3,002 research outputs found
The re-emission spectrum of digital hardware subjected to EMI
The emission spectrum of digital hardware under the influence of external electromagnetic interference is shown to contain information about the interaction of the incident energy with the digital circuits in the system. The generation mechanism of the re-emission spectrum is reviewed, describing how nonlinear effects may be a precursor to the failure of the equipment under test. Measurements on a simple circuit are used to demonstrate how the characteristics of the re-emission spectrum may be correlated with changes to the digital waveform within the circuit. The technique is also applied to a piece of complex digital hardware where Similar, though more subtle, effects can be measured. It is shown that the re-emission spectrum can be used to detect the interaction of the interference with the digital devices at a level well below that which is able to cause static failures in the circuits. The utility of the technique as a diagnostic tool for immunity testing of digital hardware, by identifying which subsystems are being affected by external interference, is also demonstrated
Topological Qubit Design and Leakage
We examine how best to design qubits for use in topological quantum
computation. These qubits are topological Hilbert spaces associated with small
groups of anyons. Op- erations are performed on these by exchanging the anyons.
One might argue that, in order to have as many simple single qubit operations
as possible, the number of anyons per group should be maximized. However, we
show that there is a maximal number of particles per qubit, namely 4, and more
generally a maximal number of particles for qudits of dimension d. We also look
at the possibility of having topological qubits for which one can perform
two-qubit gates without leakage into non-computational states. It turns out
that the requirement that all two-qubit gates are leakage free is very
restrictive and this property can only be realized for two-qubit systems
related to Ising-like anyon models, which do not allow for universal quantum
computation by braiding. Our results follow directly from the representation
theory of braid groups which means they are valid for all anyon models. We also
make some remarks on generalizations to other exchange groups.Comment: 13 pages, 3 figure
Experimental confirmation of the low B isotope coefficient in MgB2
Recent investigations have shown that the first proposed explanations of the
disagreement between experimental and theoretical value of isotope coefficient
in MgB2 need to be reconsidered. Considering that in samples with residual
resistivity of few mu-Ohm cm critical temperature variations produced by
disorder effects can be comparable with variations due to the isotopic effect,
we adopt a procedure in evaluating the B isotope coefficient which take account
of these effects, obtaining a value which is in agreement with previous results
and then confirming that there is something still unclear in the physics of
MgB2.Comment: 8 pages, 3 figures Title has been changed A statement has been added
in page 7 of the pdf file "Finally we would..." Reference 21 has been added
Figure 1 anf Figure 2 have been change
Suppression of the critical temperature of superconducting NdFeAs(OF) single crystals by Kondo-like defect sites induced by alpha-particle irradiation
We report a comprehensive investigation of the suppression of the critical
temperature Tc of NdFeAs(OF) single crystal by alpha-particle irradiation. Our
data indicate that irradiation defects produce both nonmagnetic and magnetic
scattering, resulting in the Kondo-like excess resistance over 2 decades in temperatures above . Despite high densities of
irradiation defects, the dose at which is suppressed to zero is
comparable to that for MgB2 but is well above the corresponding values for
cuprates.Comment: 11 pages, 4 figure
Population structure of Canarium labiatum (Röding, 1798) (Mollusca: Neostromboidae: Strombidae) on Green Island, Great Barrier Reef, Queensland
Canarium labiatum is a small gastropod of the Strombidae family that is commonly encountered in the inter-tidal zones of tropical Queensland, Australia, yet little is known of its population structure. A targeted survey of the Canarium labiatum population on Green Island, located near Cairns, Queensland, was conducted on 12 August 2015. Ninety adult specimens were collected, of which 49 were female and 41 were male. The sample demonstrated significant sexual axiallength size dimorphism, with a bias towards larger females. While we collected more females than males, this did not represent a statistically significant bias, and rather may reflect the clustering nature of the sample. In addition, there was no evidence of pseudohermaphroditism in females within the population under consideration. Interestingly, 11.1% of the sample did not show banding and brown/grey-blue maculations on a light grey shell, the typical colour pattern associated with Canarium labiatum. This paper fills a knowledge gap in Queensland’s Canarium labiatum population structure and provides a basis for a wider study into the size dynamics of Strombidae in general, but Canarium in particular
Effect of oxygen incorporation on normal and superconducting properties of MgB2 films
Oxygen was systematically incorporated in MBE grown MgB2 films using in-situ
post-growth anneals in an oxygen environment. Connectivity analysis in
combination with measurements of the critical temperature and resistivity
indicate that oxygen is distributed both within and between the grains. High
values of critical current densities in field (~4x10^5 A/cm^2 at 8 T and 4.2
K), extrabolated critical fields (>45 T) and slopes of critical field versus
temperature (1.4 T/K) are observed. Our results suggest that low growth
temperatures (300oC) and oxygen doping (>0.65%) can produce MgB2 with high Jc
values in field and Hc2 for high-field magnet applications.Comment: 10 pages, 3 figure
Two-Channel Kondo Effects in Al/AlO/Sc Planar Tunnel Junctions
We have measured the differential conductances in several
Al/AlO/Sc planar tunnel junctions between 2 and 35 K. As the temperature
decreases to 16 K, the zero-bias conductance crosses over from
a standard ln dependence to a novel dependence.
Correspondingly, the finite bias conductance reveals a two-channel
Kondo scaling behavior between 4 and 16 K. The observed two-channel
Kondo physics is ascribed to originating from a few localized spin- Sc
atoms situated slightly inside the AlO/Sc interface.Comment: 4 pages, 3 figures. Phys. Rev. B (accepted
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