3,715 research outputs found
Few-electron quantum dots in III-V ternary alloys: role of fluctuations
We study experimentally the electron transport properties of gated quantum
dots formed in InGaAs/InP and InAsP/InP quantum well structures grown by
chemical-beam epitaxy. For the case of the InGaAs quantum well, quantum dots
form directly underneath narrow gate electrodes due to potential fluctuations.
We measure the Coulomb-blockade diamonds in the few-electron regime of a single
quantum dot and observe photon-assisted tunneling peaks under microwave
irradiation. A singlet-triplet transition at high magnetic field and
Coulomb-blockade effects in the quantum Hall regime are also observed. For the
InAsP quantum well, an incidental triple quantum dot forms also due to
potential fluctuations within a single dot layout. Tunable quadruple points are
observed via transport measurements.Comment: 3.3 pages, 3 figures. Added two new subfigures, new references, and
improved the tex
Coherent Transport Through a Quadruple Point in a Few Electron Triple Dot
A few electron double electrostatic lateral quantum dot can be transformed
into a few electron triple quantum dot by applying a different combination of
gate voltages. Quadruple points have been achieved at which all three dots are
simultaneously on resonance. At these special points in the stability diagram
four occupation configurations are possible. Both charge detection and
transport experiments have been performed on this device. In this short paper
we present data and confirm that transport is coherent by observing a Pi phase
shift in magneto-conductance oscillations as one passes through the quadruple
point.Comment: To be published in ICPS Conf. Proceedings 200
Who pays the taxes?
The European Union is legally entitled to the revenue from (1) agricultural and sugar levies, (2) customs duties, (3) a 1 percent rate on each Member States' value added tax base, and (4) a resource on the basis of GNP. Currently, the Union is actively involved in the search for a fifth own revenue source. Therefore, the European Commission (DG XIX) has invited the authors to trace 'who pays the taxes'. As requested, our report gives a general account of methods to investigate impacts of taxation. More specifically, we have estimated the incidence of national tax systems (Germany, the Netherlands, Spain and the United Kingdom), and the incidence of present own resources and prospective new (tax) resources of the European Union. Up till now, such information was not (readily) available.tax incidence in the European Union, prospective new EU tax resources
Enhanced charge detection of spin qubit readout via an intermediate state
We employ an intermediate excited charge state of a lateral quantum dot
device to increase the charge detection contrast during the qubit state readout
procedure, allowing us to increase the visibility of coherent qubit
oscillations. This approach amplifies the coherent oscillation magnitude but
has no effect on the detector noise resulting in an increase in the signal to
noise ratio. In this letter we apply this scheme to demonstrate a significant
enhancement of the fringe contrast of coherent Landau-Zener-Stuckleberg
oscillations between singlet S and triplet T+ two-spin states.Comment: 3 pages, 3 figure
The distribution of effective tax burdens in four EU countries
National policymakers are increasingly aware that their tax policy options are constrained by international tax competition. Important features of national tax systems - notably the tax mix, tax rates and rules which define the tax base - will influence decisions of firms and individuals regarding the location and (re)structuring of economic activities. The aim of the present paper is twofold: Firstly, we detail the tax mix of four member states of the European Union (Germany, The Netherlands, Spain and United Kingdom). Secondly, the paper aims to trace the distribution of the tax burden over rich and poor households in these four countries. Although tax mix and tax rates differ considerably among the four countries included in the study, the distribution of tax burdens proves to be amazingly similar.Distribution of tax burden, European Union; tax mix of Germany, the Netherlands, Spain and United Kingdom
Who pays the taxes?
The European Union is legally entitled to the revenue from (1) agricultural and sugar levies, (2) customs duties, (3) a 1 percent rate on each Member States' value added tax base, and (4) a resource on the basis of GNP. Currently, the Union is actively involved in the search for a fifth own revenue source. Therefore, the European Commission (DG XIX) has invited the authors to trace 'who pays the taxes'. As requested, our report gives a general account of methods to investigate impacts of taxation. More specifically, we have estimated the incidence of national tax systems (Germany, the Netherlands, Spain and the United Kingdom), and the incidence of present own resources and prospective new (tax) resources of the European Union. Up till now, such information was not (readily) available.tax incidence in the European Union, prospective new EU tax resources
Quantum Hall induced currents and the magnetoresistance of a quantum point contact
We report an investigation of quantum Hall induced currents by simultaneous
measurements of their magnetic moment and their effect on the conductance of a
quantum point contact (QPC). Features in the magnetic moment and QPC resistance
are correlated at Landau-level filling factors nu=1, 2 and 4, which
demonstrates the common origin of the effects. Temperature and non-linear sweep
rate dependences are observed to be similar for the two effects. Furthermore,
features in the noise of the induced currents, caused by breakdown of the
quantum Hall effect, are observed to have clear correlations between the two
measurements. In contrast, there is a distinct difference in the way that the
induced currents decay with time when the sweeping field halts at integer
filling factor. We attribute this difference to the fact that, while both
effects are sensitive to the magnitude of the induced current, the QPC
resistance is also sensitive to the proximity of the current to the QPC
split-gate. Although it is clearly demonstrated that induced currents affect
the electrostatics of a QPC, the reverse effect, the QPC influencing the
induced current, was not observed
The distribution of effective tax burdens in four EU countries
National policymakers are increasingly aware that their tax policy options are constrained by international tax competition. Important features of national tax systems - notably the tax mix, tax rates and rules which define the tax base - will influence decisions of firms and individuals regarding the location and (re)structuring of economic activities. The aim of the present paper is twofold: Firstly, we detail the tax mix of four member states of the European Union (Germany, The Netherlands, Spain and United Kingdom). Secondly, the paper aims to trace the distribution of the tax burden over rich and poor households in these four countries. Although tax mix and tax rates differ considerably among the four countries included in the study, the distribution of tax burdens proves to be amazingly similar.Distribution of tax burden, European Union; tax mix of Germany, the Netherlands, Spain and United Kingdom
Reliability training
Discussed here is failure physics, the study of how products, hardware, software, and systems fail and what can be done about it. The intent is to impart useful information, to extend the limits of production capability, and to assist in achieving low cost reliable products. A review of reliability for the years 1940 to 2000 is given. Next, a review of mathematics is given as well as a description of what elements contribute to product failures. Basic reliability theory and the disciplines that allow us to control and eliminate failures are elucidated
Topical cyclodextrin reduces amyloid beta and inflammation improving retinal function in ageing mice
Retinal ageing results in chronic inflammation, extracellular deposition, including that of amyloid beta (Aβ) and declining visual function. In humans this can progress into age-related macular degeneration (AMD), which is without cure. Therapeutic approaches have focused on systemic immunotherapies without clinical resolution. Here, we show using aged mice that 2-Hydroxypropyl-β-cyclodextrin, a sugar molecule given as eye drops over 3 months results in significant reductions in Aβ by 65% and inflammation by 75% in the aged mouse retina. It also elevates retinal pigment epithelium specific protein 65 (RPE65), a key molecule in the visual cycle, in aged retina. These changes are accompanied by a significant improvement in retinal function measured physiologically. 2-Hydroxypropyl-β-cyclodextrin is as effective in reducing Aβ and inflammation in the complement factor H knockout (Cfh(-/-)) mouse that shows advanced ageing and has been proposed as an AMD model. β-cyclodextrin is economic, safe and may provide an efficient route to reducing the impact of retinal ageing
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