13,967 research outputs found
Treatment approaches for dual diagnosis clients in England
Introduction - Dual diagnosis (DD, co-occurrence of substance use and mental health problems) prevalence data in England are limited to specific regions and reported rates vary widely. Reliable information on actual service provision for dual diagnosis clients has not been collated. Thus a national survey was carried out to estimate dual diagnosis prevalence in treatment populations and describe the service provision available for this client population in drug/alcohol (DAS) and mental health services (MHS). Design - A questionnaire was sent to managers of 706 DAS and 2374 MHS. Overall, 249 (39%) DAS and 493 (23%) MHS participated in the survey. Results - In both DAS and MHS, around 32% of clients were estimated to have dual diagnosis problems. However, fewer than 50% of services reported assessing clients for both problem areas. Regarding specific treatment approaches, most services (DAS: 88%, MHS: 87%) indicated working jointly with other agencies. Significantly fewer services used joint protocols (DAS: 55%, MHS: 48%) or shared care arrangements, including access to external drug/alcohol or mental health teams (DAS: 47%, MHS: 54%). Only 25% of DAS and 17% of MHS employed dual diagnosis specialists. Conclusions - Dual diagnosis clients constitute a substantial proportion of clients in both DAS and MHS in England. Despite recent policy initiatives, joint working approaches tend to remain unstructured
Optimal Control for Generating Quantum Gates in Open Dissipative Systems
Optimal control methods for implementing quantum modules with least amount of
relaxative loss are devised to give best approximations to unitary gates under
relaxation. The potential gain by optimal control using relaxation parameters
against time-optimal control is explored and exemplified in numerical and in
algebraic terms: it is the method of choice to govern quantum systems within
subspaces of weak relaxation whenever the drift Hamiltonian would otherwise
drive the system through fast decaying modes. In a standard model system
generalising decoherence-free subspaces to more realistic scenarios,
openGRAPE-derived controls realise a CNOT with fidelities beyond 95% instead of
at most 15% for a standard Trotter expansion. As additional benefit it requires
control fields orders of magnitude lower than the bang-bang decouplings in the
latter.Comment: largely expanded version, superseedes v1: 10 pages, 5 figure
Ramsey interferometry with generalized one-axis twisting echoes
We consider a large class of Ramsey interferometry protocols which are
enhanced by squeezing and un-squeezing operations before and after a phase
signal is imprinted on the collective spin of particles. We report an
analytical optimization for any given particle number and strengths of
(un-)squeezing. These results can be applied even when experimentally relevant
decoherence processes during the squeezing and un-squeezing interactions are
included. Noise between the two interactions is however not considered in this
work. This provides a generalized characterization of squeezing echo protocols,
recovering a number of known quantum metrological protocols as local
sensitivity maxima, thereby proving their optimality. We discover a single new
protocol. Its sensitivity enhancement relies on a double inversion of
squeezing. In the general class of echo protocols, the newly found
over-un-twisting protocol is singled out due to its Heisenberg scaling even at
strong collective dephasing.Comment: 11+8 pages, 7 figures, comments welcome! ; accepted versio
Modelling and Measurement of Charge Transfer in Multiple GEM Structures
Measurements and numerical simulations on the charge transfer in Gas Electron
Multiplier (GEM) foils are presented and their implications for the usage of
GEM foils in Time Projection Chambers are discussed. A small test chamber has
been constructed and operated with up to three GEM foils. The charge transfer
parameters derived from the electrical currents monitored during the
irradiation with an Fe-55 source are compared with numerical simulations. The
performance in magnetic fields up to 2 T is also investigated.Comment: 21 pages, 16 figures, submitted to NIM-
Electron spin resonance on a 2-dimensional electron gas in a single AlAs quantum well
Direct electron spin resonance (ESR) on a high mobility two dimensional
electron gas in a single AlAs quantum well reveals an electronic -factor of
1.991 at 9.35 GHz and 1.989 at 34 GHz with a minimum linewidth of 7 Gauss. The
ESR amplitude and its temperature dependence suggest that the signal originates
from the effective magnetic field caused by the spin orbit-interaction and a
modulation of the electron wavevector caused by the microwave electric field.
This contrasts markedly to conventional ESR that detects through the microwave
magnetic field.Comment: 4 pages, 4 figure
The landscape of quantum transitions driven by single-qubit unitary transformations with implications for entanglement
This paper considers the control landscape of quantum transitions in
multi-qubit systems driven by unitary transformations with single-qubit
interaction terms. The two-qubit case is fully analyzed to reveal the features
of the landscape including the nature of the absolute maximum and minimum, the
saddle points and the absence of traps. The results permit calculating the
Schmidt state starting from an arbitrary two-qubit state following the local
gradient flow. The analysis of multi-qubit systems is more challenging, but the
generalized Schmidt states may also be located by following the local gradient
flow. Finally, we show the relation between the generalized Schmidt states and
the entanglement measure based on the Bures distance
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