151 research outputs found
Analysis of Elliptically Polarized Maximally Entangled States for Bell Inequality Tests
When elliptically polarized maximally entangled states are considered, i.e.,
states having a non random phase factor between the two bipartite polarization
components, the standard settings used for optimal violation of Bell
inequalities are no longer adapted. One way to retrieve the maximal amount of
violation is to compensate for this phase while keeping the standard Bell
inequality analysis settings. We propose in this paper a general theoretical
approach that allows determining and adjusting the phase of elliptically
polarized maximally entangled states in order to optimize the violation of Bell
inequalities. The formalism is also applied to several suggested experimental
phase compensation schemes. In order to emphasize the simplicity and relevance
of our approach, we also describe an experimental implementation using a
standard Soleil-Babinet phase compensator. This device is employed to correct
the phase that appears in the maximally entangled state generated from a
type-II nonlinear photon-pair source after the photons are created and
distributed over fiber channels.Comment: 8 page
Autonomous detection and anticipation of jam fronts from messages propagated by inter-vehicle communication
In this paper, a minimalist, completely distributed freeway traffic
information system is introduced. It involves an autonomous, vehicle-based jam
front detection, the information transmission via inter-vehicle communication,
and the forecast of the spatial position of jam fronts by reconstructing the
spatiotemporal traffic situation based on the transmitted information. The
whole system is simulated with an integrated traffic simulator, that is based
on a realistic microscopic traffic model for longitudinal movements and lane
changes. The function of its communication module has been explicitly validated
by comparing the simulation results with analytical calculations. By means of
simulations, we show that the algorithms for a congestion-front recognition,
message transmission, and processing predict reliably the existence and
position of jam fronts for vehicle equipment rates as low as 3%. A reliable
mode of operation already for small market penetrations is crucial for the
successful introduction of inter-vehicle communication. The short-term
prediction of jam fronts is not only useful for the driver, but is essential
for enhancing road safety and road capacity by intelligent adaptive cruise
control systems.Comment: Published in the Proceedings of the Annual Meeting of the
Transportation Research Board 200
Study of ^194 Ir via thermal neutron capture and (d,p) reactions
Levels of ^194 Ir were studied using thermal neutron capture reaction. A pair spectrometer was used to measure the high-energy gamma-ray spectrum from thermal-neutron capture in enriched ^193 Ir target over the energy range 4640 - 6100 keV. The low-energy gamma-radiation from the reaction was studied with crystal diffraction spectrometers, and conversion electrons were observed with magnetic spectrometers. The high-sensitivity measurements at the Grenoble reactor, evaluated for transition energies up to 500 keV, are compared with lower-sensitivity measurements at the Wuerenlingen and Salaspils reactors. The comparison helped to obtain reliable isotopic identification for a number of ^194 Ir lines. The multipolarity admixtures for 29 gamma-transitions were determined on the basis of conversion lines from different electron subshells. Prompt and delayed gamma-gamma coincidences were measured using semiconductor and scintillation detectors. The ^193 Ir(d,p) high-resolution spectra, observed with a magnetic spectrometer, are given. All these data contributed to establishing a detailed level scheme of ^194 Ir. Additional data and the interpretation of the results in terms of current models will be presented in a forthcoming paper
Engineering of quantum dot photon sources via electro-elastic fields
The possibility to generate and manipulate non-classical light using the
tools of mature semiconductor technology carries great promise for the
implementation of quantum communication science. This is indeed one of the main
driving forces behind ongoing research on the study of semiconductor quantum
dots. Often referred to as artificial atoms, quantum dots can generate single
and entangled photons on demand and, unlike their natural counterpart, can be
easily integrated into well-established optoelectronic devices. However, the
inherent random nature of the quantum dot growth processes results in a lack of
control of their emission properties. This represents a major roadblock towards
the exploitation of these quantum emitters in the foreseen applications. This
chapter describes a novel class of quantum dot devices that uses the combined
action of strain and electric fields to reshape the emission properties of
single quantum dots. The resulting electro-elastic fields allow for control of
emission and binding energies, charge states, and energy level splittings and
are suitable to correct for the quantum dot structural asymmetries that usually
prevent these semiconductor nanostructures from emitting polarization-entangled
photons. Key experiments in this field are presented and future directions are
discussed.Comment: to appear as a book chapter in a compilation "Engineering the
Atom-Photon Interaction" published by Springer in 2015, edited by A.
Predojevic and M. W. Mitchel
Proučavanje 194Ir uhvatom termičkih neutrona I (d, p) reakcijom
Levels of 194Ir were studied using thermal neutron capture reaction. A pair spectrometer was used to measure the high-energy γ-ray spectrum from thermal-neutron capture in enriched 193Ir target over the energy range 4640 - 6100 keV. The low-energy γ-radiation from the reaction was studied with crystal diffraction spectrometers, and conversion electrons were observed with magnetic spectrometers. The high-sensitivity measurements at the Grenoble reactor, evaluated for transition energies up to 500 keV, are compared with lower-sensitivity measurements at the Wuerenlingen and Salaspils reactors. The comparison helped to obtain reliable isotopic identification for a number of 194Ir lines. The multipolarity admixtures for 29 γ-transitions were determined on the basis of conversion lines from different electron subshells. Prompt and delayed γ-γ coincidences were measured using semiconductor and scintillation detectors. The 193Ir(d,p) high-resolution spectra, observed with a magnetic spectrometer, are given. All these data contributed to establishing a detailed level scheme of 194Ir. Additional data and the interpretation of the results in terms of current models will be presented in a forthcoming paper.Proučavala su se stanja u 194Ir reakcijama 193Ir(n, γ) i 193Ir(d, p). Mjerenja uhvata termičkih neutrona načinjena su uz reaktore u Grenoblu, Wuerenlingenu i Salapsisu. Za mjerenja γ-zračenja visoke energije upotrebljavao se spektrometar parova, a za niske energije difraktometar. Konverzijske elektrone se mjerilo magnetskim spektrometrom. Mjerenja reakcije (d, p) visokog razlučivanja izvedena su magnetskim spektrometrom. Usporedbe tih mjerenja omogućile su pouzdano izotopno prepoznavanje prijelaza u 194 Ir, a spektri konverzijskih elektrona i određivanje multipolnosti prijelaza. Dobiveni su podaci osnova sheme raspada 194Ir
X-ray two-photon absorption with high fluence XFEL pulses
We report on nonlinear interaction of solid Fe with intense femtosecond hard x-ray free-electron laser (XFEL) pulses. The experiment was performed at the CXI end- station of the Linac Coherent Light Source (LCLS) by means of high- resolution x-ray emission spectroscopy. The focused x-ray beam provided extreme fluence of ~10⁵ photons/Ų. Two-photon absorption leading to K-shell hollow atom formation and to single K-shell ionization of solid Fe was investigated
Cavity Enhancement of Single Quantum Dot Emission in the Blue
Cavity-enhanced single-photon emission in the blue spectral region was measured from single InGaN/GaN quantum dots. The low-Q microcavities used were characterized using micro-reflectance spectroscopy where the source was the enhanced blue output from a photonic crystal fibre. Micro-photoluminescence was observed from several cavities and found to be ~10 times stronger than typical InGaN quantum dot emission without a cavity. The measurements were performed using non-linear excitation spectroscopy in order to suppress the background emission from the underlying wetting layer
The HEV Ventilator
HEV is a low-cost, versatile, high-quality ventilator, which has been
designed in response to the COVID-19 pandemic. The ventilator is intended to be
used both in and out of hospital intensive care units, and for both invasive
and non-invasive ventilation. The hardware can be complemented with an external
turbine for use in regions where compressed air supplies are not reliably
available. The standard modes provided include PC-A/C(Pressure Assist
Control),PC-A/C-PRVC(Pressure Regulated Volume Control), PC-PSV (Pressure
Support Ventilation) and CPAP (Continuous Positive airway pressure). HEV is
designed to support remote training and post market surveillance via a web
interface and data logging to complement the standard touch screen operation,
making it suitable for a wide range of geographical deployment. The HEV design
places emphasis on the quality of the pressure curves and the reactivity of the
trigger, delivering a global performance which will be applicable to ventilator
needs beyond theCOVID-19 pandemic. This article describes the conceptual design
and presents the prototype units together with their performance evaluation.Comment: 34 pages, 18 figures, Extended version of the article submitted to
PNA
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