Quantum Correlations in a Generalized Spin Star System

The problem of detecting quantum signatures in the correlations formed in dynamical evolution of quantum bipartite systems receives a lot of attention in current literature. Generally speaking, the occurrence of correlations between two observables of a system does not necessarily reflect nonclassical behaviour. In this paper, the exact dynamics of a pair of uncoupled spins 1/2 interacting with a common spin 1/2 bath is investigated. Starting from a separable initial condition, the ability of the system to develop purely quantum correlations is brought to light. Physical interpretation of the concurrence function as well as a suggestion on how to measure it are given.     

Further Results on the Observability of Quantum Systems Under General Measurement

In this paper, we present a collection of results on the observability of quantum mechanical systems, in the case the output is the result of a discrete nonselective measurement. By defining an effective observable, we extend previous results, on the Lie algebraic characterization of observable systems, to general measurements. Further results include the characterization of a ‘best probe’ (i.e. a minimally disturbing probe) in indirect measurement and a study of the relation between disturbance and observability in this case. We also discuss how the observability properties of a quantum system relate to the problem of state reconstruction. Extensions of the formalism to the case of selective measurements are also given.     

Quantum Logic and Quantum Theory in a Game-Theoretic Perspective

Extensive games of imperfect information, together with the associated semantic machinery, can be brought to bear on logical aspects of quantum-theoretic phenomena. Among other things, this kinship implies that propositional logic of informational independence is useful in understanding such quantum theoretic issues as non-locality and EPR-type paradoxes, and that quantum logic exhibits the overall game-theoretical notion of uncertainty.     

量子测量与量子计算

本文的讨论主要集中在量子力学中测量部分,首先从量子力学的几大公设出发,着重分析测量公设的含义。然后提出量子力学争论的焦点问题之一——测量问题,并通过分别阐述塌缩原理、非塌缩原理以及对二者的比较来分析各种说法的合理性。接下来简要讨论同时测量问题。最后简略描述测量在不同量子计算模型中的体现,并对测量带来的问题做了思考。     

Quantum and Classical Correlations of Spatial and Spin Degrees of Freedom in Quantum Rings

A one-dimensional mesoscopic ring with one input and two output leads acts as a spintronic beam splitter. The spatial degree of freedom, i.e., the presence of two different possible output channels, gets intertwined with the spin direction as a consequence of quantum interference and spin-orbit interaction. We investigate this kind of spatial-spin correlation, and show that the output density operator contains no quantum entanglement in the important special case when the device polarizes a perfectly random input spin state. However, the correlations are in general not purely classical, we also present specific input states with maximal spatial-spin entanglement after the ring.     

Quantum Set Theory Extending the Standard Probabilistic Interpretation of Quantum Theory

The notion of equality between two observables will play many important roles in foundations of quantum theory. However, the standard probabilistic interpretation based on the conventional Born formula does not give the probability of equality between two arbitrary observables, since the Born formula gives the probability distribution only for a commuting family of observables. In this paper, quantum set theory developed by Takeuti and the present author is used to systematically extend the standard probabilistic interpretation of quantum theory to define the probability of equality between two arbitrary observables in an arbitrary state. We apply this new interpretation to quantum measurement theory, and establish a logical basis for the difference between simultaneous measurability and simultaneous determinateness.     

Kolmogorov Probability Spaces Describing Accardi Models of Quantum Correlations

In this paper we consider several Kolmogorov type models describing some quantum correlations. The main ideas beyond most of these models comes back to pioneering works of Accardi (see [1, 10, 15] and references therein); because of that we call some of them the Accardi models. Namely we discuss, in our frame, the Kolmogorov type Accardi model of the Aspect version [2] of the Einstein-Podolsky-Rosen (EPR) experiment [3].     

Non-Markovian Quantum Error Deterrence by Dynamical Decoupling in a General Environment

A dynamical decoupling(DD) scheme for the prevention of errors in the non-Markovian (usually corresponding to low temperature, short time, and strong coupling) regimes suitable for qubits constructed out of a multilevel structure is studied. We use the effective spin-boson model (ESBM) introduced recently [K. Shiokawa and B. L. Hu, Phys. Rev. A70, 062106 (2004)] as a low temperature limit of the quantum Brownian oscillator model, where one can obtain exact solutions for a general environment with colored noises. In our decoupling scheme, a train of pairs of strong pulses are used to evolve the interaction Hamiltonian instantaneously. Using this scheme we show that the dynamical decoupling method can suppress 1/f noise with slower and hence more accessible pulses than previously studied, but it still fails to decouple super-Ohmic types of environments.      

General Point Sampling with Adaptive Density and Correlations

Analyzing and generating sampling patterns are fundamental problems for many applications in computer graphics. Ideally, point patterns should conform to the problem at hand with spatially adaptive density and correlations. Although there exist excellent algorithms that can generate point distributions with spatially adaptive density or anisotropy, the pair‐wise correlation model, blue noise being the most common, is assumed to be constant throughout the space. Analogously, by relying on possibly modulated pair‐wise difference vectors, the analysis methods are designed to study only such spatially constant correlations. In this paper, we present the first techniques to analyze and synthesize point patterns with adaptive density and correlations. This provides a comprehensive framework for understanding and utilizing general point sampling. Starting from fundamental measures from stochastic point processes, we propose an analysis framework for general distributions, and a novel synthesis algorithm that can generate point distributions with spatio‐temporally adaptive density and correlations based on a locally stationary point process model. Our techniques also extend to general metric spaces. We illustrate the utility of the new techniques on the analysis and synthesis of real‐world distributions, image reconstruction, spatio‐temporal stippling, and geometry sampling.     

On a Sufficient Condition for Additivity in Quantum Information Theory

In this paper we give a sufficient condition for additivity of the minimum output entropy for a pair of given channels and an analytic verification of this condition for specific quantum channels breaking a closely related multiplicativity property [1, 2]. This yields validity of the additivity conjecture for these channels, a result obtained by a different method in [3]. Our proof relies heavily upon certain concavity properties of the output entropy, which are of independent interest.__________Translated from Problemy Peredachi Informatsii, No. 2, 2005, pp. 9–25.Original Russian Text Copyright © 2005 by Datta, Holevo, Suhov.This work was initiated when the second author was an overseas visiting scholar at St John’s College, Cambridge. Afterwards he was supported by the Russian Scientific School Program, project no. 1758.2003.1. The first and third authors worked in association with the CMI, University of Cambridge - MIT.     

Large Deviations in Quantum Information Theory

We obtain asymptotic estimates for the probabilities of events of special types, which are useful in quantum information theory, especially for identification in noisy channels.     

Some Issues in Quantum Information Theory

Quantum information theory is a new interdisciplinary research field related to quantum mechanics, computer science, information theory, and applied mathematics. It provides completely new paradigms to do information processing tasks by employing the principles of quantum mechanics. In this review, we first survey some of the significant advances in quantum information theory in the last twenty years. We then focus mainly on two special subjects： discrimination of quantum objects and transformations between entanglements. More specifically, we first discuss discrimination of quantum states and quantum apparatus in both global and local settings. Secondly, we present systematical characterizations and equivalence relations of several interesting entanglement transformation phenomena, namely entanglement catalysis, multiple-copy entanglement transformation, and partial entanglement recovery.     

A Quantum Theory of Consciousness

The relationship between quantum collapse and consciousness is reconsidered under the assumption that quantum collapse is an objective dynamical process. We argue that the conscious observer can have a distinct role from the physical measuring device during the process of quantum collapse owing to the intrinsic nature of consciousness; the conscious observer can know whether he is in a definite state or a quantum superposition of definite states, while the physical measuring device cannot “know”. As a result, the consciousness observer can distinguish the definite states and their quantum superposition, while the physical measuring device without consciousness cannot do. This provides a possible quantum physical method to distinguish man and machine. The new result also implies that consciousness has causal efficacies in the physical world when considering the existence of quantum collapse. Accordingly consciousness is not reducible or emergent, but a new fundamental property of matter. This may establish a quantum basis for panpsychism, and make it be a promising solution to the hard problem of consciousness. Furthermore, it is suggested that a unified theory of matter and consciousness includes two parts: one is the psychophysical principle or corresponding principle between conscious content and matter state, and the other is the complete quantum evolution of matter state, which includes the definite nonlinear evolution element introduced by consciousness and relating to conscious content. Lastly, some experimental schemes are presented to test the proposed quantum theory of consciousness.

Mathematical Theory of Duality Quantum Computers

We present a mathematical theory for a new type of quantum computer called a duality quantum computer that has recently been proposed. We discuss the nonunitarity of certain circuits of a duality quantum computer and point out a paradoxical situation that occurs when mixed states are considered. It is shown that a duality quantum computer can measure itself without needing a separate measurement apparatus to determine its final state.      

智能优化算法的量子理论纲要

针对一些智能优化算法缺乏完备数学物理理论基础的现状, 利用优化问题和量子物理在概率意义上的相似性, 建立优化问题的薛定谔方程, 将优化问题转化为以目标函数为约束条件的基态波函数问题, 同时利用波函数定义了算法的能量、隧道效应和熵, 实现了以波函数为中心的优化问题量子模型. 这一纲要利用了量子物理完备的理论框架, 建立起了优化问题与量子理论广泛的内在联系. 从量子物理的角度回答了优化问题解的概率描述, 邻域采样函数的选择, 算法演化的过程设计, 多尺度过程的必要性等问题. 智能优化算法的量子理论纲要可以作为研究与构造算法的理论工具, 其有效性已得到初步验证.     

用量子广义测量控制消相干

本文探讨了把量子广义测量和无消相干子空间 (DFS) 结合起来抑制消相干的潜力. 证实了: 把量子广义子空间投影测量 (QGSPM) 和量子广义分类投影测量 (QGCPM) 与 DFS 算子条件结合起来, 可以有效增强 Markovian 和非 Markovian 量子开放系统抑制消相干的能力. 强调了量子测量可以作为操控量子态的重要手段. 本方法的优点在于可以构造性地设计相干控制哈密顿量.     

Simplification of Additivity Conjecture in Quantum Information Theory

We simplify some conjectures in quantum information theory; the additivity of minimal output entropy, the multiplicativity of maximal output p-norm and the superadditivity of convex closure of output entropy. In this paper, by using some unital extension of quantum channels, we show that proving one of these conjectures for all unital quantum channels would imply that it is also true for all quantum channels.      

A Computational Model for Quantum Measurement

Quantum Information Processing - Is the dynamical evolution of physical systems objectively a manifestation of information processing by the universe? We find that an affirmative answer has...