量子计算的研究与应用

对量子计算的最新研究方向进行了介绍,简述了量子计算和量子信息技术的重要应用领域。分析了量子计算机与经典计算机相比所具有的优点和目前制约量子计算机应用发展的主要因素,最后展望了其未来发展趋势。     

An Explicit Universal Gate-Set for Exchange-Only Quantum Computation

A single physical interaction might not be universal for quantum computation in general. It has been shown, however, that in some cases it can achieve universal quantum computation over a subspace. For example, by encoding logical qubits into arrays of multiple physical qubits, a single isotropic or anisotropic exchange interaction can generate a universal logical gate-set. Recently, encoded universality for the exchange interaction was explicitly demonstrated on three-qubit arrays, the smallest nontrivial encoding. We now present the exact specification of a discrete universal logical gate-set on four-qubit arrays. We show how to implement the single qubit operations exactly with at most 3 nearest neighbor exchange operations and how to generate the encoded controlled-NOT with 27 parallel nearest neighbor exchange interactions or 50 serial gates, obtained from extensive numerical optimization using genetic algorithms and Nelder–Mead searches. We also give gate-switching times for the three-qubit encoding to much higher accuracy than previously and provide the full speci.cation for exact CNOT for this encoding. Our gate-sequences are immediately applicable to implementations of quantum circuits with the exchange interaction. PACS: 03.67.Lx, 03.65.Ta, 03.65.Fd, 89.70.+c     

量子计算与量子密码的原理及研究进展综述

量子计算与量子密码是基于量子效应的计算技术和密码技术.1984年Bennett和Brassard提出了第一个量子密钥分发协议,开启了量子密码学的研究,此后相继在量子加密、量子签名等领域进行了大量研究.1994年,Shor利用量子Fourier变换,设计了第一个实用的量子算法,在多项式时间内对大整数进行因子分解.1996年,Grover提出了量子搜索算法,能够对无结构数据进行二次加速.Shor算法和Grover算法的提出不仅体现了量子计算的优越性,还对传统基于数学困难问题的密码学体制造成威胁.经过半个世纪的发展,量子计算与量子密码在理论与实践的研究上都取得了丰硕的成果.从量子力学的数学框架、基本概念和原理、量子计算基本思想、量子密码研究进展及主要思想等方面进行总结梳理.     

量子算法与量子衍生算法

随着经典计算发展日趋缓慢,量子计算正逐渐成为研究领域的关注热点.该文简要介绍了量子计算的基本原理.接着,从当前量子计算领域中的两个活跃研究方向——量子算法和量子衍生技术研究出发对整个量子算法领域主要发展脉络进行梳理并总结目前量子计算研究的发展规律.最后,该文针对这两个方向提出了若干量子计算领域的发展趋势.通过对量子计算研究领域的综述和展望,对后续量子计算研究发展具有一定的指导意义.     

量子计算及量子算法研究进展

量子相干性和量子纠缠等特性为量子计算带来了完全不同于经典计算的独特运算方式,量子计算表现出的并行性更是令经典运算望尘莫及。Shor算法的提出完全展示了量子算法在解决某些经典问题时的优势,接踵而至的Grover搜索算法进一步诠释了量子计算的威力。此后,算法“量子化”在国际上掀起了研究的热潮,尤其在量子智能算法方面取得了不错的成果。文章首先介绍量子计算的发展现状和基本原理;然后列举三种典型的量子算法,展示量子计算的优越性;最后介绍该领域的研究进展。     

Quantum Computation Violates Mirror Symmetry

The CNOT gate is asymmetric with respect to parity. It requires interaction with the environment, and cannot be realized as an isolated quantum collision.     

一种改进的量子遗传算法及其应用

针对基于Bloch球面坐标编码的量子遗传算法应用中的优化效率低和局部寻优较差能力问题,提出2点改进措施：在比较种群的基础上将局部搜索与全局搜索相结合;依据三链特性将搜索空间扩展为3Bloch球面空间。将改进算法应用于多变量函数极值优化问题,仿真结果表明,该改进算法寻优代数小、收敛速度快、效率高,并且具有较好的种群多样性,验证了改进措施的有效性。     

Fiber Optics Protocols for Quantum Communication

We show how the techniques developed for long distance quantum key distribution in optical fibers can be used to demonstrate other quantum information processing and communication protocols. We present a fiber optics realization of the Deutsch–Jozsa and Bernstein–Vazirani algorithms. We describe a method, called “error filtration”, for reducing errors in quantum communication channels, and present an experimental implementation thereof. We discuss the cryptographic primitive of string flipping, and present an experimental implementation which has higher security than achievable using any classical protocol.     

Quantum Computation with Abelian Anyons

A universal quantum computer can be constructed using abelian anyons. Two qubit quantum logic gates such as controlled-NOT operations are performed using topological effects. Single-anyon operations such as hopping from site to site on a lattice suffice to perform all quantum logic operations. Anyonic quantum computation might be realized using quasiparticles of the fractional quantum Hall effect. PACS: 03.65-Lx     

量子纠缠和量子计算

量子纠缠是量子力学中的一种非经典现象。本文从介绍纠缠和纠缠态出发,着重讨论纠缠的本质和非定域性概念。文末还讨论了纠缠在量子计算中的作用：它是量子计算优于经典计算的重要原因之一。     

Universal and General Quantum Simultaneous Secret Distribution with Dense Coding by Using One-Dimensional High-Level Cluster States

A universal and general quantum simultaneous secret distribution(QSSD)protocol is put forward based on the properties of the one-dimensional high-level cluster states,in which one sender dispatches different high-level classical secret messages to many users at the same time.Due to the idea of quantum dense coding,the sender can send different two-dit classical messages(two d-level classical numbers)to different receivers simultaneously by using a one-dimensional d-level cluster state,which means that the information capacity is up to the maximal.To estimate the security of quantum channels,a new eavesdropping check strategy is put forward.Meanwhile,a new attack model,the general individual attack is proposed and analyzed.It is shown that the new eavesdropping check strategy can effectively prevent the traditional attacks including the general individual attack.In addition,multiparty quantum secret report(MQSR,the same as quantum simultaneous secret submission(QSSS))in which different users submit their different messages to one user simultaneously can be gotten if the QSSD protocol is changed a little.     

量子测量与量子计算

本文的讨论主要集中在量子力学中测量部分,首先从量子力学的几大公设出发,着重分析测量公设的含义。然后提出量子力学争论的焦点问题之一——测量问题,并通过分别阐述塌缩原理、非塌缩原理以及对二者的比较来分析各种说法的合理性。接下来简要讨论同时测量问题。最后简略描述测量在不同量子计算模型中的体现,并对测量带来的问题做了思考。     

量子Daubechies-D（4）小波变换算法及应用研究

由于量子计算相比经典计算具有突出的优越性,设计基于通用量子语言Q_language的量子Daubechies-D（4）小波变换算法对于小波变换的应用和量子算法的完善具有重要的意义。文章分析了Daubechies-D（4）小波变换过程,给出了量子Daubechies-D（4）小波变换算法的Q_language语言描述,并分析得出其时间和空间复杂度,给出了实现量子Daubechies-D（4）小波变换应用方法。     

开放环境下多比特量子计算机的相干控制模型

研究了开放环境下多比特量子计算系统的相干控制建模问题.基于开放量子系统的数学模型,选取适当的矩阵基将描述多比特量子计算机的复矩阵动态控制模型转化为实向量空间上的控制模型,并给出计算相应的结构系数的方法.这些工作提供了进一步研究控制律设计的基础.     

Quantum Computing with Trapped Ion Hyperfine Qubits

We discuss the basic aspects of quantum information processing with trapped ions, including the principles of ion trapping, preparation and detection of hyperfine qubits, single-qubit operations and multi-qubit entanglement protocols. Recent experimental advances and future research directions are outlined. PACS: 03.67.Lx, 32.80.Pj, 32.80.Qk, 42.50.Vk     

Experimental Concatenation of Quantum Error Correction with Decoupling

We experimentally explore the reduction of decoherence via concatenating quantum error correction (QEC) with decoupling in liquid-state NMR quantum information processing. Decoupling provides an efficient means of suppressing decoherence from noise sources with long correlation times, and then QEC can be used more profitably for the remaining noise sources. PACS: 03.67.Lx, 03.65.Bz     

绝热量子搜索算法中的纠缠与能量分析

为了进一步研究量子纠缠与量子计算速度及能量的关系,通过计算von Neumann纠缠熵,分析了时间复杂度分别为O(N )和O(1)的绝热量子搜索算法的量子纠缠度随时间的变化关系,并对两者进行了比较.实验结果表明,量子纠缠对绝热量子计算的运行时间具有明显的影响,较大的纠缠可以导致更短的运行时间,反之亦然.同时对纠缠与能量的关系给出了一般性解释,即注入能量导致系统的纠缠增大,并因此缩短算法的运行时间.此外还分析了纠缠与量子系统初态的关系.实验表明系统初态形式不同,其纠缠度也不一样.初态为等幅叠加态的算法涉及的纠缠度明显大于初态为非等幅叠加态的算法.     

基于量子遗传算法的盲源分离算法研究

在改进遗传量子算法的基础上，提出了一种新的量子遗传算法并从理论上证明了算法的全局收剑性．提出了基于量子遗传算法与独立分量分析算法相结合的盲源分离新算法．仿真结果表明：新方法比采用常规遗传算法的盲源分离方法具有明显的高效性．     

量子遗传算法及其在图像盲分离中的应用研究

在改进Han的遗传量子算法的基础上，提出一种新的量子遗传算法．算法中采用多量子比特来编码多状态基因，构造了各个体之间的联合量子交叉，提出了通用的量子旋转门演化策略和动态调整旋转角机制．将量子遗传算法与独立分量分析算法相结合，提出一种图像信号的盲分离方法．仿真结果表明了该算法的有效性．