A computer simulation scheme for various solid-state devices

The main computational scheme for the determination of the device-circuit interaction and the internal dynamics of the solid-state device are described. Certain important details are separately discussed in Appendixes. A unique feature in the simulation is the boundary condition at the electrode, characterized here by an energy barrier. Formulated in this way, successful simulations of the Gunn diode, injection-controlled amplifier, IMPATT diode, TRAPATT condition, controlled-avalanche transit-time (CATT) triode, as well as other phenomena reported in the literature, have been demonstrated.     

Quantum dot-based quantum buses for quantum computer hardware architecture

We propose a quantum bus based on semiconductor self-assembled quantum dots. This allows for transmission of qubits between the different quantum registers, and could be integrated in most of the present proposal for semiconductor quantum dot-based quantum computation.     

Cold atoms in optical lattices as qubits for a quantum computer

An overview is presented of qubit arrays in the form of cold neutral atoms trapped in an optical lattice. The current status and future direction of this qubit realization are discussed. A variant is considered that is based on the dipole-dipole interaction of atoms excited into Rydberg states. The results are presented of the first experiments on the observation of the dipole-dipole interaction between a small number of Rydberg atoms.     

Modeling the solid-state reaction between Sn-Pb solder and a porous substrate coating

Solder joints in hybrid microelectronic circuit electronics are formed between the solder alloy and the noble metal thick film conductor that has been printed and fired onto the ceramic. Although the noble metal conductors provide excellent solderability at the time of manufacture, they are susceptible to solid-state reactions with Sn or other constituents of the solder. The reaction products consist of one or more intermetallic compounds (IMC). The integrity of these solder joints can be jeopardized by formation of IMC layers, which can have thermal and mechanical properties that are substantially different from the solder and substrate and which can consume the conductor layer by solid-state reaction. Analytical models predicting IMC growth for a variety of conditions are needed to improve predictions of long-term joint reliability and manufacturing processes. Unfortunately, because of the inherent porosity of thick film conductors, IMC growth in conductors cannot be well predicted by simply applying growth kinetics to a quasi-one-dimensional layer geometry. Rather, IMC growth involves a complicated geometry in which the interfaces between solid-state phases grow, intersect, and coalesce. In such geometries, explicit boundary tracking, which is normally done in one-dimensional models, is impractical. In heat transfer analyses, an implicit approach, referred to as the enthalpy method, has been used to address multidimensional problems in which interface displacement is controlled by an energy flux. However, an analogous general approach has not been available for mass transfer and reaction analyses. This paper discusses initial 2-D results from a coupled experimental and computational effort to develop a mathematical model and computer code that will ultimately predict 3-D intermetallic growth in porous substrate-solder systems. The numerical model is based on an implicit interface tracking approach developed for diffusion-reaction analyses in complicated geometries. To illustrate the implicit approach with a “real” system, the 2-D calculations were based on the reaction couple formed between 63Sn-37Pb solder and 76Au-21Pt-3Pd substrates. Physical constants in the model were evaluated from experimental data. Consumption of the thick film was predicted as a function of time and compared with data from independent experiments.     

单片机在可调谐固体激光器中的应用

本文阐述了脉冲钛宝石激光系统的光路安置和单片机自动控制的波长调谐系统。本文着重介绍了单片机的控制功能及其硬、软件系统。     

基于经典计算机的量子加密算法仿真

量子密钥分配协议是近几年研究信息安全的一大热点,它的具体实现方法也备受关注．给出了在经典计算机上表示量子态的制备和测量方法,并编制相应的程序,实现了多种量子密钥分配协议仿真．将获得的结果与理论分析结果相比较,两者的一致性表明在现有计算机上仿真量子密钥分配协议是完全可行的,这为量子加密、乃至量子信息处理的研究提供了一种新的手段。     

计算机网络通信的技术特点与发展前景探讨

随着全球信息化、数据化的进程不断加快,人们对于通信的需求已不能停留在传统的通信技术层面上,而是需要更快、更新的通信方式来满足人们逐渐扩大的需要。计算机网络通信的出现,能够更加及时地传递信息,恰恰满足了人们在新时代背景下的通信畅想。现阶段,计算机网络通信技术已经普遍运用到了千家万户中。文章对计算机网络通信的技术特点进行分析,并对其发展前景进行探讨。     

激光相干控制与量子计算中的逻辑门

利用激光控制分子内不同振动模态之间能量转移的几率，论证了激光相干控制能够完成某种量子逻辑门（如量子Ｆｒｅｄｋｉｎ门）的功能。     

Element base of quantum informatics I. Qubits of a quantum computer based on single atoms in optical traps

A brief overview of the current state of the experimental research on the development of the element base of quantum computers with qubits based on single neutral atoms trapped in optical traps. The requirements for qubits, peculiarities of single neutral atoms as qubits, methods for the quantum register development and for the implementation of single-qubit quantum logic operations in the laser and microwave fields, and two-qubit operations through the dipole–dipole interaction after a short laser excitation of atoms to the Rydberg states are discussed. The results of the experiments on the observation of the interaction of two Rydberg atoms at a Förster resonance controlled by the dc and radio-frequency electric field are presented.     

Modeling and computer simulation of wave propagation in linealline-of-sight microcells

The model and implementation principles governing the computer simulation of line-of-sight (LOS) microcell wave propagation are presented. Multiray propagation above a plane earth constitutes the basic model. For rural microcells, two rays are used while, for urban microcells, 10 rays are used propagating in a dielectric canyon. The model is applied to two relevant problems. In the first, control of electric field falloff with distance, r, is studied. ln the second, the advantages of switched transversal antenna diversity are demonstrated. Power falloff rates of 1/r⁴ and 1/r⁶ were obtained for simple two-element array structures. This may provide an additional interference control tool in the layout and design of microcells. The interference between the various rays propagating in lineal urban microcells results in deep nulls at various locations. The deleterious effects of these nulls can be eliminated by employing simple switched transverse antenna diversity     

The hyperfine energy spectrum of31P donors in a silicon NMR quantum computer

The effect of an electric field on the hyperfine interaction constant (HIC) of a donor atom is considered within the silicon quantum computer model. The field is produced by the potential of a circular (disk-shaped) or strip gate. A spread in the HIC values because of inaccurately placing donor atoms under the gate is estimated. The energy spectrum of the electron-nuclear spin system for two interacting donor atoms with different HICs is evaluated. Two pairs of levels anticrossing in the ground state are shown to exist.     

The p-n junction quantum well APD: A new solid-state photodetector for lightwave communications systems and on-chip detector applications

A novel variation on the doped quantum well avalanche photodiode is presented that provides comparable signal-to-noise performance at more realizable material doping requirements. The device consists of repeated unit cells formed from a p-n Al0.48In0.52As junction immediately followed by near-intrinsic Ga0.47In0.53As and Al0.48In0.52As layers. As in the doped quantum well device, the asymmetric unit cell selectively heats the electron distribution much more than the hole distribution prior to injection into the narrow-gap Ga0.47In0.53As layer in which impact ionization readily occurs. The effects of various device parameters, such as the junction doping, Ga0.47In0.53As and intrinsic Al0.48In0.52As layer widths as well as the overall bias on the electron and hole ionization rates, is analyzed using an ensemble Monte Carlo method. From the determination of the ionization rates and the ionization probabilities per stage, P and Q, an optimal device design can be obtained that provides high gain at low multiplication noise. In addition, a structure that operates at less than 5 V bias is presented that can provide moderate gain at very low noise. It is expected that the device designs presented herein can serve either as high-gain low-noise detectors for lightwave communications systems or as moderate-gain low-noise detectors for on-chip application.