1,185 research outputs found
Entanglement of Pure Two-Mode Gaussian States
The entanglement of general pure Gaussian two-mode states is examined in
terms of the coefficients of the quadrature components of the wavefunction. The
entanglement criterion and the entanglement of formation are directly evaluated
as a function of these coefficients, without the need for deriving local
unitary transformations. These reproduce the results of other methods for the
special case of symmetric pure states which employ a relation between squeezed
states and Einstein-Podolsky-Rosen correlations. The modification of the
quadrature coefficients and the corresponding entanglement due to application
of various optical elements is also derived.Comment: 12 page
Entanglement of a Double Dot with a Quantum Point Contact
Entanglement between particle and detector is known to be inherent in the
measurement process. Gurvitz recently analyzed the coupling of an electron in a
double dot (DD) to a quantum point contact (QPC) detector. In this paper we
examine the dynamics of entanglement that result between the DD and QPC. The
rate of entanglement is optimized as a function of coupling when the electron
is initially in one of the dots. It decreases asymptotically towards zero with
increased coupling. The opposite behavior is observed when the DD is initially
in a superposition: the rate of entanglement increases unboundedly as the
coupling is increased. The possibility that there are conditions for which
measurement occurs versus entanglement is considered
Adapting a Computational Multi Agent Model for Humpback Whale Song Research for use as a Tool for Algorithmic Composition
Humpback whales (Megaptera Novaengliae) present one of the most complex displays of cultural transmission amongst non-humans. During breeding seasons, male humpback whales create long, hierarchical songs, which are shared amongst a population. Every male in the population conforms to the same song in a population. During the breeding season these songs slowly change and the song at the end of the breeding season is significantly different from the song heard at the start of the breeding season. The song of a population can also be replaced, if a new song from a different population is introduced.This is known as song revolution. Our research focuses on building computational multi agent models, which seek to recreate these phenomena observed in the wild.Our research relies on methods inspired by computational multi agent models for the evolution of music. This interdisciplinary approach has allowed us to adapt our model so that it may be used not only as a scientific tool, but also a creative tool for algorithmic composition. This paper discusses the model in detail, and then demonstrates how it may be adapted for use as an algorithmic composition tool.Publisher PD
Concordance study between the ParaDNA® Intelligence Test, a rapid DNA profiling assay, and a conventional STR typing kit (AmpFlSTR® SGM Plus®).
The ParaDNA® Intelligence Test enables STR profiling directly from human biological samples and evidence items collected from crime scene in 75min. Designed for non-expert use this system allows DNA information to be available to investigators before it would typically be available from a laboratory. The ParaDNA Intelligence Test system amplifies D3S1358, D8S119, D16S539, D18S1358 and TH01 STR loci and the gender typing locus amelogenin and detects the alleles present with HyBeacon® probes. Individual DNA samples from 381 UK Caucasian individuals were analysed using AmpFlSTR® SGM Plus® and the ParaDNA Intelligence Test with the derived STR profiles compared. Here we describe the high level of concordance demonstrated between the two systems and discuss this with reference to allele frequencies and the discriminatory power offered by the ParaDNA Intelligence Test
Structure of the Phase in Pure Two-Mode Gaussian States
The two-mode relative phase associated with Gaussian states plays an
important role in quantum information processes in optical, atomic and
electronic systems. In this work, the origin and structure of the two-mode
relative phase in pure Gaussian states is studied in terms of its dependences
on the quadratures of the modes. This is done by constructing local canonical
transformations to an associated two-mode squeezed state. The results are
illustrated by studying the time dependence of the phase under a nonlocal
unitary model evolution containing correlations between the modes. In a more
general context, this approach may allow the two-mode phase to be studied in
situations sensitive to different physical parameters within experimental
configurations relevant to quantum information processing tasks
Gate voltage dependent Rashba spin splitting in hole transverse magnetic focussing
Magnetic focussing of charge carriers in two-dimensional systems provides a
solid state version of a mass spectrometer. In the presence of a spin-orbit
interaction, the first focussing peak splits into two spin dependent peaks,
allowing focussing to be used to measure spin polarisation and the strength of
the spin-orbit interaction. In hole systems, the k^3 dependence of the Rashba
spin-orbit term allows the spatial separation of spins to be changed in-situ
using a voltage applied to an overall top gate. Here we demonstrate that this
can be used to control the splitting of the magnetic focussing peaks.
Additionally, we compare the focussing peak splitting to that predicted by
Shubnikov-de Haas oscillations and k.p bandstructure calculations. We find that
the focussing peak splitting is consistently larger than expected, suggesting
further work is needed on understanding spin dependent magnetic focussing
Spin polarisation and spin dependent scattering of holes in transverse magnetic focussing
In 2D systems with a spin-orbit interaction, magnetic focussing can be used
to create a spatial separation of particles with different spin. Here we
measure hole magnetic focussing for two different magnitudes of the Rashba
spin-orbit interaction. We find that when the Rashba spin-orbit magnitude is
large there is significant attenuation of one of the focussing peaks, which is
conventionally associated with a change in the spin polarisation. We instead
show that in hole systems with a spin-orbit interaction, this peak
suppression is due to a change in the scattering of one spin state, not a
change in spin polarisation. We also show that the change in scattering length
extracted from magnetic focussing is consistent with results obtained from
measurements of Shubnikov-de Haas oscillations. This result suggests that
scattering must be considered when relating focussing peak amplitude to spin
polarisation in hole system
Probing Fermi surface shifts with spin resolved transverse magnetic focussing
Transverse magnetic focussing is the solid state equivalent of a mass
spectrometer. It is unique among 2D measurement techniques as it is able to
measure a well defined section of the Fermi surface, making it possible to
detect changes that would be averaged out over the whole Fermi surface. Here,
we utilise this unique property to probe non-adiabatic spin dynamics and spin
dependent scattering of holes. We combine spin-resolved magnetic focussing with
an additional independent in-plane magnetic field and observe a change in
focussing peak amplitude that is not symmetric with respect to the field
direction (i.e. ), and is extremely
sensitive to the magnitude of the in-plane magnetic field. We show that the
magnetic focussing signal is extremely sensitive to small changes in the Fermi
velocity, which can be used to detect small shifts in the Fermi surface caused
by an in-plane magnetic field. We also find that focussing can be used to
detect the proximity between spin-split Fermi surfaces, which cause
non-adiabatic spin dynamics
Antenatal care service delivery and factors affecting effective tetanus vaccine coverage in low- and middle-income countries: results of the Maternal Immunisation and Antenatal Care Situational Analysis (MIACSA) project
Objectives:To map the integration of existing maternal tetanus immunization programmes within ante-natal care (ANC) services for pregnant women in low- and middle-income countries (LMICs) and to identify and understand the challenges, barriers and facilitators associated with high performance maternal vaccine service delivery.Design:A mixed methods, cross sectional study with four data collection phases including a desk review,online survey, telephone and face-to-face interviews and in country visits was undertaken between 2016 and 2018. Associations of different service delivery process components with protection at birth (PAB) andwithcountrygroupswereestablished.PABwasdefinedastheproportionofneonatesprotectedatbirthagainstneonataltetanus. Regression analysis and structural equation modelling was used to assess associations of different variables with maternal tetanus immunization coverage. Latent class analysis (LCA), was used to group country performance for maternal immunization, and to address the problem of multicollinearity.Setting:LMICs.Results: The majority of LMICs had a policy on recommended number of ANC visits, however most were yet toimplementtheWHOguidelinesrecommendingeightANCcontacts.Countriesthatrecommended>4ANC contacts were more likely to have high PAB > 90%. Passive disease surveillance was the most common form of dis-ease surveillance performed but the maternal and neonatal morbidity and mortality indicators recorded differed between countries. The presence of user fees for antenatal care and maternal immunization was significantly associated with lower PAB (<90%).Conclusions:Recommendations include implementing the current WHO ANC guideline to facilitate increased opportunities for vaccination during each pregnancy. Improved utilisation of ANC services by increasing the demand side by increasing the quality of services, reducing any associated costs and supporting user fee exemptions, or the supply side can also enhance utilisation of ANC services which are positioned as an ideal platform for delivery of maternal vaccine
Self-diffusion in binary blends of cyclic and linear polymers
A lattice model is used to estimate the self-diffusivity of entangled cyclic
and linear polymers in blends of varying compositions. To interpret simulation
results, we suggest a minimal model based on the physical idea that constraints
imposed on a cyclic polymer by infiltrating linear chains have to be released,
before it can diffuse beyond a radius of gyration. Both, the simulation, and
recently reported experimental data on entangled DNA solutions support the
simple model over a wide range of blend compositions, concentrations, and
molecular weights.Comment: 10 pages, 2 figure
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