The quadrupole resonator: Construction, RF System Field Calculations and First Applications

The quadrupole resonator allows measurement of the RF properties of superconducting (sc) films deposited on disk-shaped metallic substrates. We describe the construction of the apparatus, the brazing and electron-beam welding procedures, the arrangements for compensating mechanical tolerances of samples and for assuring reproducible sample illumination. We explain the special features of the RF sy stem and give the results of field calculations with a 3D cavity code. Finally we present first measurements of Nb on Cu film samples and compare them with calibrations done with a bulk Nb sample

Optimal classical-communication-assisted local model of n-qubit Greenberger-Horne-Zeilinger correlations

We present a model, motivated by the criterion of reality put forward by Einstein, Podolsky, and Rosen and supplemented by classical communication, which correctly reproduces the quantum-mechanical predictions for measurements of all products of Pauli operators on an n-qubit GHZ state (or ``cat state''). The n-2 bits employed by our model are shown to be optimal for the allowed set of measurements, demonstrating that the required communication overhead scales linearly with n. We formulate a connection between the generation of the local values utilized by our model and the stabilizer formalism, which leads us to conjecture that a generalization of this method will shed light on the content of the Gottesman-Knill theorem.Comment: New version - expanded and revised to address referee comment

Thickness-dependent thermal properties of amorphous insulating thin films measured by photoreflectance microscopy

In this work, we report on the measurement of the thermal conductivity of thin insulating films of SiO2 obtained by thermal oxidation, and Al2O3 grown by atomic layer deposition (ALD), both on Si wafers. We used photoreflectance microscopy to determine the thermal properties of the films as a function of thickness in the 2 nm to 1000 nm range. The effective thermal conductivity of the Al2O3 layer is shown to decrease with thickness down to 70% for the thinnest layers. The data were analyzed upon considering that the change in the effective thermal conductivity corresponds to an intrinsic thermal conductivity associated to an additional interfacial thermal resistance. The intrinsic conductivity and interfacial thermal resistance of SiO2 were found to be equal to 0.95 W/m·K and 5.1 × 10− 9 m2K/W respectively; those of Al2O3 were found to be 1.56 W/m·K and 4.3 × 10− 9 m2K/W

Implementing an analog speedometer in STISIM Drive using Parallax BSTAMP microcontroller

In a non-instrumental cab, STISIM Drive software normally projects the speed of the vehicle through a dashboard presented on the simulation screen. The simulated dashboard can be displayed with several graphical options. In all cases, there is a loss of information arising from the road. A solution is to integrate the speedometer into a dashboard and to disable the simulated projection. This solution increases the virtual immersion of the driver and presents speed in a more realistic way. We are proposing a simple solution based on Parallax Inc. Basic Stramp microcontroller. In addition to its low cost and simplicity, this solution allows integration of other technical elements of the driving experience (e.g., activation of turn signals, horn, etc.)

Entanglement of Dirac fields in non-inertial frames

We analyze the entanglement between two modes of a free Dirac field as seen by two relatively accelerated parties. The entanglement is degraded by the Unruh effect and asymptotically reaches a non-vanishing minimum value in the infinite acceleration limit. This means that the state always remains entangled to a degree and can be used in quantum information tasks, such as teleportation, between parties in relative uniform acceleration. We analyze our results from the point of view afforded by the phenomenon of entanglement sharing and in terms of recent results in the area of multi-qubit complementarity.Comment: 15 pages, with 8 figures (Mar 2006); accepted to Physical Review A, July 2006 - slightly revise

Response to ‘A well-established fact: Rapid mineralization of organic inputs is an important factor for soil carbon sequestration’ by Angers et al.

Letter to the edito

Feasibility study of a 2 GeV superconducting H−H^{-} linac as injector for the CERN PS

This preliminary feasibility study is based on the availability of the CERN LEP2 superconducting RF system after LEP de-commissioning. The option that is explored is to use this system as part of a high energy H- linac injecting at 2 GeV into the CERN PS, with the aim of reliably providing at its output twice the presently foreseen transverse beam brightness at the ultimate intensity envisaged for LHC. This requires the linac to be pulsed at the PS repetition rate of 0.8 Hz with a mean beam current of 10 mA which is sufficient for filling the PS in 240 ms (i.e. about 100 turns) with the ultimate intensity foreseen for injection for the LHC. The linac is composed of two RFQs with a chopping section, a room temperature DTL, a superconducting section with reduced beta cavities up to 1 GeV, and a section of LEP2 cavities up to 2 GeV. This study deals, in particular, with the problems inherent in H- acceleration up to high energy and in the pulsed operation of SC cavities. Means for compensating microphonic vibrations in the SC cavities are considered, with the aim of reducing the final overall energy spread to the tight requirements for injection into a synchrotron. Other possible applications of such a machine are also briefly reviewed, that make use of its potential for working at a higher duty cycle than required for LHC alone