142,878 research outputs found
A tutorial task and tertiary courseware model for collaborative learning communities
RAED provides a computerised infrastructure to support the development and administration of Vicarious Learning in collaborative learning communities spread across multiple universities and workplaces. The system is based on the OASIS middleware for Role-based Access Control. This paper describes the origins of the model and the approach to implementation and outlines some of its benefits to collaborative teachers and learners
Designer quantum states of matter created atom-by-atom
With the advances in high resolution and spin-resolved scanning tunneling
microscopy as well as atomic-scale manipulation, it has become possible to
create and characterize quantum states of matter bottom-up, atom-by-atom. This
is largely based on controlling the particle- or wave-like nature of electrons,
as well as the interactions between spins, electrons, and orbitals and their
interplay with structure and dimensionality. We review the recent advances in
creating artificial electronic and spin lattices that lead to various exotic
quantum phases of matter, ranging from topological Dirac dispersion to complex
magnetic order. We also project future perspectives in non-equilibrium
dynamics, prototype technologies, engineered quantum phase transitions and
topology, as well as the evolution of complexity from simplicity in this newly
developing field
Transport dynamics of ultracold atoms in a triple-well transistor-like potential
The transport of atoms is experimentally studied in a transistor-like
triple-well potential consisting of a narrow gate well surrounded by source and
drain wells. Atoms are initially loaded into the source well with
pre-determined temperature and chemical potential. Energetic atoms flow from
the source, across the gate, and into the drain where they are removed using a
resonant light beam. The manifestation of atom-atom interactions and
dissipation is evidenced by a rapid population growth in the initially vacant
gate well. The transport dynamics are shown to depend strongly on a feedback
parameter determined by the relative heights of the two barriers forming the
gate region. For a range of feedback parameter values, experiments establish
that the gate atoms develop a larger chemical potential and lower temperature
than those in the source.Comment: 13 pages, 5 figures, accepted for publication in NJ
Measurement Protocol for the Entanglement Spectrum of Cold Atoms
Entanglement, and, in particular the entanglement spectrum, plays a major
role in characterizing many-body quantum systems. While there has been a surge
of theoretical works on the subject, no experimental measurement has been
performed to date because of the lack of an implementable measurement scheme.
Here, we propose a measurement protocol to access the entanglement spectrum of
many-body states in experiments with cold atoms in optical lattices. Our scheme
effectively performs a Ramsey spectroscopy of the entanglement Hamiltonian and
is based on the ability to produce several copies of the state under
investigation together with the possibility to perform a global swap gate
between two copies conditioned on the state of an auxiliary qubit. We show how
the required conditional swap gate can be implemented with cold atoms, either
by using Rydberg interactions or coupling the atoms to a cavity mode. We
illustrate these ideas on a simple (extended) Bose-Hubbard model where such a
measurement protocol reveals topological features of the Haldane phase
SFDL: MVC Applied to Workflow Design
Process management based on workflow systems is a growing trend in collaborative environments. One of the most notorious areas of improvement is that of user interfaces, especially since business process definition languages do not address efficiently the point of contact between workflow engines and human interactions. With that in focus, we propose the MVC pattern design to workflow systems. To accomplish this, we have designed a new dynamic view definition language called SFDL, oriented towards the easy interoperability with the different workflow definition languages, while maintaining enough flexibility to be represented in different formats and being adaptable to several environments. To validate our approach, we have carried out an implementation in a real banking scenario, which has provided continuous feedback and enabled us to refine the proposal. The work is fully based on widely accepted and used web standards (XML, YAML, JSON, Atom and REST). Some guidelines are given to facilitate the adoption of our solution
Wireless network control of interacting Rydberg atoms
We identify a relation between the dynamics of ultracold Rydberg gases in
which atoms experience a strong dipole blockade and spontaneous emission, and a
stochastic process that models certain wireless random-access networks. We then
transfer insights and techniques initially developed for these wireless
networks to the realm of Rydberg gases, and explain how the Rydberg gas can be
driven into crystal formations using our understanding of wireless networks.
Finally, we propose a method to determine Rabi frequencies (laser intensities)
such that particles in the Rydberg gas are excited with specified target
excitation probabilities, providing control over mixed-state populations.Comment: 6 pages, 7 figures; includes corrections and improvements from the
peer-review proces
SWI-Prolog and the Web
Where Prolog is commonly seen as a component in a Web application that is
either embedded or communicates using a proprietary protocol, we propose an
architecture where Prolog communicates to other components in a Web application
using the standard HTTP protocol. By avoiding embedding in external Web servers
development and deployment become much easier. To support this architecture, in
addition to the transfer protocol, we must also support parsing, representing
and generating the key Web document types such as HTML, XML and RDF.
This paper motivates the design decisions in the libraries and extensions to
Prolog for handling Web documents and protocols. The design has been guided by
the requirement to handle large documents efficiently. The described libraries
support a wide range of Web applications ranging from HTML and XML documents to
Semantic Web RDF processing.
To appear in Theory and Practice of Logic Programming (TPLP)Comment: 31 pages, 24 figures and 2 tables. To appear in Theory and Practice
of Logic Programming (TPLP
Quantum Many-Body Phenomena in Coupled Cavity Arrays
The increasing level of experimental control over atomic and optical systems
gained in the past years have paved the way for the exploration of new physical
regimes in quantum optics and atomic physics, characterised by the appearance
of quantum many-body phenomena, originally encountered only in condensed-matter
physics, and the possibility of experimentally accessing them in a more
controlled manner. In this review article we survey recent theoretical studies
concerning the use of cavity quantum electrodynamics to create quantum
many-body systems. Based on recent experimental progress in the fabrication of
arrays of interacting micro-cavities and on their coupling to atomic-like
structures in several different physical architectures, we review proposals on
the realisation of paradigmatic many-body models in such systems, such as the
Bose-Hubbard and the anisotropic Heisenberg models. Such arrays of coupled
cavities offer interesting properties as simulators of quantum many-body
physics, including the full addressability of individual sites and the
accessibility of inhomogeneous models.Comment: overview article, 27 pages, 31 figure
Core TuLiP
We propose CoreTuLiP - the core of a trust management language based on Logic Programming. CoreTuLiP is based on a subset of moded logic programming, but enjoys the features of TM languages such as RT; in particular clauses are issued by different authorities and stored in a distributed manner. We present a lookup and inference algorithm which we prove to be correct and complete w.r.t. the declarative semantics. CoreTuLiP enjoys uniform syntax and the well-established semantics and is expressive enough to model scenarios which are hard to deal with in RT
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