Determinisitic Writing and Control of the Dark Exciton Spin using Short Single Optical Pulses

We demonstrate that the quantum dot-confined dark exciton forms a long-lived integer spin solid state qubit which can be deterministically on-demand initiated in a pure state by one optical pulse. Moreover, we show that this qubit can be fully controlled using short optical pulses, which are several orders of magnitude shorter than the life and coherence times of the qubit. Our demonstrations do not require an externally applied magnetic field and they establish that the quantum dot-confined dark exciton forms an excellent solid state matter qubit with some advantages over the half-integer spin qubits such as the confined electron and hole, separately. Since quantum dots are semiconductor nanostructures that allow integration of electronic and photonic components, the dark exciton may have important implications on implementations of quantum technologies consisting of semiconductor qubits.Comment: Added two authors, minor edits to figure captions, expanded discussion of dark exciton eigenstate

A Physicochemical Evaluation of the HQ-1 Core from the Pricetown I, Underground Coal Gasification Test Site

Core samples of coal and rock were obtained from the HQ-1 environmental test well at the Pricetown I, Underground Coal Gasification Test Site. A comprehensive analytical program was performed to characterize the coal samples. The rocks associated with the coals are composed of clay size material containing low amounts of organic matter and hydrocarbon gas relative to the coal seams. The fine grained sediment above and below the coal seams appear to be an effective gas seal. The coals were encountered in two intervals of 1 foot and 6 feet thickness separated by 2 feet of shale. The coals are classified as high volatile A or B bituminous based on vitrinite reflectance, fixed carbon, and calorific value. Coal maceral analysis shows that the coal is heterogeneous in petrographic properties. The vitrinite group is the predominant maceral constituent. Fusinite, semi-fusinite, massive micrinite, and sporinite are present in varying amounts. The distribution of porous fusinite layers within the coal seams may be important in the reverse linkage stage of the gasification process. The coal in the bottom seam contains an average of 45.6 standard cubic feet of free methane per ton of coal. This methane may assist in initiating the gasification process. Thermal Conductivity and Laser Thermal Diffusivity experiments were also performed on selected coal samples as well as on samples of the grout used in the instrumentation wells. While the thermal conductivity values were influenced by the tars and oils generated during the heating of the coal, the laser thermal diffusivity values were obtained at sufficiently low temperatures to minimize the influence of the tars and oils

Classical and Quantum Dynamics in a Random Magnetic Field

Using the supersymmetry approach, we study spectral statistical properties of a two-dimensional quantum particle subject to a non-uniform magnetic field. We focus mainly on the problem of regularisation of the field theory. Our analysis begins with an investigation of the spectral properties of the purely classical evolution operator. We show that, although the kinetic equation is formally time-reversible, density relaxation is controlled by {\em irreversible} classical dynamics. In the case of a weak magnetic field, the effective kinetic operator corresponds to diffusion in the angle space, the diffusion constant being determined by the spectral resolution of the inhomogeneous magnetic field. Applying these results to the quantum problem, we demonstrate that the low-lying modes of the field theory are related to the eigenmodes of the irreversible classical dynamics, and the higher modes are separated from the zero mode by a gap associated with the lowest density relaxation rate. As a consequence, we find that the long-time properties of the system are characterised by universal Wigner-Dyson statistics. For a weak magnetic field, we obtain a description in terms of the quasi one-dimensional non-linear $\sigma$-model.Comment: 16 pages, RevTe

Pressure-Coring of the Gas-bearing Devonian Black Shales

A Christensen model pressure-retaining core barrel is being used in the drilling of two EGSP research wells. This effort supported by two other techniques is designed to evaluate the most effective technique to provide meaningful resource assessments. One well has been successfully drilled and the accumulated samples are currently being evaluated. The second well is currently being drilled

Pion and Sigma Polarizabilities and Radiative Transitions

Fermilab E781 plans measurements of gamma-Sigma and $\gamma$-pion interactions using a 600 GeV beam of Sigmas and pions, and a virtual photon target. Pion polarizabilities and radiative transitions will be measured in this experiment. The former can test a precise prediction of chiral symmetry; the latter for a_1(1260) ----> pi + gamma is important for understanding the polarizability. The experiment also measures polarizabilities and radiative transitions for Sigma hyperons. The polarizabilities can test predictions of baryon chiral perturbation theory. The radiative transitions to the Sigma*(1385) provide a measure of the magnetic moment of the s-quark. Previous experimental and theoretical results for gamma-pi and gamma-Sigma interactions are given. The E781 experiment is described.Comment: 13 pages text (tex), Tel Aviv U. Preprint TAUP 2204-94, uses Springer-Verlag TEX macro package lecproc.cmm (appended at end of tex file, following \byebye), which requires extracting lecproc.cmm and putting this file in your directory in addition to the tex file (mmcd.tex) before tex processing. lecproc.cmm should be used following instructions and guidelines available from Springer-Verlag. Submitted to the Proceedings of Workshop on Chiral Dynamics, Massachusetts Institute of Technology, July 1994, Eds. A. Bernstein, B. Holstein. Replaced Oct. 4 to add TAUP preprint number. Replaced Oct. 12 to correct Pb target thickness from 1.3% interaction to 0.3

Mass Balance Results for Pricetown I Underground Coal Gasification

A mass balance model was applied to the Pricetown I test data. This model gave the values of various parameters such as water influx, percent devolatilization, percent gasification, amount of coal affected, thermal efficiency, etc., for the various phases of the test. Both hourly and daily values of the test data were used. At certain times, there was air loss to the coal seam or air gain from the coal seam as related to the underground reactor. Mass balances are modified accordingly. Realistic pyrolysis temperatures have been chosen for the different phases of the test based on the thermocouple responses. The nitrogen and argon balances gave similar results. The mass balance results showed that approximately 702 tons of coal was affected during the test. Approximately 232 tons of coal was completely gasified. The reverse combustion linkage through the virgin coal seam was dominated by the devolatilization and accounted for approximately 80% devoltilization whereas the same accounted for only 26% devolatilization during the gasification phase. During the enhanced linkage phase, the percent devolatilization ranged between that observed for the RCL and gasification phase. There was net influx of water and amounted to 0.59 barrels per ton of coal affected. The percent energy recovery for the gasification phase was 72% based on gas chromatographic data, and accounting the sensible heat of the gas and the latent heat of the water vapor in the gas

The "forbidden" decays of hybrid mesons to πρ\pi \rho can be large

The observation of $\pi_1(1600) \to \pi \rho$ is shown in the flux-tube model to be compatible with this state being a hybrid meson with branching ratio to this channel $\sim 30$. The $\pi \rho$ widths of other hybrids are related by rather general arguments. These results enable cross sections for photoproduction of hybrids to be predicted.Comment: Replaced with revised version correcting a technical mistake, conclusions remain unchanged. Accepted for publication in PR

On the segmentation and classification of hand radiographs

This research is part of a wider project to build predictive models of bone age using hand radiograph images. We examine ways of finding the outline of a hand from an X-ray as the first stage in segmenting the image into constituent bones. We assess a variety of algorithms including contouring, which has not previously been used in this context. We introduce a novel ensemble algorithm for combining outlines using two voting schemes, a likelihood ratio test and dynamic time warping (DTW). Our goal is to minimize the human intervention required, hence we investigate alternative ways of training a classifier to determine whether an outline is in fact correct or not. We evaluate outlining and classification on a set of 1370 images. We conclude that ensembling with DTW improves performance of all outlining algorithms, that the contouring algorithm used with the DTW ensemble performs the best of those assessed, and that the most effective classifier of hand outlines assessed is a random forest applied to outlines transformed into principal components