基于Java的分布式高性能计算架构

高性能计算在各个领域中的需求越来越迫切。利用闲置资源构建分布式高性能计算平台,是一种成本低廉而有效的方案。参与的便利程度是构建包含大量计算机的分布式计算平台的关键因素。提出了一种基于Java的分布式高性能计算架构。该架构中,任何空闲计算机通过网络可随时动态加入或退出计算,从而可以在短时间内构建较大规模的高性能计算平台。采用旅行商问题对架构进行了实现及验证,结果显示架构可达到较好的性能效果。     

Realization of three-qubit quantum error correction with superconducting circuits

Quantum computers could be used to solve certain problems exponentially faster than classical computers, but are challenging to build because of their increased susceptibility to errors. However, it is possible to detect and correct errors without destroying coherence, by using quantum error correcting codes. The simplest of these are three-quantum-bit (three-qubit) codes, which map a one-qubit state to an entangled three-qubit state; they can correct any single phase-flip or bit-flip error on one of the three qubits, depending on the code used. Here we demonstrate such phase- and bit-flip error correcting codes in a superconducting circuit. We encode a quantum state, induce errors on the qubits and decode the error syndrome--a quantum state indicating which error has occurred--by reversing the encoding process. This syndrome is then used as the input to a three-qubit gate that corrects the primary qubit if it was flipped. As the code can recover from a single error on any qubit, the fidelity of this process should decrease only quadratically with error probability. We implement the correcting three-qubit gate (known as a conditional-conditional NOT, or Toffoli, gate) in 63 nanoseconds, using an interaction with the third excited state of a single qubit. We find 85?±?1 per cent fidelity to the expected classical action of this gate, and 78?±?1 per cent fidelity to the ideal quantum process matrix. Using this gate, we perform a single pass of both quantum bit- and phase-flip error correction and demonstrate the predicted first-order insensitivity to errors. Concatenation of these two codes in a nine-qubit device would correct arbitrary single-qubit errors. In combination with recent advances in superconducting qubit coherence times, this could lead to scalable quantum technology.     

Preparation and measurement of three-qubit entanglement in a superconducting circuit

Traditionally, quantum entanglement has been central to foundational discussions of quantum mechanics. The measurement of correlations between entangled particles can have results at odds with classical behaviour. These discrepancies grow exponentially with the number of entangled particles. With the ample experimental confirmation of quantum mechanical predictions, entanglement has evolved from a philosophical conundrum into a key resource for technologies such as quantum communication and computation. Although entanglement in superconducting circuits has been limited so far to two qubits, the extension of entanglement to three, eight and ten qubits has been achieved among spins, ions and photons, respectively. A key question for solid-state quantum information processing is whether an engineered system could display the multi-qubit entanglement necessary for quantum error correction, which starts with tripartite entanglement. Here, using a circuit quantum electrodynamics architecture, we demonstrate deterministic production of three-qubit Greenberger-Horne-Zeilinger (GHZ) states with fidelity of 88 per cent, measured with quantum state tomography. Several entanglement witnesses detect genuine three-qubit entanglement by violating biseparable bounds by 830?±?80 per cent. We demonstrate the first step of basic quantum error correction, namely the encoding of a logical qubit into a manifold of GHZ-like states using a repetition code. The integration of this encoding with decoding and error-correcting steps in a feedback loop will be the next step for quantum computing with integrated circuits.     

High-speed linear optics quantum computing using active feed-forward

As information carriers in quantum computing, photonic qubits have the advantage of undergoing negligible decoherence. However, the absence of any significant photon-photon interaction is problematic for the realization of non-trivial two-qubit gates. One solution is to introduce an effective nonlinearity by measurements resulting in probabilistic gate operations. In one-way quantum computation, the random quantum measurement error can be overcome by applying a feed-forward technique, such that the future measurement basis depends on earlier measurement results. This technique is crucial for achieving deterministic quantum computation once a cluster state (the highly entangled multiparticle state on which one-way quantum computation is based) is prepared. Here we realize a concatenated scheme of measurement and active feed-forward in a one-way quantum computing experiment. We demonstrate that, for a perfect cluster state and no photon loss, our quantum computation scheme would operate with good fidelity and that our feed-forward components function with very high speed and low error for detected photons. With present technology, the individual computational step (in our case the individual feed-forward cycle) can be operated in less than 150 ns using electro-optical modulators. This is an important result for the future development of one-way quantum computers, whose large-scale implementation will depend on advances in the production and detection of the required highly entangled cluster states.     

网格体系结构研究

目前,网格体系结构主要有五层沙漏结构和OGSA．它们存在标准化程度低、动态性不足、分布的透明性差、应用开发模式复杂等问题．为解决这些问题,提出一种新的网格体系结构——基于虚拟计算机的网格体系,这种体系具有标准化程度高、动态性好、应用开发容易等特点,可为网格计算提供开发简单、高度分布透明的单一计算机平台．     

Embracing the quantum limit in silicon computing

Quantum computers hold the promise of massive performance enhancements across a range of applications, from cryptography and databases to revolutionary scientific simulation tools. Such computers would make use of the same quantum mechanical phenomena that pose limitations on the continued shrinking of conventional information processing devices. Many of the key requirements for quantum computing differ markedly from those of conventional computers. However, silicon, which plays a central part in conventional information processing, has many properties that make it a superb platform around which to build a quantum computer.     

A scalable quantum computer with ions in an array of microtraps

Quantum computers require the storage of quantum information in a set of two-level systems (called qubits), the processing of this information using quantum gates and a means of final readout. So far, only a few systems have been identified as potentially viable quantum computer models--accurate quantum control of the coherent evolution is required in order to realize gate operations, while at the same time decoherence must be avoided. Examples include quantum optical systems (such as those utilizing trapped ions or neutral atoms, cavity quantum electrodynamics and nuclear magnetic resonance) and solid state systems (using nuclear spins, quantum dots and Josephson junctions). The most advanced candidates are the quantum optical and nuclear magnetic resonance systems, and we expect that they will allow quantum computing with about ten qubits within the next few years. This is still far from the numbers required for useful applications: for example, the factorization of a 200-digit number requires about 3,500 qubits, rising to 100,000 if error correction is implemented. Scalability of proposed quantum computer architectures to many qubits is thus of central importance. Here we propose a model for an ion trap quantum computer that combines scalability (a feature usually associated with solid state proposals) with the advantages of quantum optical systems (in particular, quantum control and long decoherence times).     

量子计算原理及研究进展

 量子计算机是量子力学与计算问题相结合的产物,是近几年的研究热点,引起了广泛的社会关注。本文回顾量子计算机的发展,介绍了量子算法和量子计算模型,并以离子阱和超导线路为例阐述了量子计算机的物理实现,然后介绍了为了克服消相干而发展出的量子编码,以玻色取样为例讨论了量子霸权。展望未来,近期内可以展示量子霸权,进而实现解决特定问题的量子模拟器,但是普适的量子计算机的研制仍然需要很长的时间。     

Grover算法的非定域实现

用核磁共振技术目前只能做到对7个量子比特的演示计算。为此有人提出"分布式量子计算机"的方案。该文考察Grover搜索算法非定域实现,分析为实现这种非定域操作所需的Einstein-Podolsky-Rosen(EPR)纠缠对资源。以2个量子比特为例,说明非定域实现Grover搜索的全过程,并推广到N个量子比特情况下非定域实现的资源需求情况。N为要搜索数据库的大小。结果表明,某些情况下,非定域Grover算法耗用比经典Grover算法更多个EPR对,甚至比经典计算机所用的资源还多,此时的非定域量子计算失去了量子计算的优势。     

基于多变量密码体制的新型代理签名方案

目前应用广泛的代理签名体制的安全性主要是基于大数分解及离散对数难题,而这些正是量子计算影响最为深刻的领域．多变量密码作为后量子时代能够抵抗量子攻击的公钥体制之一,具有重要的研究价值．文章所设计的多变量代理签名方案就是基于多变量密码中的IP问题而提出,作为一种新的代理签名方案,其“抗量子计算”性是最大的特点,并且还具有多变量密码的实现速度快、效率高的优势     

Entanglement purification for quantum communication

The distribution of entangled states between distant locations will be essential for the future large-scale realization of quantum communication schemes such as quantum cryptography and quantum teleportation. Because of unavoidable noise in the quantum communication channel, the entanglement between two particles is more and more degraded the further they propagate. Entanglement purification is thus essential to distil highly entangled states from less entangled ones. Existing general purification protocols are based on the quantum controlled-NOT (CNOT) or similar quantum logic operations, which are very difficult to implement experimentally. Present realizations of CNOT gates are much too imperfect to be useful for long-distance quantum communication. Here we present a scheme for the entanglement purification of general mixed entangled states, which achieves 50 per cent of the success probability of schemes based on the CNOT operation, but requires only simple linear optical elements. Because the perfection of such elements is very high, the local operations necessary for purification can be performed with the required precision. Our procedure is within the reach of current technology, and should significantly simplify the implementation of long-distance quantum communication.     

并行多处理机上的具有真实感的三维图形合成

用光线跟踪来合成三维图形需要非常大的运算量，大规模的并行处理，可使合成速度得到大幅度的提高，特别是在ＭＩＭＤ机上，系统具有非常好的性能价格比，在ＭＩＭＤ机上实现三维图形的合成需要解决２个关键的问题：１）负载平衡；２）模型数据库的分解，在这篇文章中给出了一种ＭＩＭＤ机上实现三维图形合成的方法，并且提出了一种模型数据库分解的策略，根据光线跟踪一致性的特性，对各节点机的任务进行预估计，使系统的负载得到了     

基于量子测量的量子计算模型综述

基于测量的单向量子计算是重要的通用量子计算模型,可以模拟一般量子计算任务。单向量子计算基于量子簇态作为计算资源,利用每个量子位的局部量子测量和经典通信执行一般量子计算。单向量子计算是与量子线路模型等价的量子计算模型。近年来,研究者们对单向量子计算的量子资源、纠缠度量、局部操作简化,以及量子通信等给出一系列研究成果,并基于光学平台开展了一些量子模拟实验。量子簇态与单向量子计算为一般量子计算提供非常好的量子任务处理方式,受到研究者们的广泛关注。该文主要总结基于测量的单向量子计算模型,包括重要的量子资源态、局部信息处理方式,以及与单向量子计算相关的研究;该文对单向量子计算存在的问题和前沿研究方法进行展望,为研究者提供借鉴。     

Management of singlet and triplet excitons for efficient white organic light-emitting devices

Lighting accounts for approximately 22 per cent of the electricity consumed in buildings in the United States, with 40 per cent of that amount consumed by inefficient (approximately 15 lm W(-1)) incandescent lamps. This has generated increased interest in the use of white electroluminescent organic light-emitting devices, owing to their potential for significantly improved efficiency over incandescent sources combined with low-cost, high-throughput manufacturability. The most impressive characteristics of such devices reported to date have been achieved in all-phosphor-doped devices, which have the potential for 100 per cent internal quantum efficiency: the phosphorescent molecules harness the triplet excitons that constitute three-quarters of the bound electron-hole pairs that form during charge injection, and which (unlike the remaining singlet excitons) would otherwise recombine non-radiatively. Here we introduce a different device concept that exploits a blue fluorescent molecule in exchange for a phosphorescent dopant, in combination with green and red phosphor dopants, to yield high power efficiency and stable colour balance, while maintaining the potential for unity internal quantum efficiency. Two distinct modes of energy transfer within this device serve to channel nearly all of the triplet energy to the phosphorescent dopants, retaining the singlet energy exclusively on the blue fluorescent dopant. Additionally, eliminating the exchange energy loss to the blue fluorophore allows for roughly 20 per cent increased power efficiency compared to a fully phosphorescent device. Our device challenges incandescent sources by exhibiting total external quantum and power efficiencies that peak at 18.7 +/- 0.5 per cent and 37.6 +/- 0.6 lm W(-1), respectively, decreasing to 18.4 +/- 0.5 per cent and 23.8 +/- 0.5 lm W(-1) at a high luminance of 500 cd m(-2).     

基于域的自主式信任模型的研究

网格环境中的信任问题是当前网格研究的一个热点问题,为了解决网格环境的动态性和不确定性带来的安全问题,本文提出了一种新的信任模型来处理网格环境中实体之间的信任关系,该模型对域内信任关系和域间信任关系分别采取不同的方法进行处理。实验和分析结果表明,与以往的信任模型相比,这种信任模型能更加精确地评估实体之间的信任关系,从而能更加有效地解决网格环境中存在的安全问题。     

面向普适计算设备的软件体系结构

互为目的和手段的通信与计算是面向普适计算设备软件体系结构的核心问题,借鉴嵌入式Internet、网格计算、Jini的实现思想,针对其核心问题提出了一个满足动态和静态双重可配置性的面向普适计算设备的软件体系结构,以及配置和裁剪其内容使其能够运行于特定资源限制和功能性能要求系统的软件开发平台·旨在解决普适计算的设备与其提供服务的多样性与嵌入其中的计算机系统资源受限的矛盾,为普适计算的上层服务提供设备级软件体系结构上的技术保证,实现普适计算设备间互为目的和手段的通信与协作计算·     

Key-Recovery Attacks on LED-Like Block Ciphers

Asymmetric cryptographic schemes, represented by RSA, have been shown to be insecure under quantum computing conditions. Correspondingly, there is a need to study whether the symmetric cryptosystem can still guarantee high security with the advent of quantum computers. In this paper, based on the basic principles of classical slide attacks and Simon's algorithm, we take LED-like lightweight block ciphers as research objects to present a security analysis under both classical and quantum attacks, fully considering the influence on the security of the ciphers of adding the round constants. By analyzing the information leakage of round constants, we can introduce the differential of the round constants to propose a classical slide attack on full-round LED-64 with a probability of 1. The analysis result shows that LED-64 is unable to resist this kind of classical slide attack, but that attack method is not applicable to LED-128. As for quantum attacks, by improving on existing quantum attack methods we demonstrate a quantum single-key slide attack on LED-64 and a quantum related-key attack on LED-128, and indicators of the two attack algorithms are analyzed in detail. The attack results show that adding round constants does not completely improve the security of the ciphers, and quantum attacks can provide an exponential speed-up over the same attacks in the classical model. It further illustrates that the block cipher that is proved to be safe under classical settings is not necessarily secure under quantum conditions.     

计算机硬件组成架构

首先阐述了计算机硬件架构组成及其功能,基于冯＆#183;诺依曼型计算机体系结构,对现代计算机硬件组成架构进行了对比分析,分别分析了并行计算机和量子计算机的硬件组成架构。     

基于波粒二相机实现大数因子分解

利用波粒二相机,根据原始的分解算法、量子Shor算法以及经典计算机中的费马算法和莱曼算法,提出了能够进行大数因子分解的几种算法.通过对原始分解算法的改进,使得用原始大数因子分解的问题由N次变为1次完成.通过对费马算法和莱曼算法改进,减少了大数质因子分解过程的计算复杂度.与量子计算机相比,波粒二相机使得在经典上需要指数步完成的算法,在多项式时间内就可以解决,减少了计算复杂度.     

云计算与网格计算比较研究

云计算作为下一代计算模式,在科学计算和商业计算领域发挥着重要作用,受到当前学术界和企业界的广泛关注.云计算不同于传统的以个人计算机为中心的本地计算,它以互联网为中心,通过构建一个或多个由大量普通机器和网络设备连接的数据中心,把海量的数据存储到数据中心上,向上层的服务和应用提供安全、可靠、快捷、透明的数据存储和计算服务.根据国内外相关文献,通过对云计算和网格计算在体系结构、计算模型、编程模型方面进行了深入的讨论,对云计算的概念有更准确和深入的了解.