when introducing the isolating barrier layer. The introduction of the isolating layer in the quantum wave-guides strongly modifies MCO. We also present a physical picture for the MCO based on a phenomenological argument. The theoretically fitted results are in good agreement with numerical ones.Received: 21 March 2003, Published online: 4 August 2003PACS: 73.40.-c Electronic transport in interface structures - 74.80.Fp Point contact; SN and SNS junctions - 73.21.Hb Quantum wires - 85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)     

A path-probability representation for wavefunctions

A mathematical representation of the quantum mechanical wavefunction in terms of path-probability is presented. It provides an interesting reformulation of Feynman's path-integrals. The whole results are natural consequences of stochastic calculus of variations.     

The Schrödinger equation in quantum field theory

Some aspects of the Schrödinger equation in quantum field theory are considered in this article. The emphasis is on the Schrödinger functional equation for Yang-Mills theory, arising mainly out of Feynman's work on (2+1)-dimensional Yang-Mills theory, which he studied with a view to explaining the confinement of gluons. The author extended Feynman's work in two earlier papers, and the present article is partly a review of Feynman's and the author's work and some further extension of the latter. The primary motivation of this article is to suggest that considering the Schrödinger functional equation in the context of Yang-Mills theory may contribute significantly to the solution of the confinement and related problems, an aspect which, in the author's opinion, has not received the attention it deserves. The relation of this problem with certain others such as those of quarks, superconductivity, and quantum gravity is considered briefly, together with certain basic aspects of the formalism that may be of interest in their own right, especially for the beginner.Dedicated to Professor Fritz Rohrlich on the occasion of his seventieth birthday, May 12, 1991.     

Orbital restriction on the functional form of the Lagrangian

The fact that a non-relativistic particle describes an orbit imposes a restriction on the functional form of the Lagrangian. For a classical particle subjected to an arbitrary local ‘generalized force,’ the (local) Lagrangian is shown to involve, at highest, first, second and third time-derivatives of the position respectively, in one, two and three dimensions. The generalization in the quantum régime is indicated with the aid of Feynman's path integrals.     

On the quantum Hamilton-Jacobi formalism

Some postulates are introduced to go from the classical Hamilton-Jacobi theory to the quantum one. We develop two approaches in order to calculate propagators, establishing the connection between them and showing the equivalence of this picture with more known ones such as the Schrödinger's and the Feynman's formalisms. Applications of the above-mentioned approaches to both the standard case of the harmonic oscillator and to the harmonic oscillator with time-dependent parameters are made.     

Relativistic generalization and extension to the non-Abelian gauge theory of Feynman's proof of the Maxwell equations

R. P. Feynman showed F. J. Dyson a proof of the Lorentz force law and the homogeneous Maxwell equations, which the obtained starting from Newton's law of motion and the commutation relations between position and velocity for a single nonrelativistic particle. We formulate both a special relativistic and a general relativistic versions of Feynman's derivation. Especially in the general relativistic version we prove that the only possible fields that can consistently act on a quantum mechanical particle are scalar, gauge, and gravitational fields. We also extend Feynman's scheme to the case of non-Abelian gauge theory in the special relativistic context.     

隔离层厚度和盖层厚度对InAs/GaAs量子点应变分布和发射波长的影响

分析了量子点盖层生长过程中隔层厚度对应变分布的影响,指出隔层材料的纵向晶格常数与量子点材料的纵向晶格常数对应变分布具有重要意义.定性说明了应变因素在隔离层生长过程中对量子点高度塌陷产生的影响.讨论了当隔离层顶面与量子点高度持平后,增加盖层厚度对应变分布的影响.基于变形势理论,讨论了上述几何参数的变化对发光波长的影响,并与实验结果进行了对比.结果表明,在量子点加盖过程中,应变因素对其形貌和发光特性具有重要作用,以应变工程为基础的发射波长调控是拓展量子点波长发射范围的有效途径. 关键词： 应变工程 半导体量子点 隔离层 盖层     

Alternating layer and island growth of Pb on Si by spontaneous quantum phase separation

Real-time in situ x-ray studies of continuous Pb deposition on Si(111)-(7x7) at 180 K reveal an unusual growth behavior. A wetting layer forms first to cover the entire surface. Then islands of a fairly uniform height of about five monolayers form on top of the wetting layer and grow to fill the surface. The growth then switches to a layer-by-layer mode upon further deposition. This behavior of alternating layer and island growth can be attributed to spontaneous quantum phase separation based on a first-principles calculation of the system energy.