Gapped Two-Body Hamiltonian for Continuous-Variable Quantum Computation

We introduce a family of Hamiltonian systems for measurement-based quantum computation with continuous variables. The Hamiltonians (i) are quadratic, and therefore two body, (ii) are of short range, (iii) are frustration-free, and (iv) possess a constant energy gap proportional to the squared inverse of the squeezing. Their ground states are the celebrated Gaussian graph states, which are universal resources for quantum computation in the limit of infinite squeezing. These Hamiltonians constitute the basic ingredient for the adiabatic preparation of graph states and thus open new venues for the physical realization of continuous-variable quantum computing beyond the standard optical approaches. We characterize the correlations in these systems at thermal equilibrium. In particular, we prove that the correlations across any multipartition are contained exactly in its boundary, automatically yielding a correlation area law. © 2011 American Physical Society.

Where are all the men? The marginalization of men in social scientific research on infertility

There is a wealth of research exploring the psychological consequences of infertility and assisted reproduction technology: a substantial body of sociological and anthropological work on ‘reproductive disruptions’ of many kinds and a small but growing literature on patient perspectives of the quality of care in assisted reproduction. In all these fields, research studies are far more likely to be focused on the understandings and experiences of women than those of men. This paper discusses reasons for the relative exclusion of men in what has been called the ‘psycho-social’ literature on infertility, comments on research on men from psychological and social perspectives and recent work on the quality of patient care, and makes suggestions for a reframing of the research agenda on men and assisted reproduction. Further research is needed in all areas, including: perceptions of infertility and infertility treatment seeking; experiences of treatment; information and support needs; decisions to end treatment; fatherhood post assisted conception; and the motivation and experiences of sperm donors and men who seek fatherhood through surrogacy or co-parenting. This paper argues for multimethod, interdisciplinary research that includes broader populations of men which can contribute to improved clinical practice and support for users of assisted reproduction treatment

COMPUTATION OF SYNTHETIC SPECTRA FROM SIMULATIONS OF RELATIVISTIC SHOCKS

Particle-in-cell (PIC) simulations of relativistic shocks are in principle capable of predicting the spectra of photons that are radiated incoherently by the accelerated particles. The most direct method evaluates the spectrum using the fields given by the Lienard-Wiechart potentials. However, for relativistic particles this procedure is computationally expensive. Here we present an alternative method that uses the concept of the photon formation length. The algorithm is suitable for evaluating spectra both from particles moving in a specific realization of a turbulent electromagnetic field or from trajectories given as a finite, discrete time series by a PIC simulation. The main advantage of the method is that it identifies the intrinsic spectral features and filters out those that are artifacts of the limited time resolution and finite duration of input trajectories.

A Wavelet Approach to the Selective Computation of Eigenvalues for Small Signal Stability Analysis

This paper proposes a method to assess the small signal stability of a power system network by selective determination of the modal eigenvalues. This uses an accelerating polynomial transform, designed using approximate eigenvalues
obtained from a wavelet approximation. Application to the IEEE 14 bus network model produced computational savings of 20%,over the QR algorithm.

A Wavelet Approach to the Selective Computation of Domninant Eigenvalues

This paper introduces an algorithm that calculates the dominant eigenvalues (in terms of system stability) of a linear model and neglects the exact computation of the non-dominant eigenvalues. The method estimates all of the eigenvalues using wavelet based compression techniques. These estimates are used to find a suitable invariant subspace such that projection by this subspace will provide one containing the eigenvalues of interest. The proposed algorithm is exemplified by application to a power system model.

Derivation of scientific software from mathematical specifications

Often the modification and enhancement of large scientific software systems are severely hampered because many components of the system are written in an implementation dependent fashion, they are inadequately documented, and their functionalities are not precisely known. In this paper we consider how mathematics may be employed to alleviate some of these problems. In particular, we illustrate how the formal specification notation VDM-SL is being used to specify precisely abstract data types for use in the development of scientific software.