量子计算与量子计算机

量子计算的强大运算能力使得量子计算机具有广阔的应用前景。该文简要介绍了量子计算的发展现状和基本原理,列举了典型的量子算法,阐明了量子计算机的优越性,最后预测了量子计算及量子计算机的应用方向。     

量了计算与量子计算机

最子计算的强大运算使得量子计算机具有广泛的应用前景，该文简要介绍了量子计算的发展现状和基本原理，玩举了典型的量子算法，阐明了量子计算机的优越性，最后预测了量子计算及量子计算机的应用方向。     

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。     

量子计算与量子计算机

量子计算是一种依照量子力学理论进行的新型计算,量子计算的基础和原理以及重要量子算法为在计算速度上超越图灵机模型提供了可能。在发展与完善量子计算理论的同时,量子计算机的物理实现方案也被不断提出。光子量子计算机,基于核磁共振、离子阱或谐振子等技术的量子计算机物理模型已被逐一实现。近年来亦出现了几个典型的基于量子计算机的量子算法。2001年在一台基于核磁共振技术的量子计算设备上成功演示的Shor量子算法,显示出量子计算机处理复杂问题的巨大潜能。文章对当前量子计算机物理实现的研究进展进行了综述。     

量子计算

近几年来,量子计算机逐渐引起人们的关注。对于计算机科技人员,量子计算机似乎高深莫测。文章是专门为那些不懂量子力学而又想了解量子计算机的计算机工作者撰写的。介绍了和量子计算有关的术语和符号,并着重阐明一个n位量子寄存器为何能存储2^n个n位数？量子计算机的一次操作为何能计算所有x的f(x)？对于解栽些问题,量子计算机为何能有惊人的运算速度？除了上面3个问题外,还将介绍基本的量子逻辑门和量子逻辑网络,接着介绍一个量子算法,然后介绍量子计算机的组织结构,最后是讨论,将评价量子计算机的优势和弱点,并讨论量子计算机的物理实现和对量子计算的展望。     

量子计算机与经典计算机的比较

本文分析了经典计算机和量子计算机的异同;介绍了量子计算机的原理和特点,指出量子计算和量子信息技术在并行计算、保密通信等方面的重要应用。     

量子计算机来了

量子,一听这个词,你会不会觉得它只属于高端科学,和我们的生活没有什么太紧密的联系?现今,计算机与量子发生了奇妙的"结合",那就是量子计算机。量子计算机(Qantum computer),遵循量子力学的规律,进行高速的数学和逻辑运算,是存储和处理量子信息的装置。如果装置处理和计算的是量子信息,运行的是量子算法,那这个装置就是我们下面要谈的量子计算机。量子计算机     

量子计算与量子计算机展望

量子计算和量子计算机的研究是当代信息科学所面临的一个重大科学课题。阐述了量子计算、量子逻辑门的基本概念和Shor算法,指出了当前实现大规模量子计算所遇到的困难和可能的解决办法。     

量子计算在化学等领域的研究与应用

[目的]近些年来国内外量子计算技术及其应用研究发展迅速,尤其是在量子计算机软硬件系统研发及优越性试验方面取得了积极进展,本文旨在充分展现量子计算技术在材料、化学、生物医药等领域的应用及未来发展前景.[方法]重点围绕变分量子本征求解(VQE)量子算法及量子化学模拟近似计算,对近些年国内外量子计算研究团队在化学、生物及材料...     

量子计算系统软件研究综述

量子计算理论上有望解决诸多经典难解问题, 近年来量子计算机的快速发展正推动这一理论进入实践. 然而, 当前硬件中繁多的错误会造成计算结果出错, 严重限制了量子计算机解决实际问题的能力. 量子计算系统软件位于应用与硬件之间, 充分挖掘系统软件在硬件错误减缓方面的潜力, 对于近期实现有实用价值的量子计算而言至关重要. 由此, 近期涌现了一批量子计算系统软件研究工作. 将这些工作归纳入编译器、运行时系统和调试器3个范畴, 通过对它们的分析总结, 梳理量子计算系统软件的研究现状, 揭示其在硬件错误减缓方面的重要作用. 并对未来的研究方向进行展望.     

量子计算机进入实验阶段

首先简要介绍分层计算的制约;其次介绍最近量子信息的开发,在理论和实践两方面的通信和计算,诸如量子逻辑门、量子密码学、量子交缠性、超距传输的实验性实现、量子算法的首次实验性实现、量子因子分解、量子纪错码以及基于硅片的原子自旋量子计算机;最后讨论克服非相干性困难的方法。     

Service differentiation and fair sharing in distributed quantum computing

In the future, quantum computers will become widespread and a network of quantum repeaters will provide them with end-to-end entanglement of remote quantum bits. As a result, a pervasive quantum computation infrastructure will emerge, which will unlock several novel applications, including distributed quantum computing, that is the pooling of resources on multiple computation nodes to address problem instances that are unattainable by any individual quantum computer. In this paper, we first investigate the issue of service differentiation in this new environment. Then, we define the problem of how to select which computation nodes should participate in each pool, so as to achieve a fair share of the quantum network resources available. The analysis is performed via an open source simulator and the results are fully and readily available.     

Mathematical models of quantum computation

In this paper, we introduce two mathematical models of realistic quantum computation. First, we develop a theory of bulk quantum computation such as NMR (Nuclear Magnetic Resonance) quantum computation. For this purpose, we define bulk quantum Turing machine (BQTM for short) as a model of bulk quantum computation. Then, we define complexity classes EBQP, BBQP and ZBQP as counterparts of the quantum complexity classes EQP, BQP and ZQP, respectively, and show that EBQP=EQP, BBQP=BQP and ZBQP=ZQP. This implies that BQTMs are polynomially related to ordinary QTMs as long as they are used to solve decision problems. We also show that these two types of QTMs are also polynomially related when they solve a function problem which has a unique solution. Furthermore, we show that BQTMs can solve certain instances of NP-complete problems efficiently. On the other hand, in the theory of quantum computation, only feed-forward quantum circuits are investigated, because a quantum circuit represents a sequence of applications of time evolution operators. But, if a quantum computer is a physical device where the gates are interactions controlled by a current computer such as laser pulses on trapped ions, NMR and most implementation proposals, it is natural to describe quantum circuits as ones that have feedback loops if we want to visualize the total amount of the necessary hardware. For this purpose, we introduce a quantum recurrent circuit model, which is a quantum circuit with feedback loops. LetC be a quantum recurrent circuit which solves the satisfiability problem for a blackbox Boolean function includingn variables with probability at least 1/2. And lets be the size ofC (i.e. the number of the gates inC) andt be the number of iterations that is needed forC to solve the satisfiability problem. Then, we show that, for those quantum recurrent circuits, the minimum value ofmax(s, t) isO(n ²2 ^n/3). Tetsuro Nishino, D.Sc.: He is presently an Associate Professor in the Department of Information and Communication Engineering, The University of Electro-Communications. He received the B.S., M.S. and D.Sc degrees in mathematics from Waseda University, in 1982, 1984 and 1991 respectively. From 1984 to 1987, he joined Tokyo Research Laboratory, IBM Japan. From 1987 to 1992, he was a Research Associate of Tokyo Denki University, and from 1992 to 1994, he was an Associate Professor of Japan Advanced Institute of Science and Technology, Hokuriku. His main interests are circuit complexity theory, computational learning theory and quantum complexity theory.     

量子计算与不确定性原理

对量子计算的计算潜力的高度期望源于量子力学的各种特性,如叠加原理、纠缠现象、破坏性和建设性的量子干扰。相对于经典计算,量子计算具有某些假定的优势,例如量子算法的运行速度比经典算法快;但另一方面却似乎存在影响经典算法但不影响量子算法的障碍,障碍之一是传统上归因于Werner Heisenberg的两个不确定性原理。Heisenberg最初制定的不确定性原理涉及用于测量量子系统的非量子仪器必然会对该系统造成影响。这个原理与其后来的发展有所不同,因为后来发现的不确定性所假定的是不交换可观察量在测量方面存在固有的不能精确测量的特性。在目前的技术发展状况以及当前对量子力学的形式表述与诠释的情况下,这两种不确定性皆有可能对量子计算的速度造成不良影响。近年来,针对这两种不确定性原理有了新的研究成果:1)Ozawa对Heisenberg原理提出了修改,将两种不确定性纳入其内进行并列考虑,从而可以减小Heisenberg原理的不确定性程度;2)在考虑到熵不确定性的情况下,Heisenberg不确定性可被视为Hirschmann不确定性的下界,因此除了在测量上的不确定性之外,量子计算还必须考虑来自其他如信息学的不确定性因素。     

In Praise of Measurement

The role of measurement in quantum computation is examined in the light of John Bell’s critique of the how the term “measurement” is used in quantum mechanics. I argue that within the field of quantum computer science the concept of measurement is precisely defined, unproblematic, and forms the foundation of the entire subject.     

量子小波变换算法及线路实现

随着小波理论研究的深入,以及小波分析在信号分析和图像处理等领域的广泛应用,小波分析在量子计算领域中也越来越受到重视.应用置换矩阵、W-H变换矩阵和量子傅立叶变换矩阵来对Haar小波及D(4)小波变换矩阵进行分解,给出其算法,然后得出其完整的量子逻辑线路图,最后分析其复杂度.     

三值量子基本门及其对量子Fourier变换的电路实现

理论上可以把量子基本门组合在一起来实现任何量子电路和构建可伸缩的量子计算机。但由于构建量子线路的量子基本门数量庞大,要正确控制这些量子门十分困难。因此,如何减少构建量子线路的基本门数量是一个非常重要和非常有意义的课题。提出采用三值量子态系统构建量子计算机,并给出了一组三值量子基本门的功能定义、算子矩阵和量子线路图。定义的基本门主要包括三值量子非门、三值控制非门、三值Hadamard门、三值量子交换门和三值控制CR_k门等。通过把量子Fourier变换推广到三值量子态,成功运用部分三值量子基本门构建出能实现量子Fourier变换的量子线路。通过定量分析发现,三值量子Fourier变换的线路复杂度比二值情况降低了至少50%,表明三值量子基本门在降低量子计算线路复杂度方面具有巨大优势。     

Exponential Separation of Quantum and Classical Online Space Complexity

Although quantum algorithms realizing an exponential time speed-up over the best known classical algorithms exist, no quantum algorithm is known performing computation using less space resources than classical algorithms. In this paper, we study, for the first time explicitly, space-bounded quantum algorithms for computational problems where the input is given not as a whole, but bit by bit. We show that there exist such problems that a quantum computer can solve using exponentially less work space than a classical computer. More precisely, we introduce a very natural and simple model of a space-bounded quantum online machine and prove an exponential separation of classical and quantum online space complexity, in the bounded-error setting and for a total language. The language we consider is inspired by a communication problem (the disjointness function) that Buhrman, Cleve and Wigderson used to show an almost quadratic separation of quantum and classical bounded-error communication complexity. We prove that, in the framework of online space complexity, the separation becomes exponential.     

The Quantum Setting with Randomized Queries for Continuous Problems

The standard setting of quantum computation for continuous problems uses deterministic queries and the only source of randomness for quantum algorithms is through measurement. Without loss of generality we may consider quantum algorithms which use only one measurement. This setting is related to the worst case setting on a classical computer in the sense that the number of qubits needed to solve a continuous problem must be at least equal to the logarithm of the worst case information complexity of this problem. Since the number of qubits must be finite, we cannot solve continuous problems on a quantum computer with infinite worst case information complexity. This can even happen for continuous problems with small randomized complexity on a classical computer. A simple example is integration of bounded continuous functions. To overcome this bad property that limits the power of quantum computation for continuous problems, we study the quantum setting in which randomized queries are allowed. This type of query is used in Shor’s algorithm. The quantum setting with randomized queries is related to the randomized classical setting in the sense that the number of qubits needed to solve a continuous problem must be at least equal to the logarithm of the randomized information complexity of this problem. Hence, there is also a limit to the power of the quantum setting with randomized queries since we cannot solve continuous problems with infinite randomized information complexity. An example is approximation of bounded continuous functions. We study the quantum setting with randomized queries for a number of problems in terms of the query and qubit complexities defined as the minimal number of queries/qubits needed to solve the problem to within ɛ by a quantum algorithm. We prove that for path integration we have an exponential improvement for the qubit complexity over the quantum setting with deterministic queries.     

量子查找算法的发展与前瞻

量子查找算法是一种利用波的特性进行查找的新方法，它以量子位作为描述问题 的基本信息单位，为 NP-完全问题的解决提供了一种有效的途径。量子查找算法的主要特 点 是查找的高度并行性、非结构化查找和巨大的信息存储容量。该文介绍了量子查找的基 本思 想；综述了量子查找的典型实例及其广泛应用；分析了量子查找算法的特点及其与传 统算法 的关系；指出了量子计算目前存在的问题；最后对量子计算的发展前景进行展望。