量子计算机

简要介绍了量子计算机的基本概念及实验方案。     

神奇的量子计算机

简要地介绍了量子计算机的原理和优点,还介绍了量子计算机的一些基本概念,有量子叠加,量子纠缠,量子位、量子逻辑门和量子并行计算。     

量子计算机

较系统地阐述了量子计算机的发展和现状，着重介绍经典可逆计算机，量子可逆计算机，量子图灵机，量子计算机的构造，应用，以及当前研究热点如量子纠错和消相干问题。     

通用量子计算机和容错量子计算——概念、现状和展望

量子计算技术近年来快速发展并受到广泛关注。文章将介绍一些量子计算的基本概念、现状以及远期和近期的主要挑战,使读者可以更准确地理解一些新近的进展,避免误解。通用量子计算机的主要应用之一是破解 RSA密码。没有量子纠错,我们很难实现密码破解规模的量子计算。因此,量子计算技术的一大挑战是如何实现有量子纠错保护的量子计算,也就是容错量子计算。通过介绍现有的实验技术,将发现目前已经可以在实验中实现错误率低于容错阈值的量子门,但容错量子计算离实际应用还有距离。主要的困难在于,量子容错需要数量巨大的低错误率的量子比特,超出了现有技术能达到的水平,需要进一步的发展。有噪声中等规模量子计算有可能在近期内成为现实,目前仍有一些理论和技术方面的瓶颈问题需要深入研究。在看到量子计算技术巨大潜在价值和长足进步的同时,有必要了解有哪些亟需解决的问题,直面关键、攻坚克难。     

美国开始研制量子计算机

 十余年前,已故物理学家理查德·费曼曾有一个梦想:将量子力学中神秘的,互相矛盾着的状态充作计算工具,则其运算速度将会超过可能制造出的、速度最快的经典计算机。     

Nonadiabatic Geometric Quantum Computation with Asymmetric Superconducting Quantum Interference Device

We propose a method of controlling the dc-SQUID(superconductiong quantum interference device)system by changing the gate voltages,which controls the amplitude of the fictitious magnetic fields Bz,and the externally applied current that produces the piercing magnetic flux Φx for the dc-SQUID system,we have also introduced a physical model for the dc-SQUID system.Using this physical model,one can obtain the non-adiabatic geometric phase gate for the single qubit and the non-adiabatic conditional geometric phase gate (controlled NOT gate) for the two qubits.It is shown that when the gate voltage and the externally applied current of the dc-SQUID system satisfies an appropriate constraint condition,the charge state evolution can be controlled exactly on a dynamic phase free path.The non-adiabatic evolution of the charge states is given as well.     

量子计算与量子计算机

 最近,量子计算与量子计算机引起了人们的极大兴趣.一个光子的偏振或一个自旋为1/2的粒子(两态系统),对应于布尔态0和1,可构造量子计算机存储单元.     

第一讲 量子计算机

量子力学和计算机理论，这两个看起来互不相关的领域，其结合却产生了一门富于成效的学科；量子计算机、文章介绍了理子计算机的基本概念和历史背景，它相对于经典计算机的优越性，它的构造和实验方案，以及实现量了计算的困难及其克服途径，最后展望了量子计算机的发展前景。     

Toward a superconducting quantum computer: Harnessing macroscopic quantum coherence

Intensive research on the construction of superconducting quantum computers has produced numerous important achievements. The quantum bit (qubit), based on the Josephson junction, is at the heart of this research. This macroscopic system has the ability to control quantum coherence. This article reviews the current state of quantum computing as well as its history, and discusses its future. Although progress has been rapid, the field remains beset with unsolved issues, and there are still many new research opportunities open to physicists and engineers.     

Optimized quantum singular value thresholding algorithm based on a hybrid quantum computer

Quantum singular value thresholding (QSVT) algorithm, as a core module of many mathematical models, seeks the singular values of a sparse and low rank matrix exceeding a threshold and their associated singular vectors. The existing all-qubit QSVT algorithm demands lots of ancillary qubits, remaining a huge challenge for realization on nearterm intermediate-scale quantum computers. In this paper, we propose a hybrid QSVT (HQSVT) algorithm utilizing both discrete variables (DVs) and continuous variables (CVs). In our algorithm, raw data vectors are encoded into a qubit system and the following data processing is fulfilled by hybrid quantum operations. Our algorithm requires O[log(MN)] qubits with O(1) qumodes and totally performs O(1) operations, which significantly reduces the space and runtime consumption.     

Simulation of general three-body interactions in a nuclear magnetic resonance ensemble quantum computer

Three-body interaction plays an important role in many-body physics, and quantum computer is efficient in simulating many-body interactions. We have experimentally demonstrated the general three-body interactions in a three-qubit nuclear magnetic resonance ensemble quantum computer. Using a nuclear magnetic resonance computer we implemented general forms of three-body interactions including σ _x ¹ σ _z ² σ _x ³ and σ _x ¹ σ _z ² σ _y ³ The results show good agreement between theory and experiment. We have also given a concise and practical formula for a general n-body interaction in terms of one-and two-body interactions. Supported by the National Natural Science Foundation of China (Grant Nos. 10374010 and 10325521) and the National Basic Research Program of China (Grant No. 2006CB921106)     

Analysis and improvement of verifiable blind quantum computation

In blind quantum computation (BQC), a client with weak quantum computation capabilities is allowed to delegate its quantum computation tasks to a server with powerful quantum computation capabilities, and the inputs, algorithms and outputs of the quantum computation are confidential to the server. Verifiability refers to the ability of the client to verify with a certain probability whether the server has executed the protocol correctly and can be realized by introducing trap qubits into the computation graph state to detect server deception. The existing verifiable universal BQC protocols are analyzed and compared in detail. The XTH protocol (proposed by Xu Q S, Tan X Q, Huang R in 2020), a recent improvement protocol of verifiable universal BQC, uses a sandglass-like graph state to further decrease resource expenditure and enhance verification capability. However, the XTH protocol has two shortcomings: limitations in the coloring scheme and a high probability of accepting an incorrect computation result. In this paper, we present an improved version of the XTH protocol, which revises the limitations of the original coloring scheme and further improves the verification ability. The analysis demonstrates that the resource expenditure is the same as for the XTH protocol, while the probability of accepting the wrong computation result is reduced from the original minimum (0.866)^d* to (0.819)^d*, where d^* is the number of repeated executions of the protocol.     

From quantum cellular automata to quantum lattice gases

A natural architecture for nanoscale quantum computation is that of a quantum cellular automaton. Motivated by this observation, we begin an investigation of exactly unitary cellular automata. After proving that there can be no nontrivial, homogeneous, local, unitary, scalar cellular automaton in one dimension, we weaken the homogeneity condition and show that there are nontrivial, exactly unitary, partitioning cellular automata. We find a one-parameter family of evolution rules which are best interpreted as those for a one-particle quantum automaton. This model is naturally reformulated as a two component cellular automaton which we demonstrate to limit to the Dirac equation. We describe two generalizations of this automaton, the second, of which, to multiple interacting particles, is the correct definition of a quantum lattice gas.     

周期驱动的Harper模型的量子计算鲁棒性与量子混沌

以周期驱动的量子Harper(quantum kicked Harper, QKH)模型为例，研究复杂量子动力系统的量子计算在各种干扰下的稳定性.通过对Floquet算子本征态的统计遍历性及其Husimi函数的分析，比较随机噪声干扰和静态干扰对量子计算不同程度的影响.进一步的保真度摄动分析表明，在随机噪声干扰下保真度随系统演化呈指数衰减，而静态干扰下的保真度为高斯衰减，并通过数值计算得到了干扰下的可信计算时间尺度.与经典混沌仿真中误差使状态产生指数分离不同，量子计算对状态干扰的稳定性和仿真模型的动力学特性无关. 关键词： 量子Harper模型 量子计算 量子混沌 保真度     

Cavity control as a new quantum algorithms implementation treatment

Based on recent experiments [Nature 449, 438 (2007) and Nature Physics 6, 777 (2010)], a new approach for realizing quantum gates for the design of quantum algorithms was developed. Accordingly, the operation times of such gates while functioning in algorithm applications depend on the number of photons present in their resonant cavities. Multi-qubit algorithms can be realized in systems in which the photon number is increased slightly over the qubit number. In addition, the time required for operation is considerably less than the dephasing and relaxation times of the systems. The contextual use of the photon number as a main control in the realization of any algorithm was demonstrated. The results indicate the possibility of a full integration into the realization of multi-qubit multiphoton states and its application in algorithm designs. Furthermore, this approach will lead to a successful implementation of these designs in future experiments.     

量子计算与量子模拟

量子计算和量子模拟在过去的几年里发展迅速,今后涉及多量子比特的量子计算和量子模拟将是一个发展的重点.本文回顾了该领域的主要进展,包括量子多体模拟、量子计算、量子计算模拟器、量子计算云平台、量子软件等内容,其中量子多体模拟又涵盖量子多体动力学、时间晶体及多体局域化、量子统计和量子化学等的模拟.这些研究方向的回顾是基于对现阶段量子计算和量子模拟研究特点的考虑,即量子比特数处于中等规模而量子操控精度还不具有大规模逻辑门实现的能力,研究处于基础科研和实用化的过渡阶段,因此综述的内容主要还是希望管窥今后的发展.     

硅基集成光量子芯片技术

光量子芯片技术采用传统半导体微纳加工工艺,可在单个芯片上集成大量光量子器件,实现量子信息处理应用,具有高集成度、高精确度、高稳定性等优势。基于硅基集成光学技术的硅基光量子芯片,得益于其CMOS可兼容、非线性效应强、超高集成度等特点,在未来实现可实用化大规模光量子计算与信息处理应用方面展示出巨大潜力。文章对硅基集成光量子芯片技术进行介绍,包括硅基集成光学基础器件,硅基光量子芯片上光子的产生、操控和探测等技术,以及面向量子计算及量子信息处理应用方面大规模硅基光量子芯片技术的近期进展,并对面临的技术挑战与发展方向进行展望。