我国首个量子计算机操作系统在合肥发布

正2月8日晚,首款国产量子计算机操作系统——"本源司南"在合肥市正式发布。该系统由合肥本源量子计算科技有限责任公司自主研发,实现了量子资源系统化管理、量子计算任务并行化执行、量子芯片自动化校准等全新功能,助力量子计算机高效稳定运行,标志着国产量子软件研发能力已达国际先进水平。相比于经典计算机,量子计算机最突出的优势在于强大的计算能力,但目前全球范围内可供使用的量子计算机只有50台左右,如果不能做到有效利用,就会出现算力浪费情况。     

量子计算机原理

本以与经典计算机对照的方法，介绍量子图灵机、量子位、量子寄存器、量子逻辑门、量子并行计算和量子编码，从量子计算机的物理和工作原理阐明量子计算机的优越性。     

大数据与量子计算

大数据技术的迅猛发展对计算效率提出了更高的要求.由于量子系统的独特性质,量子计算具有经典计算不具有的量子超并行计算能力,能够对某些重要的经典算法进行加速.人们发现,除了大数分解算法,量子计算的更多用途是对量子体系的仿真计算和在数据分析领域的应用.近年来,大数据和量子计算开始融合.虽然实际使用的量子计算机尚未建成,量子计算在大数据的应用在理论上已经取得了一些重要的进展.实验上也有了一些发展.本文首先介绍量子计算的基本原理和Grover量子算法.随后以量子机器学习作为切入点,介绍了量子计算在数据挖掘领域的应用.     

关于量子算法理论

本文讨论在量子计算机上进行量子计算的方法。重点讨论Shor的量子因子分解方法。经典的大数因子分解对所有的现行计算机而言是难解的。现在通用的公共加密系统正是利用这一困难作为加密的基础。但是，在量子计算机上进行的Shor量子算法，使大数因子分解不再是难解的而是有效的，因而可能对现在通用的公共加密系统形成挑战。本文介绍在量子计算机上进行的Shor量子算法，即利用量子态的相干叠加和纠缠特性以及量子逻辑门实现量子计算的方法：并着重从理论原理和实验实现这两方面说明利用余因子函数和分立福里叶变换使这种量子算法对因子分解是有效的。     

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。     

量子计算机的核心与发展

分析、对比了经典计算机和量子机的异同，讨论了量子计算机的核心与发展趋势，指出经典计算机和量子计算机的结构结合将是计算机发展的最佳模式。     

超导电荷量子比特研究综述

随着量子计算机以及量子算法的提出，人们开始寻找可以实现量子计算机的真实物理体系。超导量子电路以其丰富的可设计性和优良的易集成性成为最有潜力实现量子计算机的人造量子体系。文章介绍了超导电荷量子比特的基本原理、超导电荷量子比特的耦合以及耗散和退相干问题，展望了超导电荷量子比特在量子计算和量子信息科学中的应用前景。     

基于IBM Q平台的量子图像算法研究

为使量子图像处理算法在量子计算机上得到验证与发展,结合IBM量子实验平台(IBM Q)上量子计算操作与量子图像处理理论的研究,设计了一种基于IBM Q平台的量子图像分割方法.提出了一种基于新型强化量子图像表达式(NEQR)的改进型强化量子图像表达式(IEQR),并根据IEQR表达式初始化量子图像分割电路.该电路由量子比较器(QBSC)和受控旋转门(Cswap)构成.最终在IBM Q和本地经典计算机仿真两种平台下实现了2×2和4×4大小的量子图像分割,实验结果表明了该算法的可行性和有效性,并验证了量子计算机的优越性.     

基于金刚石体系的固态量子计算

量子计算科学是近年来物理学领域最活跃的研究前沿之一,其开拓了与经典方式具有本质区别的全新的信息处理模式.量子计算研究的根本目标是建造基于量子力学基本原理的量子信息处理技术,能在许多复杂计算问题上大大超越经典计算性能的新型计算模式.量子计算需要一个良好的量子体系作为载体.基于自旋的量子体系由于其实用的可操作性,成为量子计算载体的优秀候选.自旋的所有量子性质表现在自旋的叠加态、自旋之间的纠缠和对自旋的量子测量上.基于系综的量子计算演示实验已经被多次实现,但是系综体系在可扩展性上有其原理上的缺陷.要实现可扩展的大规模室温固态量子信息处理和量子计算的突破,实现单量子态的寻址和读出是一个最重要的前提.在已经提出的单自旋固态量子计算载体中,比较突出的一类是基于金刚石中的氮-空位色心单电子自旋体系.金刚石中的氮-空位色心单电子自旋量子态可以在室温下初始化、操控与读出,成为室温量子计算机载体的优良候选者.我们首先回顾金刚石氮-空位色心单电子自旋体系作为量子计算机载体的重要进展;然后讨论了该体系在纳米尺度灵敏探测和成像方面的重要应用;最后,描述了此领域的前景.     

信息科学的未来——量子计算机

阐述了量子计算机产生的背景及目前发展状况,分析了量子计算机的基本原理及量子平行计算在信息处理上的优势.     

Experimental demonstration of topological error correction

Scalable quantum computing can be achieved only if quantum bits are manipulated in a fault-tolerant fashion. Topological error correction--a method that combines topological quantum computation with quantum error correction--has the highest known tolerable error rate for a local architecture. The technique makes use of cluster states with topological properties and requires only nearest-neighbour interactions. Here we report the experimental demonstration of topological error correction with an eight-photon cluster state. We show that a correlation can be protected against a single error on any quantum bit. Also, when all quantum bits are simultaneously subjected to errors with equal probability, the effective error rate can be significantly reduced. Our work demonstrates the viability of topological error correction for fault-tolerant quantum information processing.     

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.     

Realization of quantum error correction

Scalable quantum computation and communication require error control to protect quantum information against unavoidable noise. Quantum error correction protects information stored in two-level quantum systems (qubits) by rectifying errors with operations conditioned on the measurement outcomes. Error-correction protocols have been implemented in nuclear magnetic resonance experiments, but the inherent limitations of this technique prevent its application to quantum information processing. Here we experimentally demonstrate quantum error correction using three beryllium atomic-ion qubits confined to a linear, multi-zone trap. An encoded one-qubit state is protected against spin-flip errors by means of a three-qubit quantum error-correcting code. A primary ion qubit is prepared in an initial state, which is then encoded into an entangled state of three physical qubits (the primary and two ancilla qubits). Errors are induced simultaneously in all qubits at various rates. The encoded state is decoded back to the primary ion one-qubit state, making error information available on the ancilla ions, which are separated from the primary ion and measured. Finally, the primary qubit state is corrected on the basis of the ancillae measurement outcome. We verify error correction by comparing the corrected final state to the uncorrected state and to the initial state. In principle, the approach enables a quantum state to be maintained by means of repeated error correction, an important step towards scalable fault-tolerant quantum computation using trapped ions.     

去极化信道的多次量子纠错

本文利用量子过程层析成像建立了一个适用于多次量子纠错的通用方案,以去极化信道为例,说明了此方案的可行性.发现单次纠错之后等价量子噪声信道.依然可以看作是保真度提高的去极化信道,且保真度的提高有着严格的解析表达式.在对初始信道保真度要求不高的情况下,能够很好地实现多次纠错,让其保真度达到需要的精度.     

Deleting a marked state in quantum database in a duality computing mode

In this article, we present a deletion algorithm in the duality computer that deletes a marked state from an even superposition of all basis-states with certainty. This duality computer deletion algorithm requires a single query, and this achieves exponential speedup over classical algorithm. Using a duality mode and recycling quantum computing, we provide a realization of this duality computer deletion algorithm in quantum computer.     

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.     

奇偶-汉明纠错算法性能及其误码率估计仿真分析

量子密钥分发需要借助量子信道和经典信道共同完成,量子信道传输中不完美的装置和噪声的影响以及第三方的窃听,使得原始密钥具有高的误码率,需要借助经典信道来进行误码协调,完成纠错。以分组纠错码中的汉明码为研究对象,仿真分析汉明码纠错的密钥生成效率与初始误码率和不同码字长度之间的关系,同时完成误码率的估计。结果表明在误码率较高时,使用短码,在误码率较低时,使用长码,可以提高密钥的生成效率,而误码率的高低以估计误码率为依据。     

Quantum computing with realistically noisy devices

In theory, quantum computers offer a means of solving problems that would be intractable on conventional computers. Assuming that a quantum computer could be constructed, it would in practice be required to function with noisy devices called 'gates'. These gates cause decoherence of the fragile quantum states that are central to the computer's operation. The goal of so-called 'fault-tolerant quantum computing' is therefore to compute accurately even when the error probability per gate (EPG) is high. Here we report a simple architecture for fault-tolerant quantum computing, providing evidence that accurate quantum computing is possible for EPGs as high as three per cent. Such EPGs have been experimentally demonstrated, but to avoid excessive resource overheads required by the necessary architecture, lower EPGs are needed. Assuming the availability of quantum resources comparable to the digital resources available in today's computers, we show that non-trivial quantum computations at EPGs of as high as one per cent could be implemented.     

基于BDD的Grover算法仿真

为了解决仿真量子计算过程中复杂性随量子比特数的增加呈指数级递增的问题,采用二项决策图(BDD)表示矩阵算子仿真Grover提出的量子搜索算法.BDD利用矩阵算子在量子计算过程中呈现出的结构化特性,可以高效地压缩存储空间并实现在压缩数据结构上直接进行矩阵的各种运算.利用改进的BDD实现了仿真过程需要的各种矩阵运算,用C++编写的程序对Grover算法的实例进行仿真,最后从多个角度对违反直观的实验结果进行了分析,阐述了量子算法的内在并行性.