Retrodiction as a tool for micromaser field measurements

We use retrodictive quantum theory to describe cavity field measurements by successive atomic detections in the micromaser. We calculate the state of the micromaser cavity field prior to detection of sequences of atoms in either the excited or ground state, for atoms that are initially prepared in the excited state. This provides the POM elements, which describe such sequences of measurements.Comment: 20 pages, 4(8) figure

Reviewing and extending the five-user assumption: A grounded procedure for interaction evaluation

" © ACM, 2013. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in ACM Transactions on Computer-Human Interaction (TOCHI), {VOL 20, ISS 5, (November 2013)} http://doi.acm.org/10.1145/2506210 "The debate concerning how many participants represents a sufficient number for interaction testing is well-established and long-running, with prominent contributions arguing that five users provide a good benchmark when seeking to discover interaction problems. We argue that adoption of five users in this context is often done with little understanding of the basis for, or implications of, the decision. We present an analysis of relevant research to clarify the meaning of the five-user assumption and to examine the way in which the original research that suggested it has been applied. This includes its blind adoption and application in some studies, and complaints about its inadequacies in others. We argue that the five-user assumption is often misunderstood, not only in the field of Human-Computer Interaction, but also in fields such as medical device design, or in business and information applications. The analysis that we present allows us to define a systematic approach for monitoring the sample discovery likelihood, in formative and summative evaluations, and for gathering information in order to make critical decisions during the interaction testing, while respecting the aim of the evaluation and allotted budget. This approach – which we call the ‘Grounded Procedure’ – is introduced and its value argued.The MATCH programme (EPSRC Grants: EP/F063822/1 EP/G012393/1

Violation of Leggett inequalities in orbital angular momentum subspaces

We report an experimental test of Leggett's non-local hidden variable theory in an orbital angular momentum (OAM) state space of light. We show that the correlations we observe are in conflict with Leggett's model, thus excluding a particular class of non-local hidden variable theories for the first time in a non-polarization state space. It is known that the violation of the Leggett inequality becomes stronger as more detection settings are used. The required measurements become feasible in an OAM subspace, and we demonstrate this by testing the inequality using three and four settings. We observe excellent agreement with quantum predictions and a violation of five and six standard deviations, respectively, compared to Leggett's non-local hidden variable theory

On the Quantum Phase Operator for Coherent States

In papers by Lynch [Phys. Rev. A41, 2841 (1990)] and Gerry and Urbanski [Phys. Rev. A42, 662 (1990)] it has been argued that the phase-fluctuation laser experiments of Gerhardt, B\"uchler and Lifkin [Phys. Lett. 49A, 119 (1974)] are in good agreement with the variance of the Pegg-Barnett phase operator for a coherent state, even for a small number of photons. We argue that this is not conclusive. In fact, we show that the variance of the phase in fact depends on the relative phase between the phase of the coherent state and the off-set phase $\phi_0$ of the Pegg-Barnett phase operator. This off-set phase is replaced with the phase of a reference beam in an actual experiment and we show that several choices of such a relative phase can be fitted to the experimental data. We also discuss the Noh, Foug\`{e}res and Mandel [Phys.Rev. A46, 2840 (1992)] relative phase experiment in terms of the Pegg-Barnett phase taking post-selection conditions into account.Comment: 8 pages, 8 figures. Typographical errors and misprints have been corrected. The outline of the paper has also been changed. Physica Scripta (in press

Generation of graph-state streams

We propose a protocol to generate a stream of mobile qubits in a graph state through a single stationary parent qubit and discuss two types of its physical implementation, namely, the generation of photonic graph states through an atom-like qubit and those of flying atoms through a cavity-mode photonic qubit. The generated graph states fall into an important class that can hugely reduce the resource requirement of fault-tolerant linear optics quantum computation, which was previously known to be far from realistic. In regard to the flying atoms, we also propose a heralded generation scheme, which allows for high-fidelity graph states even under the photon loss.Comment: Accepted for publication at PRA Rapid Communication

Field guide for didymo DNA sample collection

This protocol is designed for work in two-person teams for both safety and to maximise sample integrity

The Enlightenment and religion: The myths of modernity

The Enlightenment and religion: The myths of modernity offers a critical survey of religious change and its causes in eighteenth-century Europe, and constitutes a radical challenge to the accepted views in traditional Enlightenment studies. Focusing on Enlightenment Italy, France and England, it illustrates how the canonical view of eighteenth-century religious change has in reality been constructed upon scant evidence and assumption, in particular the idea that the thought of the enlightened led to modernity. For despite a lack of evidence, one of the fundamental assumptions of Enlightenment studies has been the assertion that there was a vibrant deist movement that formed the 'intellectual solvent' of the eighteenth century. The central claim of this book is that the immense ideological appeal of the traditional birth-of-modernity myth has meant that the actual lack of deists has been glossed over, and a quite misleading historical view has become entrenched. As a consequence more traditional forces for religious change have been given little or no attention. The book also raises hitherto neglected but fundamental methodological issues relating to the study of the eighteenth century and the ability of 'interested' contemporaries to mislead posterity. Given the current pervasive topicality of notions of modernity and postmodernity in academia, this book advances a very important discussion indeed, and will be essential reading for all students studying the period

Structural characterisation of semi-insulating LEC gallium arsenide

Double crystal x-ray topography using a synchrotron radiation source has been used to measure the lattice distortions present in 50mm diameter samples of (001) semi-insulating LEG gallium arsenide. Lattice strains and tilts have been mapped in In-doped and undoped samples as well as annealed and unannealed samples taken from the seed and tail ends of boules. The properties of the x-ray source which are necessary for these measurements are discussed and it is concluded that a synchrotron source is the only practical choice. Lattice strains of 90ppm and tilts greater than 100 arc seconds were measured in In-doped material both of which appear to be due to a combination of In concentration variations and the inhomogeneous dislocation distribution. Undoped samples were found to be more uniform with lattice strains of typically +20ppm towards the samples edges where the dislocation density is largest. The lattice tilt distribution in seed and undoped samples invariably exhibited a four-fold symmetry which was enhanced by the presence of lineage features lying along the directions. Tail end samples were generally less uniform in lattice strain and showed a lower symmetry in their lattice tilts. These results are discussed in the light of current ideas concerning the origin of variations in lattice strain and EL2 concentration. An x-ray diffraction method involving integrated intensity measurements of the quasi-forbidden 200 reflection, which is highly stoichiometry sensitive, is investigated. The results, however, show no conclusive stoichiometry variations but do highlight important experimental conditions which must be satisfied if such measurements are to be meaningful. The images of dislocations in double crystal x-ray topographs are investigated and compared with theoretical simulations in order to assess the effects of point defect environment on the dislocation strain field. The results suggest that the EL2-dislocation interaction is not significantly strain driven