Using continuous measurement to protect a universal set of quantum gates within a perturbed decoherence-free subspace

We consider a universal set of quantum gates encoded within a perturbed decoherence-free subspace of four physical qubits. Using second-order perturbation theory and a measuring device modelled by an infinite set of harmonic oscillators, simply coupled to the system, we show that continuous observation of the coupling agent induces inhibition of the decoherence due to spurious perturbations. We thus advance the idea of protecting or even creating a decoherence-free subspace for processing quantum information.

Pore size distribution analysis of activated carbons: Application of density functional theory using nongraphitized carbon black as a reference system

The application of nonlocal density functional theory (NLDFT) to determine pore size distribution (PSD) of activated carbons using a nongraphitized carbon black, instead of graphitized thermal carbon black, as a reference system is explored. We show that in this case nitrogen and argon adsorption isotherms in activated carbons are precisely correlated by the theory, and such an excellent correlation would never be possible if the pore wall surface was assumed to be identical to that of graphitized carbon black. It suggests that pore wall surfaces of activated carbon are closer to that of amorphous solids because of defects of crystalline lattice, finite pore length, and the presence of active centers.. etc. Application of the NLDFT adapted to amorphous solids resulted in quantitative description of N-2 and Ar adsorption isotherms on nongraphitized carbon black BP280 at their respective boiling points. In the present paper we determined solid-fluid potentials from experimental adsorption isotherms on nongraphitized carbon black and subsequently used those potentials to model adsorption in slit pores and generate a corresponding set of local isotherms, which we used to determine the PSD functions of different activated carbons. (c) 2005 Elsevier Ltd. All rights reserved.

Random vibration of the functionally graded laminates in thermal environments

This work deals with the random free vibration of functionally graded laminates with general boundary conditions and subjected to a temperature change, taking into account the randomness in a number of independent input variables such as Young's modulus, Poisson's ratio and thermal expansion coefficient of each constituent material. Based on third-order shear deformation theory, the mixed-type formulation and a semi-analytical approach are employed to derive the standard eigenvalue problem in terms of deflection, mid-plane rotations and stress function. A mean-centered first-order perturbation technique is adopted to obtain the second-order statistics of vibration frequencies. A detailed parametric study is conducted, and extensive numerical results are presented in both tabular and graphical forms for laminated plates that contain functionally graded material which is made of aluminum and zirconia, showing the effects of scattering in thermo-clastic material constants, temperature change, edge support condition, side-to-thickness ratio, and plate aspect ratio on the stochastic characteristics of natural frequencies. (c) 2005 Elsevier B.V. All rights reserved.

Telling the story of theory of mind: Deaf and hearing children's narratives and mental state understanding

Theory of mind (ToM) was examined in late-signing deaf children in two studies by using standard tests and measures of spontaneous talk about inner states of perception, affect and cognition during storytelling. In Study 1, there were 21 deaf children aged 6 to 11 years and 13 typical-hearing children matched with the deaf by chronological age. In Study 2, there were 17 deaf children aged 6 to 12 years and 17 typical-hearing preschoolers aged 4 to 5 years who were matched with the deaf by ToM test performance. In addition to replicating the consistently reported finding of poor performance on standard false belief tests by late-signing deaf children, significant correlations emerged in both studies between deaf children's ToM test scores and their spontaneous narrative talk about imaginative cognition (e.g. 'pretend'). In Study 2, with a new set of purpose-built pictures that evoked richer and more complex mentalistic narration than the published picture book of Study 1, results of multiple regression analyses showed that children's narrative talk about imaginative cognition was uniquely important, over and above hearing status and talking of other kinds of mental states, in predicting ToM scores. The same was true of children's elaborated narrative talk using utterances that either spelt out thoughts, explained inner states or introduced contrastives. In addition, results of a Guttman scalograrn analysis in Study 2 suggested a consistent sequence in narrative and standard test performance by deaf and hearing children that went from (1) narrative mention of visible (affective or perceptual) mental states only, along with FB failure, to (2) narrative mention of cognitive states along with (1), to (3) elaborated narrative talk about inner states along with (2), and finally to (4) simple and elaborated narrative talk about affective/perceptual and cognitive states along with FIB test success. Possible explanations for this performance ordering, as well as for the observed correlations in both studies between ToM test scores and narrative variables, were considered.

The role of self-efficacy in predicting rule-following behaviors in shelters for homeless youth: A test of the theory of planned behavior

Through a prospective study of 70 youths staying at homeless-youth shelters, the authors tested the utility of I. Ajzen's (1991) theory of planned behavior (TPB), by comparing the constructs of self-efficacy with perceived behavioral control (PBC), in predicting people's rule-following behavior during shelter stays. They performed the 1st wave of data collection through a questionnaire assessing the standard TPB components of attitudes, subjective norms, PBC, and behavioral intentions in relation to following the set rules at youth shelters. Further, they distinguished between items assessing PBC (or perceived control) and those reflecting self-efficacy (or perceived difficulty). At the completion of each youth's stay at the shelter, shelter staff rated the rule adherence for that participant. Regression analyses revealed some support for the TPB in that subjective norm was a significant predictor of intentions. However, self-efficacy emerged as the strongest predictor of intentions and was the only significant predictor of rule-following behavior. Thus, the results of the present study indicate the possibility that self-efficacy is integral to predicting rule adherence within this context and reaffirm the importance of incorporating notions of people's perceived ease or difficulty in performing actions in models of attitude-behavior prediction.

Bridging the divide between theory and practice. Experiential learning approaches for tourism and hospitality education

Experiential learning approaches such as role-play have been found to be valuable methods of bridging the divide between academic knowledge and practical skills, a problem often cited in tourism and hospitality management education. Such approaches have been found to contribute towards deeper learning by enhancing students' interest, motivation, participation, knowledge and skill development. This paper reports on the implementation of an experiential learning approach designed to encourage and facilitate deeper learning approaches, with the contributing aims of providing students with a more interesting learning experience and a broader set of skills for future employment.

A scalarization technique for computing the power and exponential moments of gaussian random matrices

We consider the problems of computing the power and exponential moments EXs and EetX of square Gaussian random matrices X=A+BWC for positive integer s and real t, where W is a standard normal random vector and A, B, C are appropriately dimensioned constant matrices. We solve the problems by a matrix product scalarization technique and interpret the solutions in system-theoretic terms. The results of the paper are applicable to Bayesian prediction in multivariate autoregressive time series and mean-reverting diffusion processes.

Advanced mean field methods:theory and practice

A major problem in modern probabilistic modeling is the huge computational complexity involved in typical calculations with multivariate probability distributions when the number of random variables is large. Because exact computations are infeasible in such cases and Monte Carlo sampling techniques may reach their limits, there is a need for methods that allow for efficient approximate computations. One of the simplest approximations is based on the mean field method, which has a long history in statistical physics. The method is widely used, particularly in the growing field of graphical models. Researchers from disciplines such as statistical physics, computer science, and mathematical statistics are studying ways to improve this and related methods and are exploring novel application areas. Leading approaches include the variational approach, which goes beyond factorizable distributions to achieve systematic improvements; the TAP (Thouless-Anderson-Palmer) approach, which incorporates correlations by including effective reaction terms in the mean field theory; and the more general methods of graphical models. Bringing together ideas and techniques from these diverse disciplines, this book covers the theoretical foundations of advanced mean field methods, explores the relation between the different approaches, examines the quality of the approximation obtained, and demonstrates their application to various areas of probabilistic modeling.

The theory of on-line learning: a statistical physics approach

In this paper we review recent theoretical approaches for analysing the dynamics of on-line learning in multilayer neural networks using methods adopted from statistical physics. The analysis is based on monitoring a set of macroscopic variables from which the generalisation error can be calculated. A closed set of dynamical equations for the macroscopic variables is derived analytically and solved numerically. The theoretical framework is then employed for defining optimal learning parameters and for analysing the incorporation of second order information into the learning process using natural gradient descent and matrix-momentum based methods. We will also briefly explain an extension of the original framework for analysing the case where training examples are sampled with repetition.

Statistical mechanics of typical set decoding

The performance of "typical set (pairs) decoding" for ensembles of Gallager's linear code is investigated using statistical physics. In this decoding method, errors occur, either when the information transmission is corrupted by atypical noise, or when multiple typical sequences satisfy the parity check equation as provided by the received corrupted codeword. We show that the average error rate for the second type of error over a given code ensemble can be accurately evaluated using the replica method, including the sensitivity to message length. Our approach generally improves the existing analysis known in the information theory community, which was recently reintroduced in IEEE Trans. Inf. Theory 45, 399 (1999), and is believed to be the most accurate to date. © 2002 The American Physical Society.

Nickel(II) complexes of whole set of the simple ethylenediaminetetracarboxylate ligands:DFT study of complexes invoking molecular orbital and configurational analysis

The whole set of the nickel(II) complexes with no derivatized edta-type hexadentate ligands has been investigated from their structural and electronic properties. Two more complexes have been prepared in order to complete the whole set: trans(O5)-[Ni(ED3AP)]2- and trans(O5O6)-[Ni(EDA3P)]2- complexes. trans(O5) geometry has been verified crystallographically and trans(O5O6) geometry of the second complex has been predicted by the DFT theory and spectral analysis. Mutual dependance has been established between: the number of the five-membered carboxylate rings, octahedral/tetrahedral deviation of metal-ligand/nitrogen-neighbour-atom angles and charge-transfer energies (CTE) calculated by the Morokuma’s energetic decomposition analysis; energy of the absorption bands and HOMO–LUMO gap.

What does endogenous growth theory tell about regional economies? Empirics of R&D worker-based productivity growth

What does endogenous growth theory tell about regional economies? Empirics of R&D worker-based productivity growth, Regional Studies. Endogenous growth theory emerged in the 1990s as ‘new growth theory’ accounting for technical progress in the growth process. This paper examines the role of research and development (R&D) workers underlying the Romer model (1990) and its subsequent modifications, and compares it with a model based on the accumulation of human capital engaged in R&D. Cross-section estimates of the models against productivity growth of European regions in the 1990s suggest that each R&D worker has a unique set of knowledge while his/her contributions are enhanced by knowledge sharing within a region as well as spillovers from other regions in proximity.

On the opportunism-independent theory of the firm

Previous developments in the opportunism-independent theory of the firm are either restricted to special cases or are derived from the capabilities or resource-based perspective. However, a more general opportunism-independent approach can be developed, based on the work of Demsetz and Coase, which is nevertheless contractual in nature. This depends on 'direction', that is, deriving economic value by permitting one set of actors to direct the activities of another, and of non-human factors of production. Direction helps to explain not only firm boundaries and organisation, but also the existence of firms, without appealing to opportunism or moral hazard. The paper also considers the extent to which it is meaningful to speak of 'contractual' theories in the absence of opportunism, and whether this analysis can be extended beyond the employment contract to encompass ownership of assets by the firm. © The Author 2005. Published by Oxford University Press on behalf of the Cambridge Political Economy Society. All rights reserved.

Emulation of random output simulators

Computer models, or simulators, are widely used in a range of scientific fields to aid understanding of the processes involved and make predictions. Such simulators are often computationally demanding and are thus not amenable to statistical analysis. Emulators provide a statistical approximation, or surrogate, for the simulators accounting for the additional approximation uncertainty. This thesis develops a novel sequential screening method to reduce the set of simulator variables considered during emulation. This screening method is shown to require fewer simulator evaluations than existing approaches. Utilising the lower dimensional active variable set simplifies subsequent emulation analysis. For random output, or stochastic, simulators the output dispersion, and thus variance, is typically a function of the inputs. This work extends the emulator framework to account for such heteroscedasticity by constructing two new heteroscedastic Gaussian process representations and proposes an experimental design technique to optimally learn the model parameters. The design criterion is an extension of Fisher information to heteroscedastic variance models. Replicated observations are efficiently handled in both the design and model inference stages. Through a series of simulation experiments on both synthetic and real world simulators, the emulators inferred on optimal designs with replicated observations are shown to outperform equivalent models inferred on space-filling replicate-free designs in terms of both model parameter uncertainty and predictive variance.

The theory-practice divide:thoughts from the Editors and Senior Advisory Board of EJM

Purpose – The purpose of this editorial is to bring together thoughts and opinions from the Editors and Senior Advisory Board of EJM regarding the nature of the long-debated “theory-practice divide” in marketing scholarship. Design/methodology/approach – The authors synthesise diverse opinions from senior academics in order both to inspire further debate in marketing scholarship, and to draw some important conclusions for marketing academia as a whole. Findings – The authors propose that, for marketing scholarship to mature and progress, room must be found for those who wish to focus both on practical and on pure marketing scholarship. Career advancement from both routes is vital. Research limitations/implications – The topic of the theory-practice gap is complex. Many diverse opinions are cited and, due to space constraints, the coverage of many issues is necessarily brief. Practical implications – Scholars should find the thoughts contained in the paper of significant interest. Originality/value – The paper appears to be the first to bring together such a set of diverse opinions on the subject, and to try to draw some overall pragmatic conclusions, while still recognising the multiplicity of valid thought in the area.