5,401 research outputs found
High-efficiency WSi superconducting nanowire single-photon detectors for quantum state engineering in the near infrared
We report on high-efficiency superconducting nanowire single-photon detectors
based on amorphous WSi and optimized at 1064 nm. At an operating temperature of
1.8 K, we demonstrated a 93% system detection efficiency at this wavelength
with a dark noise of a few counts per second. Combined with cavity-enhanced
spontaneous parametric down-conversion, this fiber-coupled detector enabled us
to generate narrowband single photons with a heralding efficiency greater than
90% and a high spectral brightness of
photons/(smWMHz). Beyond single-photon generation at large rate,
such high-efficiency detectors open the path to efficient multiple-photon
heralding and complex quantum state engineering
Demonstration of Einstein-Podolsky-Rosen Steering Using Hybrid Continuous- and Discrete-Variable Entanglement of Light
Einstein-Podolsky-Rosen steering is known to be a key resource for one-sided
device-independent quantum information protocols. Here we demonstrate steering
using hybrid entanglement between continuous- and discrete-variable optical
qubits. To this end, we report on suitable steering inequalities and detail the
implementation and requirements for this demonstration. Steering is
experimentally certified by observing a violation by more than 5 standard
deviations. Our results illustrate the potential of optical hybrid entanglement
for applications in heterogeneous quantum networks that would interconnect
disparate physical platforms and encodings
Photo-to-heat conversion of broadband metamaterial absorbers based on TiN nanoparticles under laser and solar illumination
We theoretically investigate photothermal heating of ultra-flexible
metamaterials, which are obtained by randomly mixing TiN nanoparticles in
polydimethylsiloxane (PDMS). Due to the plasmonic properties of TiN
nanoparticles, incident light is perfectly absorbed in a broadband range
(300-3000 nm) to generate heat within these metamaterials. Under irradiation of
an 808 nm near-infrared laser with different intensities, our predicted
temperature rises as a function of time agree well with recent experimental
data. For a given laser intensity, the temperature rise varies
non-monotonically with concentration of TiN nanoparticles because the
enhancement of thermal conductivity and absorbed energy as adding plasmonic
nanostructures leads to opposite effects on the heating process. When the model
is extended to solar heating, photothermal behaviors are qualitatively similar
but the temperature increase is less than 13 . Our studies would provide
good guidance for future experimental studies on the photo-to-heat conversion
of broadband perfect absorbers.Comment: 8 pages, 7 figures, accepted for publications in Materials Today
Communication
Confinement effect on solar thermal heating process of TiN solutions
We propose a theoretical approach to describe quantitatively the heating
process in aqueous solutions of dispersed TiN nanoparticles under solar
illumination. The temperature gradients of solution with different
concentrations of TiN nanoparticles are calculated when confinement effects of
the container on the solar absorption are taken into account. We find that the
average penetration of solar radiation into the solution is significantly
reduced with increasing the nanoparticle concentration. At high concentrations,
our numerical results show that photons are localized near the surface of the
solution. Moreover, the heat energy balance equation at the vapor-liquid
interface is used to describe the solar steam generation. The theoretical time
dependence of temperature rise and vaporization weight losses is consistent
with experiments. Our calculations give strong evidence that the substantially
localized heating near the vapor-liquid interface is the main reason for the
more efficient steam generation process by floating plasmonic membranes when
compared to randomly dispersed nanoparticles. The validated theoretical model
suggests that our approach can be applied towards new predictions and other
experimental data descriptions.Comment: 6 pages, 3 figures, accepted for publication in PCC
Election turnout statistics in many countries: similarities, differences, and a diffusive field model for decision-making
We study in details the turnout rate statistics for 77 elections in 11
different countries. We show that the empirical results established in a
previous paper for French elections appear to hold much more generally. We find
in particular that the spatial correlation of turnout rates decay
logarithmically with distance in all cases. This result is quantitatively
reproduced by a decision model that assumes that each voter makes his mind as a
result of three influence terms: one totally idiosyncratic component, one
city-specific term with short-ranged fluctuations in space, and one long-ranged
correlated field which propagates diffusively in space. A detailed analysis
reveals several interesting features: for example, different countries have
different degrees of local heterogeneities and seem to be characterized by a
different propensity for individuals to conform to the cultural norm. We
furthermore find clear signs of herding (i.e. strongly correlated decisions at
the individual level) in some countries, but not in others.Comment: 15 pages, 9 figures, 7 table
Identifying factors for job motivation of rural health workers in North Viet Nam
BACKGROUND: In Viet Nam, most of the public health staff (84%) currently works in rural areas, where 80% of the people live. To provide good quality health care services, it is important to develop strategies influencing staff motivation for better performance. METHOD: An exploratory qualitative research was carried out among health workers in two provinces in North Viet Nam so as to identify entry points for developing strategies that improve staff performance in rural areas. The study aimed to determine the major motivating factors and it is the first in Viet Nam that looks at health workers' job perception and motivation. Apart from health workers, managers at national and at provincial level were interviewed as well as some community representatives. RESULTS: The study showed that motivation is influenced by both financial and non-financial incentives. The main motivating factors for health workers were appreciation by managers, colleagues and the community, a stable job and income and training. The main discouraging factors were related to low salaries and difficult working conditions. CONCLUSION: Activities associated with appreciation such as performance management are currently not optimally implemented, as health workers perceive supervision as control, selection for training as unclear and unequal, and performance appraisal as not useful. The kind of non-financial incentives identified should be taken into consideration when developing HRM strategies. Areas for further studies are identified
Visualizing landscapes of the superconducting gap in heterogeneous superconductor thin films: geometric influences on proximity effects
The proximity effect is a central feature of superconducting junctions as it
underlies many important applications in devices and can be exploited in the
design of new systems with novel quantum functionality. Recently, exotic
proximity effects have been observed in various systems, such as
superconductor-metallic nanowires and graphene-superconductor structures.
However, it is still not clear how superconducting order propagates spatially
in a heterogeneous superconductor system. Here we report intriguing influences
of junction geometry on the proximity effect for a 2D heterogeneous
superconductor system comprised of 2D superconducting islands on top of a
surface metal. Depending on the local geometry, the superconducting gap induced
in the surface metal region can either be confined to the boundary of the
superconductor, in which the gap decays within a short distance (~ 15 nm), or
can be observed nearly uniformly over a distance of many coherence lengths due
to non-local proximity effects.Comment: 17 pages, 4 figure
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