24,263 research outputs found
The impact of information and communication technology on family carers of older people and professionals in Sweden
Government policy in Sweden, as in other developed countries, pays increasing attention as to how best to support the family carers of older people. New and innovative means of support, such as information and communication technology, are emerging. This paper explores the perceived benefits of, and barriers to, information technology as a means of supporting family carers of older people.
Following a brief overview of the care-giving literature, with particular reference to the Swedish context, interview and questionnaire data collected from 34 families who took part in the Swedish ACTION project are used to explore the role of user-friendly information and communication technology to inform and enable family carers of older people to exercise choice, to care more effectively and to work in partnership with professionals. Interview data from two groups of professionals that utilised ACTION are also examined to throw light on its potential benefits for both carers and professionals. Consideration is given to the barriers to using information technology, and to identifying those carers most likely to benefit. Areas for further development are the need for practitioners' education and a wider range of programmes to address carers' diverse needs. Clearly, lessons learned from the Swedish project have wider relevance, given that new forms of support are being developed in most technically advanced countries
Spin filling of a quantum dot derived from excited-state spectroscopy
We study the spin filling of a semiconductor quantum dot using excited-state
spectroscopy in a strong magnetic field. The field is oriented in the plane of
the two-dimensional electron gas in which the dot is electrostatically defined.
By combining the observation of Zeeman splitting with our knowledge of the
absolute number of electrons, we are able to determine the ground state spin
configuration for one to five electrons occupying the dot. For four electrons,
we find a ground state spin configuration with total spin S=1, in agreement
with Hund's first rule. The electron g-factor is observed to be independent of
magnetic field and electron number.Comment: 11 pages, 7 figures, submitted to New Journal of Physics, focus issue
on Solid State Quantum Informatio
Measurement efficiency and n-shot read out of spin qubits
We consider electron spin qubits in quantum dots and define a measurement
efficiency e to characterize reliable measurements via n-shot read outs. We
propose various implementations based on a double dot and quantum point contact
(QPC) and show that the associated efficiencies e vary between 50% and 100%,
allowing single-shot read out in the latter case. We model the read out
microscopically and derive its time dynamics in terms of a generalized master
equation, calculate the QPC current and show that it allows spin read out under
realistic conditions.Comment: 5 pages, 1 figur
Inferring the three-dimensional distribution of dust in the Galaxy with a non-parametric method: Preparing for Gaia
We present a non-parametric model for inferring the three-dimensional (3D)
distribution of dust density in the Milky Way. Our approach uses the extinction
measured towards stars at different locations in the Galaxy at approximately
known distances. Each extinction measurement is proportional to the integrated
dust density along its line-of-sight. Making simple assumptions about the
spatial correlation of the dust density, we can infer the most probable 3D
distribution of dust across the entire observed region, including along sight
lines which were not observed. This is possible because our model employs a
Gaussian Process to connect all lines-of-sight. We demonstrate the capability
of our model to capture detailed dust density variations using mock data as
well as simulated data from the Gaia Universe Model Snapshot. We then apply our
method to a sample of giant stars observed by APOGEE and Kepler to construct a
3D dust map over a small region of the Galaxy. Due to our smoothness constraint
and its isotropy, we provide one of the first maps which does not show the
"fingers of god" effect.Comment: Minor changes applied. Final version accepted for publication in A&A.
15 pages, 17 figure
Real-time detection of single electron tunneling using a quantum point contact
We observe individual tunnel events of a single electron between a quantum
dot and a reservoir, using a nearby quantum point contact (QPC) as a charge
meter. The QPC is capacitively coupled to the dot, and the QPC conductance
changes by about 1% if the number of electrons on the dot changes by one. The
QPC is voltage biased and the current is monitored with an IV-convertor at room
temperature. We can resolve tunnel events separated by only 8 s, limited
by noise from the IV-convertor. Shot noise in the QPC sets a 25 ns lower bound
on the accessible timescales.Comment: 3 pages, 3 figures, submitte
Measurement of exciton correlations using electrostatic lattices
We present a method for determining correlations in a gas of indirect
excitons in a semiconductor quantum well structure. The method involves
subjecting the excitons to a periodic electrostatic potential that causes
modulations of the exciton density and photoluminescence (PL). Experimentally
measured amplitudes of energy and intensity modulations of exciton PL serve as
an input to a theoretical estimate of the exciton correlation parameter and
temperature. We also present a proof-of-principle demonstration of the method
for determining the correlation parameter and discuss how its accuracy can be
improved.Comment: 10 pages, 11 figure
Single-shot readout of electron spin states in a quantum dot using spin-dependent tunnel rates
We present a method for reading out the spin state of electrons in a quantum
dot that is robust against charge noise and can be used even when the electron
temperature exceeds the energy splitting between the states. The spin states
are first correlated to different charge states using a spin dependence of the
tunnel rates. A subsequent fast measurement of the charge on the dot then
reveals the original spin state. We experimentally demonstrate the method by
performing read-out of the two-electron spin states, achieving a single-shot
visibility of more than 80%. We find very long triplet-to-singlet relaxation
times (up to several milliseconds), with a strong dependence on in-plane
magnetic field.Comment: 4 pages, 4 figure
Semiconductor few-electron quantum dot operated as a bipolar spin filter
We study the spin states of a few-electron quantum dot defined in a
two-dimensional electron gas, by applying a large in-plane magnetic field. We
observe the Zeeman splitting of the two-electron spin triplet states. Also, the
one-electron Zeeman splitting is clearly resolved at both the zero-to-one and
the one-to-two electron transition. Since the spin of the electrons transmitted
through the dot is opposite at these two transitions, this device can be
employed as an electrically tunable, bipolar spin filter. Calculations and
measurements show that higher-order tunnel processes and spin-orbit interaction
have a negligible effect on the polarization.Comment: 4 pages, 3 figure
Zero Temperature Phase Transition in Spin-ladders: Phase Diagram and Dynamical studies of Cu(Hp)Cl
In a magnetic field, spin-ladders undergo two zero-temperature phase
transitions at the critical fields Hc1 and Hc2. An experimental review of
static and dynamical properties of spin-ladders close to these critical points
is presented. The scaling functions, universal to all quantum critical points
in one-dimension, are extracted from (a) the thermodynamic quantities
(magnetization) and (b) the dynamical functions (NMR relaxation). A simple
mapping of strongly coupled spin ladders in a magnetic field on the exactly
solvable XXZ model enables to make detailed fits and gives an overall
understanding of a broad class of quantum magnets in their gapless phase
(between Hc1 and Hc2). In this phase, the low temperature divergence of the NMR
relaxation demonstrates its Luttinger liquid nature as well as the novel
quantum critical regime at higher temperature. The general behaviour close
these quantum critical points can be tied to known models of quantum magnetism.Comment: few corrections made, 15 pages, to be published in European Journal
of Physics
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