满层L-收敛空间的局部有界与局部紧性

对满层[L]-收敛空间引入了有界集（紧集）和局部有界（紧）空间的概念,它们可以看作J?ger相应概念的推广。证明了：（1）广义Lowen函子（收敛空间范畴可以通过广义Lowen函子余反射嵌入到满层[L]-收敛空间范畴）保持并且反射有界（紧）性和局部有界（紧）性;（2）局部有界（紧）的满层[L]-收敛空间是满层[L]-收敛空间的余反射子范畴。     

Quantum loop programs

Loop is a powerful program construct in classical computation, but its power is still not exploited fully in quantum computation. The exploitation of such power definitely requires a deep understanding of the mechanism of quantum loop programs. In this paper, we introduce a general scheme of quantum loops and describe its computational process. The function computed by a quantum loop is defined, and a denotational semantics and a weakest precondition semantics of a quantum loop are given. The notions of termination and almost termination are proposed for quantum loops. This paper only consider the case of finite-dimensional state spaces. Necessary and sufficient conditions for termination and almost termination of a general quantum loop on any mixed input state are presented. A quantum loop is said to be (almost) terminating if it (almost) terminates on any input state. We show that a quantum loop is almost terminating if and only if it is uniformly almost terminating. It is observed that a small disturbance either on the unitary transformation in the loop body or on the measurement in the loop guard can make any quantum loop (almost) terminating, provided that some dimension restriction is satisfied. Moreover, a representation of the function computed by a quantum loop is given in terms of finite summations of matrices. To illustrate the notions and results obtained in this paper, two simple classes of quantum loop programs, one qubit quantum loops, and two qubit quantum loops defined by controlled gates, are carefully examined, and to show their expressive power, quantum loops are applied in describing quantum walks.     

On <Emphasis Type="Italic">L</Emphasis>-soft merotopies

The goal of this paper is to focus on the notions of merotopy and also merotopology in the soft universe. First of all, we propose L-soft merotopic (nearness) spaces and L-soft guild. Then, we study binary, contigual, regular merotopic spaces and also relations between them. We show that the category of binary L-soft nearness spaces is bireflective in the category of L-soft nearness spaces. Later, we define L-approach soft merotopological (nearness) spaces by giving several examples. Finally, we define a simpler characterization of L-approach soft grill merotopological space called grill-determined L-approach soft merotopological space. We investigate the categorical structures of these notions such as we prove that the category of grill-determined L-approach soft merotopological spaces is a topological category over the category of L-soft topological spaces. At the end, we define a partial order on the family of all L-approach soft grill merotopologies and show that this family is a completely distributive complete lattice with respect to the defined partial order.     

On effect algebras of fuzzy sets

We introduce the category IE of effect algebras of fuzzy sets and sequentially continuous effect homomorphisms and describe its fundamental properties. We show that IE and the category ID of D-posets of fuzzy sets are isomorphic, hence the constructions and properties of ID related to applications to probability theory are valid for the corresponding effect algebras. We describe basic properties of categorical coproducts in ID and dually of categorical products in the corresponding category MID of measurable spaces. We end with remarks on fuzzy probability notions. Supported by VEGA Grant 1/2002/05.     

Analysis and synthesis of attractive quantum Markovian dynamics

We propose a general framework for investigating a large class of stabilization problems in Markovian quantum systems. Building on the notions of invariant and attractive quantum subsystem, we characterize attractive subspaces by exploring the structure of the invariant sets for the dynamics. Our general analysis results are exploited to assess the ability of open-loop Hamiltonian and output-feedback control strategies to synthesize Markovian generators which stabilize a target subsystem, subspace, or pure state. In particular, we provide an algebraic characterization of the manifold of stabilizable pure states in arbitrary finite-dimensional Markovian systems, that leads to a constructive strategy for designing the relevant controllers. Implications for stabilization of entangled pure states are addressed by example.     

Semantics for a Quantum Programming Language by Operator Algebras

This paper presents a novel semantics for a quantum programming language by operator algebras, which are known to give a formulation for quantum theory that is alternative to the one by Hilbert spaces. We show that the opposite of the category of W*-algebras and normal completely positive subunital maps is an elementary quantum flow chart category in the sense of Selinger. As a consequence, it gives a denotational semantics for Selinger’s first-order functional quantum programming language. The use of operator algebras allows us to accommodate infinite structures and to handle classical and quantum computations in a unified way.     

On the Observer Problem for Discrete-Time Control Systems

This paper studies the construction of observers for nonlinear time-varying discrete-time systems in a general context, where a certain function of the states must be estimated. Appropriate notions of robust complete observability are proposed, under which a constructive proof of existence of an observer is developed. Moreover, a "transitive observer property" is proven, according to which a state observer can be generated as the series connection of two observers. The analysis and the results are developed in general normed linear spaces, to cover both finite-dimensional and infinite-dimensional systems     

Two-dimensional linear algebra

We introduce two-dimensional linear algebra, by which we do not mean two-dimensional vector spaces but rather the systematic replacement in linear algebra of sets by categories. This entails the study of categories that are simultaneously categories of algebras for a monad and categories of coalgebras for comonad on a category such as SymMon_s, the category of small symmetric monoidal categories. We outline relevant notions such as that of pseudo-closed 2-category, symmetric monoidal Lawvere theory, and commutativity of a symmetric monoidal Lawvere theory, and we explain the role of coalgebra, explaining its precedence over algebra in this setting. We outline salient results and perspectives given by the dual approach of algebra and coalgebra, extending to two dimensions the study of linear algebra.     

A topoiogical formulation of linguistic typology

The problem of classifying formal languages with respect to isomorphism is shown to reduce to the equivalence problem for a certain class of triples of topological spaces, and associated pairs of continuous mappings; and this problem can, in turn, be translated into the category of compacta. The computation of topological invariants of languages is illustrated by simple finite examples. An approach to computational applications of these notions to the study of natural and programming languages is indicated, further theoretical problems are posed, and directions for further research are suggested.     

Coupling of quantum angular momenta: an insight into analogic/discrete and local/global models of computation

In the past few years there has been a tumultuous activity aimed at introducing novel conceptual schemes for quantum computing. The approach proposed in (Marzuoli and Rasetti, 2002, 2005a) relies on the (re)coupling theory of SU(2) angular momenta and can be viewed as a generalization to arbitrary values of the spin variables of the usual quantum-circuit model based on ‘qubits’ and Boolean gates. Computational states belong to finite-dimensional Hilbert spaces labelled by both discrete and continuous parameters, and unitary gates may depend on quantum numbers ranging over finite sets of values as well as continuous (angular) variables. Such a framework is an ideal playground to discuss discrete (digital) and analogic computational processes, together with their relationships occurring when a consistent semiclassical limit takes place on discrete quantum gates. When working with purely discrete unitary gates, the simulator is naturally modelled as families of quantum finite states-machines which in turn represent discrete versions of topological quantum computation models. We argue that our model embodies a sort of unifying paradigm for computing inspired by Nature and, even more ambitiously, a universal setting in which suitably encoded quantum symbolic manipulations of combinatorial, topological and algebraic problems might find their ‘natural’ computational reference model.     

L-SLLSC同构L-SSC

对层次满层L-收敛空间引入了强左连续条件,证明了强左连续的层次满层L-收敛空间范畴:可以反射嵌入到层次满层L-收敛空间范畴;恰好可以刻画强满层L-收敛空间范畴。     

Poincaré–Birkhoff–Witt theorem for Leibniz -algebras

We construct the universal enveloping algebra of a Leibniz n-algebra and we prove that the category of modules over this algebra is equivalent to the category of representations.We also give a proof of the Poincaré–Birkhoff–Witt theorem for universal enveloping algebras of finite-dimensional Leibniz n-algebras using Gröbner bases in a free associative algebra.     

Reconstruction of the Fourier expansion of inputs of linear time-varying systems

In this paper we propose a general method to estimate periodic unknown input signals of finite-dimensional linear time-varying systems. We present an infinite-dimensional observer that reconstructs the coefficients of the Fourier decomposition of such systems. Although the overall system is infinite dimensional, convergence of the observer can be proven using a standard Lyapunov approach along with classic mathematical tools such as Cauchy series, Parseval equality, and compact embeddings of Hilbert spaces. Besides its low computational complexity and global convergence, this observer has the advantage of providing a simple asymptotic formula that is useful for tuning finite-dimensional filters. Two illustrative examples are presented.     

Hautus condition on the exact controllability of conservative systems

We consider the exact controllability of a linear conservative system (A,B) associated with Hilbert spaces H and U. We get a necessary and sufficient controllability condition. This condition is related to the Hautus Lemma from the finite-dimensional systems theory. It is an estimate in terms of operators A and B alone.     

Quantum computation with coherent spin states and the close Hadamard problem

We study a model of quantum computation based on the continuously parameterized yet finite-dimensional Hilbert space of a spin system. We explore the computational powers of this model by analyzing a pilot problem we refer to as the close Hadamard problem. We prove that the close Hadamard problem can be solved in the spin system model with arbitrarily small error probability in a constant number of oracle queries. We conclude that this model of quantum computation is suitable for solving certain types of problems. The model is effective for problems where symmetries between the structure of the information associated with the problem and the structure of the unitary operators employed in the quantum algorithm can be exploited.     

Controllability of quantum harmonic oscillators

It is proven in a previous paper that any modal approximation of the one-dimensional quantum harmonic oscillator is controllable. We prove here that, contrary to such finite-dimensional approximations, the original infinite-dimensional system is not controllable: Its controllable part is of dimension 2 and corresponds to the dynamics of the average position. More generally, we prove that, for the quantum harmonic oscillator of any dimension, similar lacks of controllability occur whatever the number of control is: the controllable part still corresponds to the average position dynamics. We show, with the quantum particle in a moving quadratic potential, that some physically interesting motion planning questions can be however solved.     

An application of quantum finite automata to interactive proof systems

Quantum finite automata have been studied intensively since their introduction in late 1990s as a natural model of a quantum computer working with finite-dimensional quantum memory space. This paper seeks their direct application to interactive proof systems in which a mighty quantum prover communicates with a quantum-automaton verifier through a common communication cell. Our quantum interactive proof systems are juxtaposed to Dwork–Stockmeyer's classical interactive proof systems whose verifiers are two-way probabilistic finite automata. We demonstrate strengths and weaknesses of our systems by studying how various restrictions on the behaviors of quantum-automaton verifiers affect the power of quantum interactive proof systems.     

Computer-Aided Construction of Finite Geometric Spaces: Automated Verification of Geometric Constraints

The category of noncommutative geometric spaces is a rather new and wide field in geometry that provides a rich source of hard computer applications. In this contribution we give a short summary of the basic notions of geometric spaces. The so-called parallel map that describes a space will play a fundamental role because, in terms of the parallel map, a geometric space can be represented in such a way that geometric conditions/axioms (which form the structure of a space) are expressible by certain equations. To verify a configuration amounts to showing the solvability of a corresponding equation or a system of equations, respectively. This is a computational aspect that opens the whole field naturally to computer applications by means of automated deduction in geometry, verification of geometric constraints, computer-aided construction of finite geometries. We give motivation why we use specific declarative programming languages for doing all the implementations and computer applications.     

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.     

Symmetries, Group Actions, and Entanglement

We address several problems concerning the geometry of the space of Hermitian operators on a finite-dimensional Hilbert space, in particular the geometry of the space of density states and canonical group actions on it. For quantum composite systems we discuss and give examples of entanglement measures.