Readout of solid-state charge qubits using a single-electron pump

A major difficulty in realizing a solid-state quantum computer is the reliable measurement of the states of the quantum registers. In this paper, we propose an efficient readout scheme making use of the resonant tunneling of a ballistic electron produced by a single electron pump. We treat the measurement interaction in detail by modeling the full spatial configuration, and show that for pumped electrons with suitably chosen energy the transmission coefficient is very sensitive to the qubit state. We further show that by using a short sequence of pumping events, coupled with a simple feedback control procedure, the qubit can be measured with high accuracy.Comment: 5 pages, revtex4, 4 eps figures. v2: published versio

Use of MMG signals for the control of powered orthotic devices: Development of a rectus femoris measurement protocol

Copyright © 2009 Rehabilitation Engineering and Assistive Technology Society (RESNA). This is an Author's Accepted Manuscript of an article published in Assistive Technology, 21(1), 1 - 12, 2009, copyright Taylor & Francis, available online at: http://www.tandfonline.com/10.1080/10400430902945678.A test protocol is defined for the purpose of measuring rectus femoris mechanomyographic (MMG) signals. The protocol is specified in terms of the following: measurement equipment, signal processing requirements, human postural requirements, test rig, sensor placement, sensor dermal fixation, and test procedure. Preliminary tests of the statistical nature of rectus femoris MMG signals were performed, and Gaussianity was evaluated by means of a two-sided Kolmogorov-Smirnov test. For all 100 MMG data sets obtained from the testing of two volunteers, the null hypothesis of Gaussianity was rejected at the 1%, 5%, and 10% significance levels. Most skewness values were found to be greater than 0.0, while all kurtosis values were found to be greater than 3.0. A statistical convergence analysis also performed on the same 100 MMG data sets suggested that 25 MMG acquisitions should prove sufficient to statistically characterize rectus femoris MMG. This conclusion is supported by the qualitative characteristics of the mean rectus femoris MMG power spectral densities obtained using 25 averages

Shot-Noise Signatures of 0.7 Structure and Spin in a Quantum Point Contact

We report simultaneous measurement of shot noise and dc transport in a quantum point contact as a function of source-drain bias, gate voltage, and in-plane magnetic field. Shot noise at zero field exhibits an asymmetry related to the 0.7 structure in conductance. The asymmetry in noise evolves smoothly into the symmetric signature of spin-resolved electron transmission at high field. Comparison to a phenomenological model with density-dependent level splitting yields good quantitative agreement.Comment: related papers at http://marcuslab.harvard.ed

Density dependent spin polarisation in ultra low-disorder quantum wires

There is controversy as to whether a one-dimensional (1D) electron gas can spin polarise in the absence of a magnetic field. Together with a simple model, we present conductance measurements on ultra low-disorder quantum wires supportive of a spin polarisation at B=0. A spin energy gap is indicated by the presence of a feature in the range 0.5 - 0.7 X 2e^2/h in conductance data. Importantly, it appears that the spin gap is not static but a function of the electron density. Data obtained using a bias spectroscopy technique are consistent with the spin gap widening further as the Fermi-level is increased.Comment: 5 Pages 4 Figures email:[email protected]

Correlates, determinants, and effectiveness of childcare educators’ practices and behaviours on preschoolers’ physical activity and eating behaviours: a systematic review protocol

Abstract: Background: Worldwide, approximately 12% of children under the age of 5 are either overweight or obese. As many young children spend 30 h or more per week in childcare centres with childcare educators. Targeting childcare educators as role models may prove an effective strategy for the promotion of healthy eating and physical activity. This manuscript describes the methods to systematically review existing literature relating to how childcare educators influence children’s healthy eating and physical activity behaviours, as well as the links between specific practices and behaviours of childcare educators and children’s healthy lifestyle behaviours. Methods: Relevant peer-reviewed studies will be identified through a computerized literature search in six databases: PubMed, The Cochrane Library, Science Direct, CINAHL, Wiley and SportDiscus. Quantitative studies written in English or French reporting the correlates, predictors or effectiveness of childcare educators’ practices and behaviours on preschoolers’ healthy eating and physical activity behaviours will be included. The quality of retained studies will be assessed using the Quality Assessment Tool for Quantitative Studies. Descriptive summary statistics of study characteristics will be reported as well as the study designs and exposure and outcome measures. Inter-rater agreements for study selection and quality assessments will be reported and unadjusted, and adjusted results will be presented. Reporting of the systematic review will follow the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Discussion: This systematic review will contribute to a better understanding of the potential of childcare educators as role models for young children, as well as the influence (or impact) of their behaviours and intervention on children’s short- and long-term health. It will provide important information that could be used to improve obesity prevention strategies and initiatives, as well as to guide the improvement or implementation of effective healthy eating and physical activity policies in childcare centres. Systematic review registration: PROSPERO (CRD42014012973

Extreme sensitivity of the spin-splitting and 0.7 anomaly to confining potential in one-dimensional nanoelectronic devices

Quantum point contacts (QPCs) have shown promise as nanoscale spin-selective components for spintronic applications and are of fundamental interest in the study of electron many-body effects such as the 0.7 x 2e^2/h anomaly. We report on the dependence of the 1D Lande g-factor g* and 0.7 anomaly on electron density and confinement in QPCs with two different top-gate architectures. We obtain g* values up to 2.8 for the lowest 1D subband, significantly exceeding previous in-plane g-factor values in AlGaAs/GaAs QPCs, and approaching that in InGaAs/InP QPCs. We show that g* is highly sensitive to confinement potential, particularly for the lowest 1D subband. This suggests careful management of the QPC's confinement potential may enable the high g* desirable for spintronic applications without resorting to narrow-gap materials such as InAs or InSb. The 0.7 anomaly and zero-bias peak are also highly sensitive to confining potential, explaining the conflicting density dependencies of the 0.7 anomaly in the literature.Comment: 23 pages, 7 figure

USA and RXTE Observations of a Variable Low-Frequency QPO in XTE J1118+480

The USA experiment on ARGOS and RXTE have exensively observed the X-ray transient XTE J1118+480 during its recent outburst in 2000 April--June. We present detailed monitoring of the evolution of a low frequency QPO which drifts from 0.07 Hz to 0.15 Hz during the outburst. We examine possible correlations of the QPO frequency with the flux and spectral characteristics of the source, and compare this QPO to low frequency QPOs observed in other black hole candidates.Comment: Accepted by ApJ Letters, reference added, minor revisions, 6 page