Characterization of Combinatorially Independent Permutation Separability Criteria

The so-called permutation separability criteria are simple operational conditions that are necessary for separability of mixed states of multipartite systems: (1) permute the indices of the density matrix and (2) check if the trace norm of at least one of the resulting operators is greater than one. If it is greater than one then the state is necessarily entangled. A shortcoming of the permutation separability criteria is that many permutations give rise to equivalent separability criteria. Therefore, we introduce a necessary condition for two permutations to yield independent criteria called combinatorial independence. This condition basically means that the map corresponding to one permutation cannot be obtained by concatenating the map corresponding to the second permutation with a norm-preserving map. We characterize completely combina-torially independent criteria, and determine simple permutations that represent all independent criteria. The representatives can be visualized by means of a simple graphical notation. They are composed of three basic operations: partial transpose, and two types of so-called reshufflings. In particular, for a four-partite system all criteria except one are composed of partial transpose and only one type of reshuffling; the exceptional one requires the second type of reshuffling. Furthermore, we show how to obtain efficiently a simple representative for every permutation. This method allows to check easily if two permutations are Combinatorially equivalent or not.     

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.     

Relations Between Quantum Maps and Quantum States

The relation between completely positive maps and compound states is investigated in terms of the notion of quantum conditional probability.     

On Duality between Quantum Maps and Quantum States

We investigate the space of quantum operations, as well as the larger space of maps which are positive, but not completely positive. A constructive criterion for decomposability is presented. A certain class of unistochastic operations, determined by unitary matrices of extended dimensionality, is defined and analyzed. Using the concept of the dynamical matrix and the Jamiokowski isomorphism we explore the relation between the set of quantum operations (dynamics) and the set of density matrices acting on an extended Hilbert space (kinematics). An analogous relation is established between the classical maps and an extended space of the discrete probability distributions.     

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     

Classifying Problems on Linear Congruences and Abelian Permutation Groups Using Logspace Counting Classes

In this paper we classify the complexity of several problems based on Abelian permutation groups and linear congruences using logspace counting classes. The problems we consider were defined by McKenzie & Cook (1987).     

Stability Criteria of Linear Neutral Systems With Multiple Delays

In the present note, stability of linear neutral systems with multiple delays is investigated. By principle of the argument, stability criteria are derived which are necessary and sufficient for asymptotic stability of the neutral systems. The stability criteria need only to evaluate the characteristic function and the argument on the boundary of a certain rectangular region. Several numerical examples are given to illustrate the results     

Non-Decomposable Quantum Dynamical Semigroups and Bound Entangled States

We use open quantum system techniques to construct one-parameter semigroups of positive maps and apply them to study the entanglement properties of a class of 16-dimensional density matrices, representing states of a 4 × 4 bipartite system.Presented at the International Conference “Entanglement, Information & Noise”, Krzyżowa, Poland, June 14–20, 2004.     

Controllability and Universal Three-qubit Quantum Computation with Trapped Electron States

We show how to control and perform universal three-qubit quantum computation with trapped electron quantum states. The three qubits are the electron spin, and the first two quantum states of the cyclotron and axial harmonic oscillators. We explicitly show how universal three-qubit gates can be performed. As an example of a quantum algorithm, we outline the implementation of the three-qubit Deutsch-Jozsa algorithm in this system.      

Test of Inseparability Criteria for Squeezed Number States of the Radiation Field

We investigate the efficiency of inseparability criteria in detecting the entanglement properties of two-mode non-Gaussian states of the electromagnetic field. We focus our study on the relevant class of two-mode squeezed number states. These states combine the entangling capability of two-mode squeezers with the non-Gaussian character (nonclassicality) of number states. They allow for some exact analytical treatments, and include as a particular case the two-mode Gaussian squeezed vacuum. We show that the generalized PPT criterion recently proposed by Shchukin and Vogel, based on higher order statistical moments, is very efficient in detecting the entanglement for this class of non-Gaussian states.     

基于半定规划的量子状态最优无错区分

对于一般的量子状态最优无错区分问题.很难得到最优量子测量的解析形式.因此,有必要寻求有效实用的数值方法.基于半定规划理论,证明了无错状态区分的最优量子测肇的设计问题可以转化为标准的半定规划问题,以及能直接应用半定规划的最优性条件,从而更简明地推导了.一组无错状态区分的最优性条件;通过求解标准的半定规划问题.可在多项式时间内直接得到最优量子测量的数值解以及成功区分状态的最大概率值.实例仿真表明,方法易于计算机实现,能有效地设计出无错状态区分的最优量子测量算子.     

The Two-Point Correlation Function: A Measure of Interclass Separability

In this paper we introduce the two-point correlation function as a measure of interclass separability. We present a theoretical study of this statistic in a general M-dimensional feature space and propose a fast algorithm for the efficient computation of it. We test the algorithm and illustrate the properties of the statistic using test data in 1D and 2D feature spaces and discuss the boundary effects of the feature space. We also present a discussion of the limitations of the proposed statistic and apply it to the assessment of inter-class separability in a texture segmentation context.     

On the Modal Logic of the Non-orthogonality Relation Between Quantum States

It is well known that the non-orthogonality relation between the (pure) states of a quantum system is reflexive and symmetric, and the modal logic \(\mathbf {KTB}\) is sound and complete with respect to the class of sets each equipped with a reflexive and symmetric binary relation. In this paper, we consider two properties of the non-orthogonality relation: Separation and Superposition. We find sound and complete modal axiomatizations for the classes of sets each equipped with a reflexive and symmetric relation that satisfies each one of these two properties and both, respectively. We also show that the modal logics involved are decidable.