GeSi量子点的发光特性研究

研究了在Si衬底上自组织生长Ge岛或Ge量子点的光致发光特性，用原子力显微镜(AFM)和透射电子显微镜(TEM)观察Ge岛的大小和密度，经过680℃退火30min，观察到了量子点的光致发光。     

Hybrid LSDA/Diffusion Quantum Monte-Carlo Method for Spin Sequences in Vertical Quantum Dots

We present an new hybrid Diffusion Quantum Monte-Carlo (DQMC)/Local Spin Density Approximation (LSDA) method, to compute the electronic structure of vertical quantum dots (VQD). The exact many-body electronic configuration is computed with a realistic confining potential. Our model confirms the atomic-like model of 2D shell structures obeying Hund's rule already predicted by LSDA.     

氧化物薄膜抑制量子点的光衰性能

量子点应用于LED中,可获得高饱和性、宽色域光源,在液晶显示背光源领域前景广阔。但是,影响量子点寿命的因素很多,如温度、水氧等,严重阻碍了其推广应用。目前,水氧对量子点光衰性能影响的研究较少,本文旨在研究无机氧化物薄膜阻隔层对量子点光衰性能的影响。量子点成膜后表面溅射Al2O3、SiO2水氧隔离薄膜,蓝光LED激发绿光量子点,研究其光衰性能。结果表明,与无隔离膜的样品相比,单层SiO2薄膜的样品光衰性能有所改善;双层的SiO2薄膜及SiO2/Al2O3复合薄膜,可以有效地减小薄膜孔洞大小和孔洞密度,阻隔水氧的进入,抑制量子点的光衰减,提高量子点寿命。     

Numerical Calculation of Electronic Structure for Three-Dimensional Nanoscale Semiconductor Quantum Dots and Rings

In this paper the electronic structure of nanoscale ellipsoid-torus-shaped semiconductor quantum dot and quantum ring is investigated of utilizing a unified model. This three-dimensional model considers the effective one-band Hamiltonian, the position- and energy-dependent effective mass approximation and Landé factor, the finite hard wall confinement potential, and the Ben Daniel-Duke boundary conditions. It is solved numerically without any fitting parameters by using a computationally cost effective nonlinear iterative method. It is found that the penetration of magnetic fields into non-simply connected topology of structures leads to substantial difference in the transition energy between InAs/GaAs quantum dot and quantum ring. The quantum ring exhibits non-periodical electron-hole transition energies when the magnetic field increases. Contrary to the one-dimensional periodical argument on the ring's energy spectra, our examination into the nanoscale semiconductor quantum ring agrees with the experimental result. The energy band gap of quantum dot is an increasing function of the magnetic field. For quantum rings the energy band gap oscillates non-periodically and the oscillation period is strongly controlled by the inner radius of structures. The magnetization of quantum ring not only jumps non-periodically but also saturates eventually when the magnetic field increases.     

Optical and Electrical Properties of Colloidal Quantum Dots in Electrolytic Environments: Using Biomolecular Links in Chemically-Directed Assembly of Quantum Dot Networks

The threshold of the absorption spectra of colloidal cadmium sulfide (CdS) quantum dots in electrolytic solutions is shown to shift as the concentration of the electrolyte is varied. The shift in the absorption threshold as a function of the electrolytic concentration is given by electrolytic screening of the field caused by the intrinsic spontaneous polarization of these würtzite quantum dots. These electrolyte-dependent absorption properties are compared with Fermi-level tuning in carbon nanotubes in electrolytic environments.Moreover, concepts for integrating such colloidal quantum dots in high density networks with biomolecular links are discussed. Such biomolecular links are used to facilitate the chemically-directed assembly of quantum dots networks with densities approximating 10¹⁷ cm⁻³.     

Design and Application of Micro-Spectrometer Based on Quantum Dots Photodetector

Abstract

In this article, a micro-spectrometer was developed based on quantum dots photodetector. The quantum dots photodetector has higher sensitivity than CCD, and its photoconduction gain has achieved 1.11E8 under 0.01 picowatt irradiation at liquid nitrogen temperature. In addition, the quantum dots micro-spectrometer is coupled to the microscopic imaging spectrometer to form a dual-model microscopic imaging spectrometer, which carries out spectral collection and comparison of biological samples. The experimental results show that the transmission spectra of rat skin obtained by the dual-model microscopic imaging spectrometer are consistent, and the comparison and verification of the two spectral measurement systems are realized.     

Towards Fully Quantum Mechanical 3D Device Simulations

We present a simulator for calculating, in a consistent manner, the realistic electronic structure of three-dimensional heterostructure quantum devices under bias and its current density close to equilibrium. The electronic structure is calculated fully quantum mechanically, whereas the current is determined by employing a semiclassical concept of local Fermi levels that are calculated self-consistently. We discuss the numerical techniques employed and present illustrative examples that are compared with quantum transport calculations. In addition, the simulator has been used successfully to study shape-dependent charge localization effects in self-assembled GaAs/InGaAs quantum dots.     

Fano Resonance Through Quantum Dots in Tunable Aharonov-Bohm Rings

Stimulated by recent intriguing experiments with a quantum dot in an Aharonov-Bohm (AB) ring, we investigate novel resonant phenomena by studying the total transmission probability of nanoscale AB rings with an embedded scattering center in one arm and a magnetic flux passing through its center. In the AB ring with double coupled-quantum dots (QDs), we show that the overlapping of Fano resonances arises from the strong interaction between two quasi-bound levels in the coupled QDs, and that the zero of the Fano resonance is shifted to the complex plane. In addition, we also study the effects of an asymmetry in the arm by inserting an attractive potential well (dot) in one arm. The combined transmission resonance effects as functions of variables of the ring structure and the potential are presented. It is shown that an attractive potential in one of the arms in the AB ring generates an asymmetric Fano resonance in the transmission.     

Eigenstate Selection in Open Quantum Dot Systems: On the True Nature of Level Broadening

We show that transport in open quantum dots can be mediated by single eigenstates, even when the leads allow several propagating modes. The broadening of these states, generally localized in the interior, can be virtually independent of lead width. As such, the Thouless argument, invoked to suggest that all states should be unresolvable under these conditions, can in fact fail. Thus, any transport theory based on such assumptions (in particular, random matrix theory) must be called into question, as the fluctuations produced by these states can in fact dominate the conductance. These trapped states also produce interesting and potentially useful effects in coupled dot systems as well.     

Simulation of Spin-Qubit Quantum Dot Circuit with Integrated Quantum Point Contact Read-Out

We provide a physical analysis of the charging and detection of the first few electrons in a laterally-coupled GaAs/AlGaAs quantum dot (LCQD) circuit with integrated quantum point contact (QPC) read-out. Our analysis is based on the numerical solution of the Kohn-Sham equation incorporated into a three-dimensional self-consistent scheme for simulating the quantum device. Electronic states and eigenenergy spectra reflecting the particular LCQD confinement shape are obtained as a function of external gate voltages. We also derive the stability diagram for the first few electrons in the device, and obtain excellent agreement with experimental data.     

量子计算机

量子力学和计算机理论,这两个看起来互不相关的领域,其结合却产生了一门富于成效的学科:量子计算机。介绍了量子计算机的基本概念和历史背景,分析了相对于经典计算机的优越性、构造和实验方案,以及实现量子计算的困难及其克服途径,展望了量子计算机的发展前景。     

HDDR各向异性NdFeB粘结磁体研究

开发了用ＨＤＤＲ各向异性ＮｄＦｅＢ粉加环氧树脂做的高能积模压成型粘结磁体微波研究了Ｃｏ、Ｇａ含量地ＮｄＦｅＢ粘结磁体的磁性能的影响和工艺重复性,最后做出的各向异性粘结ＮｄＦｅＢＣｏＧａ磁体的磁性能为：Ｂｒ≥８００ｍＴ,ＨＣＪ≥８００ｋｍ,ＡＣＢ≥４４０ｋＡ／ｍ,（ＢＨ）ｍａｘ＝１２７±１６ｋＪ／ｍ＾３     

智能化变电站内量子通信纠错编解码的量子逻辑线路

智能化变电站、换流站内复杂多变的电磁环境会使其中的量子通信系统产生量子比特差错问题。为了解决该问题,提出一种量子通信纠错编解码方法,并用量子逻辑给出相应的量子线路实现方式。通过引入8个量子比特的冗余,通过量子逻辑哈达玛(Hadamard)门和异或门及量子逻辑操作X、Z、?Z和ZX,实现了4种不同差错情况的量子比特纠错,从而保证全双工量子通信系统的正常工作。为了实现信息传输时兼顾高效性与安全性,提供一种新的技术体制和技术方案,对未来变电站、换流站的智能化发展提供了一种新的建设思路。     

磁各向异性常数的快速傅立叶变换估算方法与实现

论述了磁各向异性常数的快速傅立叶变换（ＦＦＴ）的估算原理、实现方法以及实现中磁转矩函数周期的识别、样本的取舍、傅氏级数的系数选取等问题。并给出一个实际计算的例子,该方法在应用中比其它方法更简单、更快。     

基于量子神经网络的电力电子电路故障诊断

针对电力电子电路故障诊断时故障模式间存在交叉数据的模式识别问题,在量子计算和人工神经网络结合的基础上,提出了一种基于量子神经网络的故障诊断方法,并以双桥12相脉波整流电路为例进行故障诊断.实验结果表明:量子神经网络有一种固有的模糊性,它能将不确定性数据合理地分配到各故障模式中,从而使网络具有高性能、更好的鲁棒性和省时的特点,且能正确地识别大部分的样本故障模式,成功地完成电力电子电路的故障诊断.     

量子信息学的理论基础与研究进展

量子信息学是物理学与信息学交叉而形成的一门新兴学科。论述了其建立的理论基础——量子态的纠缠现象,介绍了量子计算机、量子密钥、量子隐形传态等相关高新技术,分析了今后的研究方向,以期对该学科有全面的了解。     

SAR图像各向异性扩散滤波算法

为了抑制SAR图像中固有的乘性相干斑噪声,本文提出了一种基于各向异性扩散滤波的新算法。该算法首先将自蛇扩散引入经典的SRAD与DPAD算法各向异性扩散方程中,形成了一种带边缘增强功能的各向异性扩散新方程;然后利用改进Frost滤波系数作为扩散方程的新扩散函数,形成了一种既能有效抑制相干斑,又能较好保护边缘、抑制块效应现象的新扩散函数。实验表明,新扩散滤波算法在相干斑抑制、边缘保护、块效应抑制方面均比传统各向异性扩散滤波算法更优异。     

提高干压各向异性SrM磁体磁性能的方法

以Y30H-1的SrM预烧料为原料,通过对二次添加剂、二次球磨及烧结曲线的调整,做出了Br≥380mT,Hcb≥240kA穖-1,Hcj≥250kA穖-1,(BH)max≥27.0kJm-3的干压各向异性锶铁氧体产品。     

ALA转子电机直接转矩控制研究与仿真

介绍了ALA转子电机的基本原理及其直接转矩控制(DTC)的基本理论.在Simulink环境下,搭建ALA转子电机及其直接转矩控制系统的模型.对ALA转子电机DTC系统起动及负载变化等情况进行了研究.仿真结果表明,直接转矩控制可以克服ALA转子电机开环难以起动的缺点.ALA转子电机的直接转矩控制仿真系统结构简单,实现容易...     

无取向硅钢片各向异性磁致伸缩特性模拟

基于一维磁致伸缩测量装置,提出了单片无取向硅钢片任意方向磁致伸缩特性的测量方法,得到了材料不同磁化方向上磁致伸缩回环,并提取了描述磁致伸缩特性的单值曲线。建立了描述磁致伸缩与磁场关系的?-(?B,Bmax)磁致伸缩数学模型,给出了由测量数据拟合得到的二维磁致伸缩特性曲面。基于Fortran语言编制了耦合上述磁致伸缩模型的有限元计算程序,并分析了一台同步发电机定子铁心的磁致伸缩。研究表明,无取向硅钢片具有任意方向各向异性的磁致伸缩特性,而该文提出的磁致伸缩测试方法和数学模型可以有效地分析硅钢片磁致伸缩各向异性特性。