791 research outputs found
Point Estimation of States of Finite Quantum Systems
The estimation of the density matrix of a -level quantum system is studied
when the parametrization is given by the real and imaginary part of the entries
and they are estimated by independent measurements. It is established that the
properties of the estimation procedure depend very much on the invertibility of
the true state. In particular, in case of a pure state the estimation is less
efficient. Moreover, several estimation schemes are compared for the unknown
state of a qubit when one copy is measured at a time. It is shown that the
average mean quadratic error matrix is the smallest if the applied observables
are complementary. The results are illustrated by computer simulations.Comment: 16 pages, 5 figure
Inhomogeneous low temperature epitaxial breakdown during Si overgrowth of GeSi quantum dots
Low temperature epitaxial breakdown of inhomogeneously strained Si capping
layers is investigated. By growing Si films on coherently strained GeSi quantum
dot surfaces, we differentiate effects of surface roughness, strain, and growth
orientation on the mechanism of epitaxial breakdown. Using atomic force
microscopy and high resolution cross-sectional transmission electron microscopy
we find that while local lattice strain up to 2% has a negligible effect,
growth on higher-index facets such as {113} significantly reduces the local
breakdown thickness. Nanoscale growth mound formation is observed above all
facet orientations. Since diffusion lengths depend directly on the surface
orientation, we relate the variation in epitaxial thickness to the low
temperature stability of specific growth facets and on the average size of
kinetically limited growth mounds.Comment: 6 pages, 6 figures, submitted to the Journal of Applied Physic
On Mutual Information in Multipartite Quantum States and Equality in Strong Subadditivity of Entropy
The challenge of equality in the strong subadditivity inequality of entropy
is approached via a general additivity of correlation information in terms of
nonoverlapping clusters of subsystems in multipartite states (density
operators). A family of tripartite states satisfying equality is derived.Comment: 8 pages; Latex2e and Revtex
The missing link? Design for all elements in ICT education fostering e-inclusion.
Accessible Information and Communication Technology (ICT) systems and applications are able to offer an important opportunity for social, political and economic engagement.
Additionally, the established principles and practices of Design for All could help to minimise the risk of exclusion of citizens from the information society such as older adults, disabled people, people with low literacy or those not using their first language But what if the future providers of ICT solutions and applications lack the knowledge of Design for All principles and practices, and the skills to apply that knowledge to support innovation and advancement
Covariance and Fisher information in quantum mechanics
Variance and Fisher information are ingredients of the Cramer-Rao inequality.
We regard Fisher information as a Riemannian metric on a quantum statistical
manifold and choose monotonicity under coarse graining as the fundamental
property of variance and Fisher information. In this approach we show that
there is a kind of dual one-to-one correspondence between the candidates of the
two concepts. We emphasis that Fisher informations are obtained from relative
entropies as contrast functions on the state space and argue that the scalar
curvature might be interpreted as an uncertainty density on a statistical
manifold.Comment: LATE
Design for all as focus in European ICT teaching and training activities.
Both in the EU and UK the goal of digital inclusion demands a broad understanding of the factors that contribute to the risk of exclusion, such as a result of age, disability, low literacy, geography and ethnicity. The overall methodologies and principles of Design for All are well established and address many of the challenges of design for user diversity including older and disabled people. However, these are not yet an established part of the curriculum in mainstream Computing and Information and Communications Technology (ICT) in higher level education.
The Design for All @eInclusion project investigated the current provision of education and training of future developers and associated disciplines and identified progress and gaps. Best practice included examples of specialist modules and âhidden gemsâ â instances of small elements such as single lectures that are optional, integrated or embedded within a larger module. These findings contributed to the development of curriculum guidelines which take account of the latest agreements for European harmonisation through the European Qualifications Framework. These guidelines are intended to stimulate the creation of new courses throughout Europe
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