2,330 research outputs found
Working outside the comfort of competence in a corrections centre: toward collective competence
Qualitative case study of the collective learning of staff working in a corrections centre under conditions of rapid organisational change. Conceptualises the notion of collective competence that is emergent and relationally constructed
Low Energy Singlets in the Excitation Spectrum of the Spin Tetrahedra System Cu_2Te_2O_5Br_2
Low energy Raman scattering of the s=1/2 spin tetrahedra system
Cu_2Te_2O_5Br_2 is dominated by an excitation at 18 cm^{-1} corresponding to an
energy E_S=0.6\Delta, with \Delta the spin gap of the compound. For elevated
temperatures this mode shows a soft mode-like decrease in energy pointing to an
instability of the system. The isostructural reference system Cu_2Te_2O_5Cl_2
with a presumably larger inter-tetrahedra coupling does not show such a low
energy mode. Instead its excitation spectrum and thermodynamic properties are
compatible with long range Neel-ordering. We discuss the observed effects in
the context of quantum fluctuations and competing ground states.Comment: 5 pages, 2 figures, ISSP-Kashiwa 2001, Conference on Correlated
Electron
Attosecond Control of Ionization Dynamics
Attosecond pulses can be used to initiate and control electron dynamics on a
sub-femtosecond time scale. The first step in this process occurs when an atom
absorbs an ultraviolet photon leading to the formation of an attosecond
electron wave packet (EWP). Until now, attosecond pulses have been used to
create free EWPs in the continuum, where they quickly disperse. In this paper
we use a train of attosecond pulses, synchronized to an infrared (IR) laser
field, to create a series of EWPs that are below the ionization threshold in
helium. We show that the ionization probability then becomes a function of the
delay between the IR and attosecond fields. Calculations that reproduce the
experimental results demonstrate that this ionization control results from
interference between transiently bound EWPs created by different pulses in the
train. In this way, we are able to observe, for the first time, wave packet
interference in a strongly driven atomic system.Comment: 8 pages, 4 figure
Multimode quantum limits to the linewidth of an atom laser
The linewidth of an atom laser can be limited by excitation of higher energy
modes in the source Bose-Einstein condensate, energy shifts in that condensate
due to the atomic interactions, or phase diffusion of the lasing mode due to
those interactions. The first two are effects that can be described with a
semiclassical model, and have been studied in detail for both pumped and
unpumped atom lasers. The third is a purely quantum statistical effect, and has
been studied only in zero dimensional models. We examine an unpumped atom laser
in one dimension using a quantum field theory using stochastic methods based on
the truncated Wigner approach. This allows spatial and statistical effects to
be examined simultaneously, and the linewidth limit for unpumped atom lasers is
quantified in various limits.Comment: 8 Figure
Judgements as a basis for informal workplace learning - preliminary research findings
Informal learning can be broadly characterised as learning found in everyday opportunities where learners interact with the world around them. It can be distinguished from formal learning where the purpose, structure and content for learning are imposed on the learner. When informal learning occurs in the context of work or organised settings, factors such as performance, practice, sociocultural dynamics and situational context influence its nature and quality. Previous research by Beckett, Hager and Halliday (Beckett, 1996; Beckett & Hager, 2000, 2002; Hager, 2001; Halliday & Hager, 2002) asserts that productive informal learning is better characterised as a growing capacity to make contextual-sensitive judgements - a discretionary and discriminating process that involves holistic and embodied knowing. Our paper reports on progress in an Australian Research Council funded Discovery project designed to test this judgement-as-learning approach. Detailed case studies of critical incidents in a range of workplaces are being constructed and the learning or otherwise by key players involved in these incidents is being elucidated and analysed. This empirical investigation provides a means of analysing significant workplace events in order to develop a model of informal learning and an associated theory of practice. The paper outlines the overall project rationale and discusses findings from one initial case study. Additional findings from other case studies developed after submission of this paper, will be presented and discussed at the conference
Squeezing and entanglement delay using slow light
We examine the interaction of a weak probe with atoms in a lambda-level
configuration under the conditions of electromagnetically induced transparency
(EIT). In contrast to previous works on EIT, we calculate the output state of
the resultant slowly propagating light field while taking into account the
effects of ground state dephasing and atomic noise for a more realistic model.
In particular, we propose two experiments using slow light with a nonclassical
probe field and show that two properties of the probe, entanglement and
squeezing, characterizing the quantum state of the probe field, can be
well-preserved throughout the passage.Comment: 2 figures; v2: fixed some minor typographical errors in a couple of
equations and corrected author spelling in one reference. v3: Added three
authors; changed the entaglement definition to conform to a more accepted
standard (Duan's entanglement measure); altered the abstract slightly. v4:
fixed formatting of figure
A multibeam atom laser: coherent atom beam splitting from a single far detuned laser
We report the experimental realisation of a multibeam atom laser. A single
continuous atom laser is outcoupled from a Bose-Einstein condensate (BEC) via
an optical Raman transition. The atom laser is subsequently split into up to
five atomic beams with slightly different momenta, resulting in multiple,
nearly co-propagating, coherent beams which could be of use in interferometric
experiments. The splitting process itself is a novel realization of Bragg
diffraction, driven by each of the optical Raman laser beams independently.
This presents a significantly simpler implementation of an atomic beam
splitter, one of the main elements of coherent atom optics
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