6,421 research outputs found
Generation of indistinguishable and pure heralded single photons with tunable bandwidth
We describe a new scheme to fully control the joint spectrum of paired
photons generated in spontaneous parametric down-conversion. We show the
capability of this method to generate frequency-uncorrelated photon pairs that
are pure and indistinguishable, and whose bandwidth can be readily tuned.
Importantly, the scheme we propose here can be implemented in any nonlinear
crystal and frequency band of interest.Comment: 3 pages, 3 figure
Generation of tunable entanglement and violation of a Bell-like inequality between different degrees of freedom of a single photon
We demonstrate a scheme to generate noncoherent and coherent correlations,
i.e., a tunable degree of entanglement, between degrees of freedom of a single
photon. Its nature is analogous to the tuning of the purity (first-order
coherence) of a single photon forming part of a two-photon state by tailoring
the correlations between the paired photons. Therefore, well-known tools such
as the Clauser-Horne-Shimony-Holt (CHSH) Bell-like inequality can also be used
to characterize entanglement between degrees of freedom. More specifically,
CHSH inequality tests are performed, making use of the polarization and the
spatial shape of a single photon. The four modes required are two polarization
modes and two spatial modes with different orbital angular momentum.Comment: 7 pages, 5 figures. Updated to be consistent with published versio
Genetic analysis and management in small populations: the Asturcon pony as an example
International audienc
Quantum simulation of Anderson and Kondo lattices with superconducting qubits
We introduce a mapping between a variety of superconducting circuits and a
family of Hamiltonians describing localized magnetic impurities interacting
with conduction bands. This includes the Anderson model, the single impurity
one- and two-channel Kondo problem, as well as the 1D Kondo lattice. We compare
the requirements for performing quantum simulations using the proposed circuits
to those of universal quantum computation with superconducting qubits, singling
out the specific challenges that will have to be addressed.Comment: Longer versio
Super-Nernstian Shifts of Interfacial Proton-Coupled Electron Transfers : Origin and Effect of Noncovalent Interactions
The support of the University of Aberdeen is gratefully acknowledged. C.W. acknowledges a summer studentship from the Carnegie Trust for the Universities of Scotland. E.P.M.L. acknowledges SeCYT (Universidad Nacional de Cordoba), ́ CONICET- PIP 11220110100992, Program BID (PICT 2012-2324), and PME 2006-01581 for financial support.Peer reviewedPostprin
Shape of the spatial mode function of photons generated in noncollinear spontaneous parametric downconversion
We show experimentally how noncollinear geometries in spontaneous parametric
downconversion induce ellipticity of the shape of the spatial mode function.
The degree of ellipticity depends on the pump beam width, especially for highly
focused beams. We also discuss the ellipticity induced by the spectrum of the
pump beam
Evaluating the impact of policies recommending PrEP to subpopulations of men and transgender women who have sex with men based on demographic and behavioral risk factors.
IntroductionDeveloping guidelines to inform the use of antiretroviral pre-exposure prophylaxis (PrEP) for HIV prevention in resource-limited settings must necessarily be informed by considering the resources and infrastructure needed for PrEP delivery. We describe an approach that identifies subpopulations of cisgender men who have sex with men (MSM) and transgender women (TGW) to prioritize for the rollout of PrEP in resource-limited settings.MethodsWe use data from the iPrEx study, a multi-national phase III study of PrEP for HIV prevention in MSM/TGW, to build statistical models that identify subpopulations at high risk of HIV acquisition without PrEP, and with high expected PrEP benefit. We then evaluate empirically the population impact of policies recommending PrEP to these subpopulations, and contrast these with existing policies.ResultsA policy recommending PrEP to a high risk subpopulation of MSM/TGW reporting condomless receptive anal intercourse over the last 3 months (estimated 3.3% 1-year HIV incidence) yields an estimated 1.95% absolute reduction in 1-year HIV incidence at the population level, and 3.83% reduction over 2 years. Importantly, such a policy requires rolling PrEP out to just 59.7% of MSM/TGW in the iPrEx population. We find that this policy is identical to that which prioritizes MSM/TGW with high expected PrEP benefit. It is estimated to achieve nearly the same reduction in HIV incidence as the PrEP guideline put forth by the US Centers for Disease Control, which relies on the measurement of more behavioral risk factors and which would recommend PrEP to a larger subset of the MSM/TGW population (86% vs. 60%).ConclusionsThese findings may be used to focus future mathematical modelling studies of PrEP in resource-limited settings on prioritizing PrEP for high-risk subpopulations of MSM/TGW. The statistical approach we took could be employed to develop PrEP policies for other at-risk populations and resource-limited settings
- …