超欧姆型热库环境下互感效应对磁通量子比特退相干的影响

在二能级近似下运用Bloch-Redfield方程,研究了超导量子电路中的磁通量子比特退相干在超欧姆热库环境下受互感效应的影响。研究结果表明：（1）在超欧姆热库环境下,提高环境指标系数有利于延长超导磁通量子比特的退相干时间;（2）构建超欧姆型热库环境可以改进固态量子比特的退相干;（3）电感元件间的互感耦合对量子电路系统退相干的影响是比较复杂的,调控好电感元件间的互感耦合有利于提高退相干时间。     

自旋为1/2粒子在消相干量子场作用下的绝热和非绝热几何相位

量子计算来源于量子相干和量子纠缠的特性,但是这两个性质都很脆弱和易于出错,很容易被称为消相干的过程破坏掉,因此如何克服消相干的影响已成为实现量子计算机的一个关键.利用非跃迁轨迹和Berry以及AA几何相位公式,计算了在绝热和非绝热情况下,分别由单模和双模消相干量子场所产生的自旋为1/2系统的几何相位.利用量子跃迁方法,当考虑绝热和非绝热演化时,发现对于非跃迁轨道,其相位修正值是不同的.最后我们从基本原理和量子计算的观点讨论了其结果的意义.     

量子相干与量子消相干

对经典相干和量子相干进行了探讨，介绍量子相干在量子计算和量子信息中的应用。分析几种引起量子消相干的可能原因，并利用Kraus算子和密度矩阵对一种量子消相干模型进行详细地研究。     

量子计算与超导量子计算机

量子计算是一种基于量子力学相干叠加原理的新型计算体系,具有超越传统计算体系的优越性能。超导量子计算因为其在规模可扩展性方面的潜力而得到广泛的重视。超导约瑟夫森结是超导量子计算机方案中的关键器件,可用来控制超导体中的宏观波函数。阐述了量子计算的发展和优势,介绍了约瑟夫森结的原理以及三种超导量子比特的特性,并分析了面临的挑战。     

浅谈超导量子比特封装与互连技术的研究进展

基于超导量子电路的量子计算技术已经在退相干时间、量子态操控和读取、量子比特间可控耦合、中大规模扩展等关键技术上取得大量突破,成为构建通用量子计算机和量子模拟机最有前途的候选技术路线之一。在介绍超导量子比特原理的基础上,结合自主创新成果,对国内外超导量子比特封装与互连技术的发展进行评价,并重点探讨了超导量子比特三维集成封装解决方案以及与外部稀释制冷机测控线路的高密度互连方案,为尽快缩小与国外超导量子计算机的差距提供超导量子比特封装与互连技术支撑。     

三能级原子同时存在辐射和吸收时的量子相干性

量子位和环境的相互作用,将引起量子位能量耗散或相对位相改变,最终导致量子位由相干叠加态退化为混合态或纯态,这种现象被称为量子消相干.针对三能级原子同时存在辐射和吸收时的情况,基于量子力学和Kraus算子理论,利用约化密度矩阵方法,分析了三能级原子密度矩阵元的演化规律,从而研究该系统的量子相干特性.结果表明:初态处于相干叠加态的三能级原子,由于辐射和吸收,可能演化成相干叠加态、未完全混合态、完全混合态、纯态.     

量子信息理论与技术

阐述了量子计算、量子编码、量子通信及量子密码的基本思想与研究新进展,提出了量子信源编码的率失真概念,利用交织器处理量子部分消相干问题的思想及量子多址通信与量子信号阵列处理结合的想法。     

含有超导约瑟夫森结介观互感电路的量子化及其量子效应

给出了含有超导约瑟夫森结的介观互感电路的量子化方案,借助于压缩幺正变换求出了体系的能级以及基态矢量,研究了体系中结端"过剩电荷"(excess charge)与相位差在基态下的量子涨落.结果表明,体系的基态为一旋转的两单模压缩真空态.     

非马尔科夫环境下耦合超导量子比特纠缠态的纠缠消相干

利用共生纠缠度比较详细地研究了一个超导耦合量子比特在非马尔可夫环境下纠缠消相干的演化。研究结果表明：对于不同纠缠初态下的超导耦合量子比特,由于环境作用的记忆反馈效应,处于热平衡环境中的耦合量子比特的纠缠度总是会单调地趋向于零。进一步的研究结果还表明：在非马尔可夫过程中会很快地出现纠缠的突然死亡,耗散越强,纠缠的死亡越快;而在马尔可夫过程中则是缓慢地趋向纠缠的死亡。     

压缩真空场中量子存储单元的消相干特性

两能级原子作为量子存储单元，当存储单元置于压缩真空库（人工制备的库）时，利用存储单元约化密度算符非对角元的时间演化，研究单光子过程和工双光子过程中存储单元的消相干特性。在压缩真空库中，可以消除量子存储单元的消相干。     

基于矩阵初等变换的四量子比特可逆电路综合算法

 量子可逆电路实现信息变换的过程可用一个酉矩阵算子表示,采用酉矩阵表示量子可逆电路能更好地反映量子系统的演化,体现量子计算所特有的属性.本文提出基于矩阵初等变换的4量子比特可逆电路综合算法.该算法恰当地利用量子电路的矩阵表示及变换和邻接矩阵的电路转化规则,总能以较小的量子代价综合出任意给定置换的4量子比特可逆逻辑电路.     

Quantum Computer Simulator Based on the Circuit Model of Quantum Computation

A quantum computer simulator is presented. This simulator is an engineering work and no deep understanding of quantum mechanics is required from the user. The simulator is based on the circuit model of quantum computation in which quantum gates act on quantum registers which comprise a number of quantum bits (qubits). The inputs to the simulator are the initial states of the qubits that form a quantum register and the quantum gates applied at each computation step. The inputs are entered through a graphical user interface. The outputs of the simulator are the matrices that represent the quantum register state at each quantum computation step and graphical outputs that show the probability of measuring each one of the possible quantum register base states and the phase of each state at each computation step. The well-known Deutsch's algorithm and the quantum Fourier transform, which is the base of many quantum algorithms, are presented using this simulator. Furthermore, the generation and variation of entanglement during quantum computations can be calculated using this simulator. The quantum computer simulator is a useful tool for the study of quantum computer circuits, quantum computing, and the development of new quantum algorithms.     

超导电路与体声波谐振器组成的量子iSWAP门方案

高保真度量子门的物理实现是量子计算和量子通信的关键技术之一。根据电路量子声动力学和量子电动力学,提出了由两个具有较长相干时间的超导transmon qubit和一个具有高机械品质因数的薄膜体声波谐振器组成的量子门方案,体声波谐振器起到类似微波光子通道的作用,使两个transmon qubit之间实现量子态交互。该文先用Butterworth van Dyke模型分析体声波谐振器在方案中的等效电路,构建系统的量子化哈密顿量,再用二能级原子 声子混合量子态形式编码系统的量子态,通过调节外磁场来调控系统的输入态,系统的输出态可通过测量模块得到。在Jaynes Cummings模型下,该系统能完成具有高保真度的量子相位交换（iSWAP）门操作。     

基于重叠法的(49,1,9)量子码CNOT门扩展矩形容错构造

CNOT门是量子计算中重要的量子元件,尤其是在量子线路中的容错扩展矩形构造中应用广泛。然而,由于CNOT门扩展矩形容错构造中的容错辅助态的制备线路一般较为复杂,给CNOT门扩展矩形容错构造的设计与实现带来了不便。基于重叠法,提出一种新的(49,1,9)量子纠错码的CNOT门扩展矩形容错构造,并简化了CNOT门扩展矩形容错构造的量子线路。研究结果表明：基于重叠法的CNOT门扩展矩形容错构造中所需要的CNOT门开销比传统的拉丁矩形法制备少224个。     

信息时代的光电子技术

本文从近几年世界范围内掀起的信息化大潮的大背景出发，阐明了光电技术是信息时代的关键技术之一：指出了信息时代的光电子技术发展的重点将主要是超高速光纤传输、光孤子技术、超高速计算、光交换技术和新型量子功能激光器、调制器等；并提出了对策建议。     

Novel design of a fast reversible Wallace sign multiplier circuit in nanotechnology

Today, reversible logic is emerging as an intensely studied research topic, having applications in diverse fields, such as low-power design, optical information processing, and quantum computation. In this paper, we have proposed two reversible Wallace signed multiplier circuits through modified Baugh-Wooley approach, which are much better than the two available counterparts in all the terms. The multiplier is an essential building block for the construction of computational units of quantum computers. Besides, we need signed multiplier circuits for numerous operations. However, only two reversible signed multiplier circuits have been presented so far. In the first proposed architecture, our goals are to decrease the depth of the circuit and to increase the speed of the circuit. In the second proposed circuit, we aimed to improve the quantum cost, garbage outputs, and other parameters. All the proposed circuits are in the nanometric scales and can be used in the design of very complex systems.     

A fuzzy-logic-based approach to accurate modeling of a double gate MOSFET for nanoelectronic circuit design

正The double gate(DG) silicon MOSFET with an extremely short-channel length has the appropriate features to constitute the devices for nanoscale circuit design.To develop a physical model for extremely scaled DG MOSFETs,the drain current in the channel must be accurately determined under the application of drain and gate voltages.However,modeling the transport mechanism forthe nanoscale structures requires the use of overkill methods and models in terms of their complexity and computation time(self-consistent,quantum computations,...). Therefore,new methods and techniques are required to overcome these constraints.In this paper,a new approach based on the fuzzy logic computation is proposed to investigate nanoscale DG MOSFETs.The proposed approach has been implemented in a device simulator to show the impact of the proposed approach on the nanoelectronic circuit design.The approach is general and thus is suitable for any type of nanoscale structure investigation problems in the nanotechnology industry.     

A novel approach in calculating V-I curves of a DC-SQUID coupled toa planar input coil

The influence of a planar input coil on the V-I characteristics of a dc-SQUID (superconducting quantum interference device) has been analyzed by means of computation and experimental investigation. An extended electrical model of the input coil based on transmission lines has been proposed. The frequency behavior of this model has been validated with an expanded copper model. The V-I characteristics of DC-SQUIDs have been calculated with this extended circuit model using a SPICE-type circuit analysis program. The results have been compared with measurements of niobium dc-SQUIDs. In this paper the relationship between the V-I characteristics of the SQUID and the coupling impedance of the washer is demonstrated     

量子通信与量子计算

量子信息学是物理学目前研究的热门领域，它主要包括量子通信和量子计算，文章简要介绍了量子通信和量子计算的理论框架，包括量子纠缠、量子不可克隆定理、量子密钥分配、量子隐形传态、量子并行计算、Shor以及Grover的量子算法，并介绍该领域的研究进展。     

具有低量子代价的快速可逆逻辑综合方法研究

可逆逻辑是最子计算、低功耗设计和纳米技术领域的关键技术。目前可逆逻辑电路的综合方法效率较低、未能达到区域优化,所以,这些方法仪通用于小璎电路的综合。该文提出了一种基于Davio分解式的综合方法,该方法将逻辑函数转换成对应的正Davio决策图,然后通过对每个图节点模版匹配,最终生成可逆逻辑电路。此方法综合速度快,便于优化,适用于大型电路的综合。