基于纯态的量子通信系统模型

量子通信与量子计算已经引起人们极大的关注.对于量子态如何用于信息处理的问题,提出了量子通信的两种基本模型:量子直接通信模型与量子隐形传态通信模型.在量子直接通信模型中,用模块化的方法将量子通信全过程分为量子信源编译码,量子信道编译码,量子信道与量子噪声模块,并详细阐述了各个模块的功能与用途.在量子隐形传态通信模型中,利用量子隐形传态特性,通过将待传粒子与纠缠对的联合测量模块化为量子调制部分,给出了基于隐形传态的量子通信一般模型.量子通信在安全性及效率方面具有经典通信无法比拟的优势.     

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。     

一维量子卷积计算

研究了一维信息编码为量子态后进行量子卷积计算的量子线路模型。基于量子图像表示和经典信息的卷积算法,设计出了一维量子卷积计算的量子线路结构,表明量子卷积计算可以以[O(n2)]的复杂度计算卷积。与经典卷积相比,量子卷积计算由于利用量子并行计算在计算速率上达到了指数级的加速,为量子卷积神经网络卷积层的设计实施作铺垫。     

Quantum estimation,control and learning: Opportunities and challenges

The development of estimation and control theories for quantum systems is a fundamental task for practical quantum technology. This vision article presents a brief introduction to challenging problems and potential opportunities in the emerging areas of quantum estimation, control and learning. The topics cover quantum state estimation, quantum parameter identification, quantum filtering, quantum open-loop control, quantum feedback control, machine learning for estimation and control of quantum systems, and quantum machine learning.     

量子程序设计语言NDQJava-2

简述了量子程序设计语言NDQJava-2.该语言是在NDQJava的基础上增添了量子条件语句、量子循环语句、量子子程序、量子模块以及量子异常处理机制等量子成分,使其成为一种结构化的量子程序设计语言.书写量子程序的实践表明,相对于NDQJava而言,NDQJava-2是一种更为实用、易读,其成分设定更为合适的量子程序设计...     

量子态估计简介及其在超导电路电动力学系统中的应用

量子态估计是量子计算以及量子调控的基础,一般分为量子态层析,即对未知量子态(或过程的初态)进行估计,以及量子滤波,即对量子态进行实时的估计.本文首先介绍了近年来量子态层析技术新的进展,内容包括极大似然方法,压缩感知方法和线性回归方法,并分析了它们的适用范围及各自的优缺点.进一步,基于量子计算的成熟载体超导电路电动力学系统,介绍了基于连续弱测量对量子态进行实时估计的贝叶斯方法,并分析了贝叶斯估计的适用情形.进一步,通过仿真实现了量子贝叶斯估计,可以很容易发现贝叶斯方法能够精确地实时追踪量子态的演化.     

Quantum probabilistically cloning and computation

In this article we make a review on the usefulness of probabilistically cloning and present examples of quantum computation tasks for which quantum cloning offers an advantage which cannot be matched by any approach that does not resort to it. In these quantum computations, one needs to distribute quantum information contained in states about which we have some partial information. To perform quantum computations, one uses state-dependent probabilistic quantum cloning procedure to distribute quantum information in the middle of a quantum computation. And we discuss the achievable efficiencies and the efficient quantum logic network for probabilistic cloning the quantum states used in implementing quantum computation tasks for which cloning provides enhancement in performance.     

Quantum correlation via quantum coherence

Quantum correlation includes quantum entanglement and quantum discord. Both entanglement and discord have a common necessary condition—quantum coherence or quantum superposition. In this paper, we attempt to give an alternative understanding of how quantum correlation is related to quantum coherence. We divide the coherence of a quantum state into several classes and find the complete coincidence between geometric (symmetric and asymmetric) quantum discords and some particular classes of quantum coherence. We propose a revised measure for total coherence and find that this measure can lead to a symmetric version of geometric quantum correlation, which is analytic for two qubits. In particular, this measure can also arrive at a monogamy equality on the distribution of quantum coherence. Finally, we also quantify a remaining type of quantum coherence and find that for two qubits, it is directly connected with quantum nonlocality.     

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。     

量子纠缠遗传算法在微带耦合器中的应用

结合量子纠缠理论,提出了量子纠缠遗传算法。利用多粒子的量子纠缠W态,探讨了量子染色体的纠缠编码方式;给出了量子更新算符、量子变异算符和量子交叉算符的具体形式;给出了量子纠缠遗传算法的具体步骤。最后,将量子纠缠遗传算法应用到微带耦合器设计中,其结果表明量子纠缠遗传算法优化速度很快,能够得到很好的优化结果。     

利用立方图的线图构造量子纠错码

量子纠错码在量子通信和量子计算中起着非常重要的作用,之前的量子纠错码的构造大部分都是利用经典的纠错码来构造得到,如Hamming码,BCH码,RS码,Reed-Muller码等各种经典纠错码。目前,很少有人利用图生成的线性码方法来构造量子纠错码,提出了一个新的构造量子纠错码和非对称量子纠错码的方法,即利用[n]立方图的线图生成的二元线性码来构造量子纠错码和非对称量子纠错码,得到了一类新的量子纠错码和非对称量子纠错码,并且,当码字的长度较大时,对所构造的非对称量子纠错码,在非对称信道上有更大的纠错能力。     

Multi-strategy based quantum cost reduction of linear nearest-neighbor quantum circuit

With the development of reversible and quantum computing, study of reversible and quantum circuits has also developed rapidly. Due to physical constraints, most quantum circuits require quantum gates to interact on adjacent quantum bits. However, many existing quantum circuits nearest-neighbor have large quantum cost. Therefore, how to effectively reduce quantum cost is becoming a popular research topic. In this paper, we proposed multiple optimization strategies to reduce the quantum cost of the circuit, that is, we reduce quantum cost from MCT gates decomposition, nearest neighbor and circuit simplification, respectively. The experimental results show that the proposed strategies can effectively reduce the quantum cost, and the maximum optimization rate is 30.61% compared to the corresponding results.     

量子投影滤波

量子滤波器基于贝叶斯原理,利用连续弱测量数据给出当前时刻量子系统状态的最优估计,是量子计算和量子调控技术中极为重要的一环.然而,随着量子系统能级数提高,量子滤波器的实时计算复杂度呈二次型增长.本文介绍了一种量子投影滤波方法,用于减少量子滤波器的实时计算复杂度.基于量子信息几何方法,量子轨迹被限制在了一个由一类非归一化量子密度矩阵组成的子流形中.量子态从而可通过计算子流形的坐标系统来近似获得.仿真实验说明了投影滤波方法的有效性.     

基于量子逻辑的图灵机及其通用性

基于量子逻辑的自动机理论是量子计算模型的一个重要研究方向.该文研究了基于量子逻辑的图灵机(简称量子图灵机)及其一些变形,给出了包括非确定型量子图灵机l-VTM,确定型量子图灵机l-VDTM以及相应类型的多带量子图灵机,并引入量子图灵机基于深度优先与宽度优先识别语言的两种不同定义方式,证明了这两种定义方式在量子逻辑意义下是不等价的.进一步证明了l-VTM、l-VDTM与相应类型的多带量子图灵机之间的等价性.其次,给出了量子递归可枚举语言及量子递归语言的定义,并给出了二者的层次刻画,证明了l-VTM与l-VDTM不等价,但两者作为量子递归语言的识别器是等价的.最后,文中讨论了基于量子逻辑的通用图灵机的存在性问题,给出了一套合理编码系统,证明了基于量子逻辑的通用图灵机在其所取值的正交模格无限时不存在,而在其所取值的正交模格有限时是存在的.     

多值逻辑量子置换门的酉矩阵表示

理论上量子可逆电路不存在能量耗散问题,因此量子计算系统对环境产生的负面影响可以达到最低.多值逻辑量子置换门是构建多值逻辑量子电路的基本单元.该文从数学的角度研究多值逻辑量子置换门的酉矩阵,提出了一种构造多值逻辑量子置换门酉矩阵的方法,并对其正确性进行了讨论.在此基础之上,又给出了构造混合多值逻辑量子置换门酉矩阵的框架,利用此框架可以方便地构造任何混合逻辑量子置换门的酉矩阵.酉矩阵是量子门的数学模型,可以清晰地反映出量子门的数学性质.研究量子门的酉矩阵对验证量子门的正确性和可靠性,分析量子状态在电路中的演化过程及发展趋势具有一定的意义.     

Quantum Fisher information,quantum entanglement and correlation close to quantum critical phenomena

In this paper, we investigate the quantum Fisher information (QFI), quantum entanglement, quantum correlation and quantum phase transition (QPT) within the one-dimensional transverse Ising model by exploiting quantum renormalization-group method. The results show that quantum Fisher information, quantum entanglement, quantum correlation can evolve to two saturated values which exhibit QPT at the critical point after several iterations of the renormalization. Meanwhile, we find quantum entanglement or correlation can be detected perfectly by means of quantum Fisher information. Besides, it cannot capture any information about the system in the paramagnetic phase in view of quantum entanglement and correlation. Contrarily, it is evident the QFI is always nonzero even if the system is in the paramagnetic phase, i.e., the QFI can also be utilized as a highly favorable measure of quantum information in a broad of quantum spin systems. Furthermore, we disclose the nonanalytic and scaling behaviors of quantum Fisher information, which can be taken as a representation of quantum critical characterism.     

基于光量子芯片的量子自旋链中完美态转移可编程量子模拟

近些年,量子计算物理实现技术进步很快,构建能够发挥实际用途的量子计算装置成为发展重点。采用量子模拟研究量子自旋系统的演化行为,相比于经典模拟会更加高效。一维量子自旋链中完美态转移模型在量子通信和量子计算领域具有重要的研究价值。提出一种基于双光子连续时间量子漫步的可编程完美态转移量子模拟方法,并且基于光量子芯片完成了2类特殊哈密顿量作用下XY型量子自旋链中双激发“周期-镜像”完美态转移的量子模拟实验,为模拟量子自旋系统的演化提供了一种实用且可扩展的实验方案。     

Editorial

Quantum technology is recognized as one of the most promising directions for our future technologies. By exploiting the unique features of quantum effects, emerging quantum technology is rapidly progressing around the world including quantum computation, quantum communication, quantum metrology and quantum simulation. The development of quantum control plays a grounding role in enabling the preservation and manipulation of quantum states that are used in various quantum technologies. This special issue will focus on new development in relevant topics of estimation and control methods in quantum systems, and provide a forum for idea exchange in this dynamic research area. Particularly, Ian R. Petersen, a key figure in the development of robust and quantum control theory, just turned 60 in the past year. We propose to celebrate this occasion with this special issue on quantum control, one of his main research focuses in the last fifteen years....     

VENUS: A Geometrical Representation for Quantum State Visualization

Visualizations have played a crucial role in helping quantum computing users explore quantum states in various quantum computing applications. Among them, Bloch Sphere is the widely-used visualization for showing quantum states, which leverages angles to represent quantum amplitudes. However, it cannot support the visualization of quantum entanglement and superposition, the two essential properties of quantum computing. To address this issue, we propose VENUS, a novel visualization for quantum state representation. By explicitly correlating 2D geometric shapes based on the math foundation of quantum computing characteristics, VENUS effectively represents quantum amplitudes of both the single qubit and two qubits for quantum entanglement. Also, we use multiple coordinated semicircles to naturally encode probability distribution, making the quantum superposition intuitive to analyze. We conducted two well-designed case studies and an in-depth expert interview to evaluate the usefulness and effectiveness of VENUS. The result shows that VENUS can effectively facilitate the exploration of quantum states for the single qubit and two qubits.     

Multi-image encryption scheme based on quantum 3D Arnold transform and scaled Zhongtang chaotic system

A quantum representation model for multiple images is firstly proposed, which could save more storage space than the existing quantum image representation models and allow quantum hardware to encrypt an arbitrary number of images simultaneously. Moreover, the definition and the quantum circuit of quantum 3D Arnold transform are given based on the proposed quantum representation model for multiple images. Furthermore, a novel quantum multi-image encryption scheme is devised by combining quantum 3D Arnold transform and quantum XOR operations with scaled Zhongtang chaotic system. Theoretically, the proposed quantum image encryption scheme could encrypt many images simultaneously. Numerical simulations and theoretical analyses demonstrate that the proposed quantum multi-image encryption scheme outperforms both its classical counterparts and the existing typical quantum image encryption algorithms in terms of security, robustness, encryption capacity and computational complexity.