Mesoscopic Continuous and Discrete Channels for Quantum Information Transfer

We study the possibility of realizing perfect quantum state transfer in mesoscopic devices. We discuss the case of the Fano-Anderson model extended to two impurities in a single excitation regime. For a channel with an infinite number of degrees of freedom, we obtain coherent behaviour in the case of strong coupling or in weak coupling off-resonance. For a finite number of degrees of freedom, coherent behaviour is associated to weak coupling and resonance conditions.     

On Classification of Quantum Channels

Quantum mutual entropy and quantum capacity are rigorously defined by Ohya, and they are quite useful in the study of quantum communication processes. Mathematical models of optical communication processes are described by a quantum channel and optical states, and quantum capacity is one of the most important criteria to measure the efficiency of information transmission. In actual optical communication, a laser beam is used for a signal, and it is denoted mathematically by a coherent state. Further, optical communication using a squeezed state, which is expected to be more efficient than that using a coherent state is proposed. In this paper, we define several quantum channels, that is, a squeezed channel and a coherent channel and so on. We compare them by calculating quantum capacity.     

Parametrizing Quantum States and Channels

This work describes one parametrization of quantum states and channels and several of its possible applications. This parametrization works in any dimension and there is an explicit algorithm which produces it. Included in the list of applications are a simple characterization of pure states, an explicit formula for one additive entropic quantity which does not require knowledge of eigenvalues, and an algorithm which finds one Kraus operator representation for a quantum operation without recourse to eigenvalue and eigenvector calculations. PACS: 03.67a, 03.67-Hk, 03.67-Lx     

Quantum Ergodic Theory and Communication Channels

The recently developed theory of the noncommutative dynamical entropy is applied to the theory of quantum communication channels. It is argued that the speed of information transmission is bounded by the dynamical entropy of the information carrier treated as a quantum dynamical system. The proof is given for two classes of communication channels. For the first one the input and output are classical devices which produce strings of bits, while for the second one the input and output messages are quantum states.     

Estimation of Quantum Channels with Finite Resources

We examine the problem of determining the parameters that describe a quantum channel. It is assumed that the users of the channel have at best only partial knowledge of it and make use of a finite amount of resources to estimate it. We discuss simple protocols for the estimation of the parameters of several classes of channels that are studied in the current literature. A quantitative measures of the quality of the estimation schemes can be given on the basis of the standard deviation or of the fidelity. Protocols that employ entangled particles are also discussed. The use of entangled particles as a nonclassical resource enhances the estimation quality of some classes of quantum channel. Further, the methods presented here can be extended to higher dimensional quantum systems. PACS: 03.67.Hk     

一种新的量子噪声信道仿真算法

为了实现量子密钥分配协议在几种不同的量子噪声信道上的仿真分析。基于量子力学的有关知识。通过密度矩阵的变化。依靠数学方法，推出量子态在发送和接收期间的变化，提出一个量子噪声信道模型的新算法，相对其他基于密度矩阵的算法而言．能更直观．更简单的实现量子密钥分配协议在计算机上的仿真。     

Quantum Solution of Coordination Problems

We present a quantum solution to coordination problems that can be implemented with existing technologies. Using the properties of entangled states, this quantum mechanism allows participants to rapidly find suitable correlated choices as an alternative to conventional approaches relying on explicit communication, prior commitment or trusted third parties. Unlike prior proposals for quantum games our approach retains the same choices as in the classical game and instead utilizes quantum entanglement as an extra resource to aid the participants in their choices.     

Spin-Based Quantum Information Processing in Magnetic Quantum Dots

We define the qubit as a pair of singlet and triplet states of two electrons in a He-type quantum dot (QD) placed in a diluted magnetic semiconductor (DMS) medium. The molecular field is here essential as it removes the degeneracy of the triplet state and strongly enhances the Zeeman splitting. Methods of qubit rotation as well as two-qubit operations are suggested. The system of a QD in a DMS is described in a way which allows an analysis of the decoherence due to spin waves in the DMS subsystem.on leave from Institute of Physics, Odessa UniversityPresented at the 36th Symposium on Mathematical Physics, “Open Systems & Quantum Information”, Toruń, Poland, June 9–12, 2004.     

Quantum Communication and Information Processing with Quantum Dots

This paper reviews the single photon sources based on semiconductor quantum dots and their applications to quantum information systems. By optically pumping a system consisting of a semiconductor single quantum dot confined in a monolithic microcavity, it is possible to produce a single photon pulse stream at the Fourier transform limit with a negligible jitter. This single photon source is not only useful for BB84 quantum key distribution (QKD), but also find applications in other quantum information systems such as Ekert91/BBM92 QKD and quantum teleportation gate linear optical quantum computers.     

The Multifarious Quantum Information

This paper considers the scope and possibilities of quantum information within the consensus interpretation of the theory. It is pointed out that a prepared quantum state offers a multitude of answers determined by the query directed to it. It predicts the outcome of measurements of alternative observations or allows the performance of a selection of quantum information processes. Knowing the state does not determine which observables can be assigned values, but defining a point of view of the observer allows him to derive outcomes of measurements. However, all predictions are in the form of statistical distributions or correlations between observations. Thus they are intrinsically independent of separations in space and time: like all statistical knowledge they have to be reassessed when new infomation imposes a new initial state. Many properties determined by quantum observations must be assigned to the results of the measurements and not to the physical system itself. Thus the property of nonlocality is a consequence of the probabilistic interpretation only, and it corresponds to no feature assigned to the physical reality.     

Multimedia Information Delivery Over Wireless Channels

Wireless communication channels are generally characterized by availability of low bandwidth. Hence, exchange of multimedia information is normally done over a single or unicast channel. Multimedia information presentation can have certain constraints, such as precedence of one page of information with respect to another or the time of availability of information. Multimedia information delivery needs to be scheduled based on these constraints. In this paper, we model this scheduling problem using linear programming approach. We suggest the use of approximation algorithms proposed for this purpose (L.A. Hall, A.S. Schulz, D.R. Shmoys, and J. Wein, Mathematics of Operations Research, Vol. 22, pp. 513–544, 1997). We have also presented the use of on-line approximation algorithms for scheduling multimedia information delivery when their availability varies with time. We have presented our implementation experience also.     

Quantum Algorithms for Matching Problems

We present quantum algorithms for the following matching problems in unweighted and weighted graphs with n vertices and m edges:

单可表示类的特征

择优模型是目前常识推理领域中最常用的语义结构之一。在择优模型中有一类重要的模型－单射择优模型,近年来,众多的学者对该模型类从各种角度进行了研究,但一个重要而基本的问题,即何种类型的择优后承具有单射择优模型,虽经多位学者的研究到现在仍然悬而未解。目前,最好的结果Freund在有限语言限制下证明了“择优后承具有单射择优模型当且仅当它满足弱析取合理性”。文中提出择优模型的一种转换,将此转换应用于Kraus,Leham及Magidor提出的KLM模型上,在一般语言框架下证明了“满足弱析取合理性的择优后承必具有单射择优模型”,从而将该问题的研究推进了一步。     

Quantum Computing and Information Extraction for Dynamical Quantum Systems

We discuss the simulation of complex dynamical systems on a quantum computer. We show that a quantum computer can be used to efficiently extract relevant physical information. It is possible to simulate the dynamical localization of classical chaos and extract the localization length with quadratic speed up with respect to any known classical computation. We can also compute with algebraic speed up the diffusion coefficient and the diffusion exponent, both in the regimes of Brownian and anomalous diffusion. Finally, we show that it is possible to extract the fidelity of the quantum motion, which measures the stability of the system under perturbations, with exponential speed up. The so-called quantum sawtooth map model is used as a test bench to illustrate these results. PACS: 03.67.Lx, 05.45.Mt     

量子假设检验互信息

von Neumann互信息是Shannon互信息在量子信息中的推广,在量子信道容量中有非常好的应用.由于量子态的非对易性,许多经典信息论中的量化在量子信息中有完全不等价的推广定义.量子假设检验相对熵来自于假设检验问题,是量子信息处理中常用的基本量化之一.使用量子假设检验相对熵讨论量子互信息. 首先讨论量子假设检验相对熵的一些基本性质,并给出该量化和其他量子广义熵之间的关系. 然后结合相对熵的性质,给出量子假设检验互信息的定义,并讨论其性质,比如：数据处理不等式.通过互信息与条件熵之和重点讨论互信息的链式法则.     

Duality in Quantum Information Geometry

Let H be a separable Hilbert space. We consider the manifold M consisting of density operators on H such that ^p is of trace class for some p (0, 1). We say M is nearby if there exists C > 1 such that C ^–1C. We show that the space of nearby points to can be furnished with the two flat connections known as the (±)-affine structures, which are dual relative to the BKM metric. We furnish M with a norm making it into a Banach manifold.     

Quantum Information Processing in Cavity-QED

We give a brief overview of cavity-QED and its roles in quantum information science. In particular, we discuss setups in optical cavity-QED, where either atoms serve as stationary qubits, or photons serve as flying qubits. PACS: 42.50.Pq, 03.67.Lx, 03.67.Hk, 32.80.Pj     

量子图像处理问题综述

量子图像处理问题将是量子计算机时代媒体信息处理的一个主要问题。量子图像处理包括一般的处理问题和安全方面的处理问题。本文介绍和分析了量子图像表示方式和处理等问题的最新研究成果。首先给出了目前量子图像处理的一般架构,然后介绍了目前流行的量子图像表示方法、并根据不同的量子图像处理目的对现有的处理算法进行了分类和分析,最后总结并展望了量子图像处理领域的未来发展方向。     

视频字符叠加器叠加芯片比较

字符叠加（0sD）是一种在视频电子信号中叠加字符信息,使得电视图像中叠加有字符或汉字图形的技术。目前这项技术的应用极其广泛,因此,针对这种需求,结合市场最新技术对实现视频字符叠加进行研究与设计。文章论述了视频字符叠加的原理,并描述了目前市场上流行的叠加芯片的技术指标,就不同的芯片的不同的方案提出分析论证：着重了解MB90092、UPD6453和MAX7456方案的特性与使用方法。