基于二维囚禁离子实现受控非门、交换门和相位门

研究了二维囚禁离子与光场相互作用系统中几种基本量子逻辑门的实现方案.通过适当选取激光场与离子内部跃迁频率的失谐量,简化了系统的哈密顿量,并进一步推导出受控非门(C-NOT门)、交换门与相位门的实现方法.在此过程中,系统需满足Lamb-Dicke极限,并要求光场的Rabi振荡频率远远小于离子的振动频率. 关键词： 囚禁离子 受控非门(C-NOT门) 交换门 相位门     

单离子阱中基本量子逻辑单元的实现

建议了一种利用单个囚禁冷却离子实现基本量子逻辑门操作(单比特门和两比特受控旋转门)的理论方法,通过数值计算给出了各种相关实验参量的合理设置要求.在这一方案中,量子逻辑门的操作既不要求离子辅助能级的参与,也不限定只在弱耦合的LambDicke区内进行,因而将更容易地为实验所实现 关键词： 量子计算机 受控量子逻辑门操作 LambDicke耦合参数     

离子阱中以声子为媒介的多体量子纠缠与逻辑门

高保真度的多离子纠缠和量子逻辑门是离子阱量子计算的基础.在现有的方案中, M?lmer-S?rensen门是比较成熟的实现多离子纠缠和量子逻辑门的实验方案.近年来,还出现了通过设计超快激光脉冲序列,在Lamb-Dicke区域以外实现超快量子纠缠和量子逻辑门的方案.这些方案均借助离子链这一多体量子系统的声子能级来耦合离子之间的自旋状态,并且均通过调制激光脉冲或设计合适的脉冲序列解耦多运动模式,来提高纠缠门的保真度.本文从理论和实验层面分析了这些多体量子纠缠和量子逻辑门操作的关键技术,揭示了离子阱中利用激光场驱动离子链运动态,通过非平衡过程中的非线性相互作用,来实现量子逻辑门的基本物理过程.     

基于频率调制激光驱动的囚禁离子几何相位逻辑门

为了避免激光相位的起伏对几何相位逻辑门保真度的影响, 提出一种基于囚禁离子的量子几何相位逻辑门的新方案。该机制是利用一束频率调制的行波激光场作用于两个囚禁离子上实现的。它的优点有：操作简单,仅需一步就能实现。不灵敏于激光场的相位也不需要对囚禁离子进行个别寻址。     

离子阱中量子逻辑门的实现

在实际建造量子计算机时,需要寻找合适的量子系统,实现量子逻辑门,并同时要克服消相干问题.人们提出了许多物理系统,比如:腔QED模型、囚禁离子系统、核磁共振系统、量子点等等.     

囚禁离子非线性Jaynes-Cummings模型量子场熵演化特性

利用VonNeuuman量子约化熵理论研究了驻波激光场与囚禁在谐振势中的离子单量子共振相互作用系统中量子场熵的时间演化特性,通过数值计算详细讨论了Lamb-Dick参数、离子质心在驻波激光场中的位置以及囚禁离子初始状态对量子场熵演化特性的影响.结果表明:Lamb-Dick参数影响囚禁离子与驻波激光场之间量子纠缠的频率和幅度,其值越大离子与光场之间的平均纠缠程度越低;随着离子质心从驻波激光场的波节向波腹移动,二者之间量子纠缠的振荡频率逐渐变慢,纠缠强度逐渐减弱;随着囚禁离子处于激发态概率的减小,离子与光场之间的量子纠缠呈现先增强后减弱的变化趋势.这些特性对于纠缠态的制备以及利用囚禁离子进行量子通讯等信息处理过程有一定的参考价值.     

几率量子隐形传态的离子阱方案

本文提出了一个在分别囚禁于不同离子阱中的两个离子间实现几率量子隐形传态的简单方案,Alice对离子1和离子2的内态进行联合测量并通过经典通道告诉Bob测量结果,Bob利用一束经典驻波场激光与离子3相互作用并控制相互作用的时间就能够在离子3上最佳几率地重现离子1的初始内态.     

相干时间超过10 min的单离子量子比特

能够长时间储存量子信息的量子存储设备是实现大规模量子计算和量子通信的基本要素.与其他量子计算平台相比,囚禁离子系统的优势之一在于具有很长的相干时间.此前,基于囚禁离子的单量子比特相干时间不到1 min.研究发现,在囚禁离子系统中,限制量子比特相干时间的主要因素是运动能级加热和环境噪声,其中后者包含环境磁场涨落和微波相位噪声.在同时囚禁171Yb+离子和138Ba+离子的混合囚禁系统中,通过实施协同冷却和动力学解耦,可以实现相干时间超过10 min的单离子量子比特.这一技术有望用于实现量子密码学和搭建混合量子计算平台.     

基于频率调制激光驱动的囚禁离子几何相位逻辑门

为了避免激光相位的起伏对几何相位逻辑门保真度的影响,提出一种基于囚禁离子的量子几何相位逻辑门的新方案.该方案是利用一束频率调制的行波激光场作用于两个囚禁离子上实现的.它的优点有:操作简单,仅需一步就能实现,不灵敏于激光场的相位也不需要对囚禁离子进行个别寻址.     

Paul阱中两个超冷离子的量子统计特性

讨论两个囚禁在Ｐａｕｌ阱的对称轴上的超冷离子的量子统计特性，可以发现，它们的稳定囚禁不仅与阱的稳定区有关，而且与它们自身的自旋和电荷数大小有关。     

用于聚焦离子束系统的离子源

介绍了现阶段两种用于聚焦离子束系统的离子源——液态金属离子源和气体场发射离子源的基本原理, 并对比了它们的优缺点。由于目前这两种离子源都难以满足纳米加工领域不断提高的技术要求, 因此提出了一种用于聚焦离子束的新型离子源——电子束离子源, 并介绍了电子束离子源的基本原理, 给出了设计参数、 模拟结果（20 kV的Ar+离子束, 发射度约为5.8×10-5·mm·mrad, 束斑约为1 μm）和初步的实验结果。 There are two kinds of ion sources, Liquid Metal Ion Source and Gas Field Ion Source, used to provide ion beams for the Focus Ion Beam system. The working mechanism of the two kinds of sources is presented and their advantages and disadvantages are summarized. With the rapid development in the nano technology, the requirements are hardly met with these two kinds of ion sources. Therefore, a new kind of ion source, electron beam ion source, is developed for the Focus Ion Beam system. The basic principle of the electron beam ion source is introduced and the design parameters, the result of the simulation (20 kV Ar+, extracted emittance is 5.8×10-5π·mm·mrad, raduis of the ion beam about 1 μm.) and the primary experimental results are presented     

Ion Beam Driven Ion Cyclotron Double Layers

We present here a self consistent theory of small amplitude double layers associated with electrostatic ion cyclotron waves in a plasma containing hot electrons, cold ions and traversed by an ion beam. It has been shown that compressive type of double layers solution exists when θ_b (beam temperature) < α_b (beam concentration) < 1.     

On the Cost of Ion Production in Radio-Frequency Ion Thrusters and Technological Ion Sources

The power balance in the inductive discharge of a radio-frequency ion source is worked out by calculating the power losses caused by plasma deposition on the surfaces bordering it, by the power consumed for positive-ion generation and pre-acceleration, by eddy currents, and by propellant-atom excitation. The relationship between the minimal consumption of high-frequency power per unit of ion current of the thruster and electron temperature and geometric parameters of the gas-discharge chamber is presented.     

Energetic Ion Effects on the Ion Saturation Current

The ion saturation current is very important in probe theory, which can be used to measure the electron temperature and the floating potential. In this work, the effects of energetic ions on the ion saturation current are studied via particle-in-cell simulations. It is found that the energetic ions and background ions can be treated separately as different species, and they satisfy their individual Bohm criterion at the sheath edge. It is shown that the energetic ions can significantly affect the ion saturation current if their concentration is greater than T_e/(γi2 T_(i2))~(1/2), where Te is the electron temperature, and γ_(i2) and T_(i2) represent the polytropic coefficient and temperature of energetic ions, respectively. As a result, the floating potential and the I V characteristic profile are strongly influenced by the energetic ions. When the energetic ion current dominates the ion saturation current, an analysis of the ion saturation current will yield the energetic ion temperature rather than the electron temperature.     

Ion implantation

Some developments in applications of Mössbauer spectroscopy to investigate ion-implanted radioactive source isotopes in solids are presented. Emphasis is layed on impurity and defect studies in metals and semiconductors. The particular role of Mössbauer spectroscopy in comparison to and in combination with other analytical techniques is illustrated. Recently developed on-line implantation techniques are described, their merits and prospects are discussed.     

Ion implantation

The extreme sensitivity of Mössbauer Spectroscopy to the local atomic and electronic configuration around ion implanted Mössbauer probes is demonstrated in a number of recent defect configuration studies in semiconductors and metals. A surge of interest is observed towards Mössbauer studies on high dose implantations connected with materials research: recent studies are reviewed dealing with ion beam synthesis, ion beam modification and ion beam mixing of materials.     

平面刻槽离子阱的热噪声引起的离子加热研究

研究了和平面刻槽离子阱中的电压热涨落噪声引起的离子加热和离子加热的直接计算模型,给出了离子加热的加热尺度,并利用有限元分析方法计算了当刻槽宽度和射频电极宽度比例α发生变化时加热尺度的变化。同时,还利用涨落耗散原理计算了控制电极的阻抗热涨落对离子产生的加热效应,并给出了x和y方向电场涨落的谱密度表达式,通过计算给出了较好的α值。     

A Simple Ion Source for Monoenergetic Multiply Charged Ion Beams

A small and inexpensive electron beam ion source for multiply charged ions of noble gases is described. One of its essential characteristics is the low energy spread of the extracted ion beam, which depends on the charge state q of the ions and amounts to ∽q × 50 meV. The total ion current containing ionic states up to q = 6 is in the order of 10 nA. The design, construction and important parameters of the ion source are described.