Superconducting cavities and charge qubits: Spectroscopy and quantum operations. Part II

In the second part of our review, we focus on such urgent problems of modern physics as the use of superconductors in quantum informatics and coherent control of the state of mesoscopic systems.     

Quantum error correction in silicon charge qubits

The interaction of the quantum register with a noisy environment that leads to phase and bit errors is considered. Modeling of 5-qubit and 9-qubit error-correction algorithms for various environments is performed. It is shown that the use of the quantum correction leads to a quadratic decrease in the error probability. The efficiency of applying the 5-qubit algorithm of error correction for a silicon double-dot qubit is shown.     

Quantum teleportation with qubits

An overview of experiments on quantum teleportation with qubits is presented. Issues are analyzed concerning Bell-state measurement and entangled-state preparation. Unitary transformations are discussed that are required in the teleportation of an unknown or a known state.     

Electronic characteristics of the singly ionized pair of phosphorus donors in silicon and operations with charge qubits

The electron energy spectrum of the singly ionized pair of phosphorus donors in silicon, P ₂ ⁺ , is calculated numerically, taking into account the sixfold degeneracy of the conduction band. The envelopes of wave functions of different states are determined. The results are used to simulate operations with the P ₂ ⁺ /Si-based charge qubits via exposure to laser pulses.     

Superconducting resonators and charge qubits: Spectroscopy and quantum operations. Part I

For the past few years, considerable progress has been made in the fabrication of quantum devices using mesoscopic semiconductor elements. These devices can represent the elemental base for a wide class of high-tech devices from supersensitive detectors of an electromagnetic field to reliable sources of single photons and quantum computers. The article reviews the main experimental results obtained to date with the participation of superconducting quantum devices.     

Quantum noise and the quality control of hardware components of quantum computers based on superconducting phase qubits

A general approach to the provision of the quality and efficiency of quantum information technologies is proposed. The approach is based on the analysis of quantum noise generated on the implementation of quantum operations. The method of precision quantum measurements of logic quantum gates based on superconducting phase qubits is developed. The universal method of quantum state and process tomography is used to carry out a comprehensive analysis of the fidelity of the tomography of two-qubit SQiSW, CNOT, and CZ gates arising from the capacitive coupling between qubits. The method of optimization of quantum process tomography is proposed to provide a substantially higher degree of adequacy and fidelity compared to those attained by previously known methods. The examples of simulation of depolarizing quantum noise and amplitude- and phase-relaxation processes on the implementation of quantum operations in registers are considered.     

Quantum confinement and charge control in deep mesa etched quantumwire devices

Novel aspects of charge confinement in quantum wires are investigated with a self-consistent Schrodinger-Poisson model in the high-temperature regime. A decreasing eigenenergy separation with gate bias is revealed which differs from the behavior observed in 2-D devices. In addition, charge control is examined and an analytical approximation relating charge density to gate bias is obtained     

用单一表达式研究由两腔组成的半导体激光器

用射线法导出两段式半导体激光器的端面输出谱。该结果既适用于两段式双稳激光器，也适用于简单的外腔式激光器，于是，我们首次用一个统一的式子对这两种看起来颇为不同的器件的某些特性进行了研究。     

Scheduling semiconductor device test operations on multiheadtesters

Past attempts to devise scheduling methods for the device test operations of semiconductor manufacturing firms fail to address a significant characteristic of multiple-head test systems-the dependency of processing rates on the lots processed simultaneously on the testers. Since the problem has never been modeled accurately in the scheduling literature, feasibility and performance of previously proposed scheduling methodologies for multihead testers may not be accurately assessed. In this paper, we describe the multihead tester scheduling problem, present an enumeration solution procedure, and illustrate the problems of previously suggested tester scheduling algorithms     

电场力显微镜不同探针对表面电荷注入的影响

在电场力显微镜(EFM)下利用不同金属镀层微探针,在微纳米尺度下对聚酰亚胺薄膜的表面电荷生成特性进行研究。采用电场力显微镜导电探针在聚酰亚胺薄膜表面注入电荷,并对微纳米区域产生的电荷进行表征,结果表明不同金属镀层的微探针对聚酰亚胺薄膜上电荷注入效果不同。铂铱合金镀层具有比钴铬合金镀层更高的功函数fm,因此前者在金属-电介质接触中产生更大肖特基势垒,进而降低了电荷的注入程度。该研究为微纳米尺度下探索聚合物绝缘材料表面电荷生成、发展机理提供了一个新的研究方法和途径。     

Conductance of quasi-two-dimensional semiconductor systems with electrostatic disorder in the region of the percolation metal-insulator transition

Special features of the percolation transition in quasi-two-dimensional (quasi-2D) electron systems (metal-nitride-oxide-semiconductor structures with n-type inversion channels) with a strong fluctuation potential (FP) and a gate length smaller than the correlation radius of a percolation cluster (in which case the structure conductance is controlled by isolated saddle-point regions of the FP) are considered. Experimentally measured dependences of the conductance on the field-electrode potential and the temperature are analyzed in the context of the Landauer-Büttiker formalism. Energy parameters of the FP saddle-point regions and effective density of electron states (N _SS ∝ m/π?²) near the percolation level are determined from the experimental data. Consistency between the experimental results and the proposed statistical model of the formation of FP saddle-point regions in quasi-2D systems is demonstrated. It is shown that saddles transform into potential troughs extended in the direction of the percolation route as the percolation trough is approached.     

Temperature delocalization of charge carriers in semiconductor lasers

The temperature dependences of emission characteristics are investigated for laser diodes based on asymmetric separate-confinement heterostructures with a broadened waveguide. It is established that an increase in the charge-carrier concentration in the waveguide layer is the basic mechanism of saturation in the light-current characteristic with increasing temperature in the CW mode. It is experimentally shown that the temperature delocalization of charge carriers leads to increasing internal optical losses and decreasing external differential quantum efficiency. It is shown that the degree of delocalization of charge carriers depends on the charge-carrier temperature distribution, the threshold concentration, and the quantum-well depth. The effect of thickness and energy depth of the quantum well on the temperature sensitivity of the threshold current and output optical power is considered.     

Distribution of charge carriers in dissipative semiconductor structures

It was experimentally shown that redistribution of the charge-carrier concentration occurred in nonequilibrium electron-hole plasma during formation and excitation of the dissipative structure by a strong electric field in the bulk of Te and InSb single crystals. In this case, if there are only longitudinal autosolitons in the dissipative structure, the carrier concentration decreases outside the autosolitons. The charge-carrier concentration increases outside autosolitons if the transverse autosolitons are present. It is suggested that the longitudinal autosolitons formed in the nonequilibrium electron-hole plasma developed by the Joule heating are “cold” and the transverse autosolitons are “hot”.     

Modelling of electrostatic gate operations in the Kane solid state quantum computer

The nuclear spin quantum computer proposed by Kane [Nature 393 (1998) 133] exploits as a qubit array ³¹P dopants embedded within a silicon matrix. Single-qubit operations are controlled by the application of electrostatic potentials via a set of metallic ‘A’ gates, situated above the donors, on the silicon surface, that tune the resonance frequency of individual nuclear spins, and a globally applied RF magnetic field that flips spins at resonance. Coupling between qubits is controlled by the application of potentials via a set of ‘J’ gates, between the donors, that induce an electron-mediated coupling between nuclear spins. We report the results of the study of the electric field and potential profiles arising within the Kane device from typical gate operations. The extent to which a single nuclear spin can be tuned independently of its neighbours, by operation of an associated A-gate, is examined and key design parameters in the Kane architecture are addressed. Implications for current fabrication strategies involving the implantation of ³¹P atoms are discussed. Solution of the Poisson equation has been carried out by simulation using a TCAD modelling package (Integrated Systems Engineering AG).     

关于如何规避PCB测试点对半导体器件静电损伤的隐患

本文主要对控制器在静电损伤故障中,关于设计方面,如何规避静电损伤问题,从PCB的特殊部位入手,通过设计上的改进,规避控制器因半导体器件的布局不合理,进而导致主板半导体失效的问题.从PCB设计着手,通过结合生产流程、安装流程、设备工装等影响因素,从实际出发,大幅减少控制器制造过程中的ESD和EOS问题.     

Quantum dots: Paradigm changes in semiconductor physics

Deposition of one or a few monolayers of a semiconductor having a lattice constant largely different from the underlying substrate leads to formation of coherent “quantum dot arrays” of densities beyond 10¹¹ cm⁻² in a matter of seconds. Self-organization effects govern their massively parallel formation. Fundamental paradigms of semiconductor physics must be changed in describing such quantum dots or their ensembles. Fiz. Tekh. Poluprovodn. 33, 1044–1048 (September 1999) This article was published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.     

负频反馈半导体激光器的量子噪声

相干光通信系统和相干光学测量对LD的噪声特性要求十分严格,因此LD的噪声及其抑制一直是近年来人们十分关注的问题.为了抑制LD的量子噪声,已采用了几种方法,但这又带来了机械稳定性的问题.最近报道了用NFFB抑制LD的线宽和FM噪声,对此也已有了理论解释但是在的分析中未引入反馈项,相当于开环的情况;的分析中则将反馈项引到了相位方程中,这是不符合客观情况的.本文给出的模型不仅解释了FM噪声的抑制,而且也解释了AM噪声的增大.得到的线宽与实验     

Quantum calculations on quantum dots in semiconductor microcavities. Part II

In this work we continue considering solid hybrid systems formed from semiconductor quantum dots and microcavities integrated into a single optical scheme. In the second part, the main emphasis is on the methods of investigation and on the schemes for recording of the spectra and the time dependences of the population energy level, which illustrate the modern control level of the quantum state of these systems.     

Perfectly and imperfectly controlled quantum operations on a charge qubit

A theoretical investigation is presented into the coherent dynamics of a charge qubit in the form of two tunnel-coupled quantum dots containing a single electron, with the logic states represented by electron orbitals localized at the quantum dots. Analytical expressions are derived for the evolution of a one-or two-qubit system in an applied field. The system and field parameters are evaluated in terms of performing basic one-qubit operations. The possibility is explored for implementing the CNOT operation in a two-qubit system driven by error-free or error-prone control pulses.