256 research outputs found
Provably Secure Experimental Quantum Bit-String Generation
Coin tossing is a cryptographic task in which two parties who do not trust
each other aim to generate a common random bit. Using classical communication
this is impossible, but non trivial coin tossing is possible using quantum
communication. Here we consider the case when the parties do not want to toss a
single coin, but many. This is called bit string generation. We report the
experimental generation of strings of coins which are provably more random than
achievable using classical communication. The experiment is based on the ``plug
and play'' scheme developed for quantum cryptography, and therefore well suited
for long distance quantum communication.Comment: 4 pages, 3 figures. Submitted to Phys. Rev. Lett. A complete security
analysis for the experiment is given in quant-ph/040812
Vector modulation instability induced by vacuum fluctuations in highly birefringent fibers in the anomalous dispersion regime
We report a detailed experimental study of vector modulation instability in
highly birefringent optical fibers in the anomalous dispersion regime. We prove
that the observed instability is mainly induced by vacuum fluctuations. The
detuning of the spectral peaks agrees with linear perturbation analysis. The
exact shape of the spectrum is well reproduced by numerical integration of
stochastic nonlinear Schrodinger equations describing quantum propagation.Comment: 11 pages, 4 figures, to be published in Optics Letter
Scalar and vector modulation instabilities induced by vacuum fluctuations in fibers: numerical study
We study scalar and vector modulation instabilities induced by the vacuum
fluctuations in birefringent optical fibers. To this end, stochastic coupled
nonlinear Schrodinger equations are derived. The stochastic model is equivalent
to the quantum field operators equations and allow for dispersion,
nonlinearity, and arbitrary level of birefringence. Numerical integration of
the stochastic equations is compared to analytical formulas in the case of
scalar modulation instability and non depleted pump approximation. The effect
of classical noise and its competition with vacuum fluctuations for inducing
modulation instability is also addressed.Comment: 33 pages, 5 figure
Autocorrelation analysis for the unbiased determination of power-law exponents in single-quantum-dot blinking
We present an unbiased and robust analysis method for power-law blinking
statistics in the photoluminescence of single nano-emitters, allowing us to
extract both the bright- and dark-state power-law exponents from the emitters'
intensity autocorrelation functions. As opposed to the widely-used threshold
method, our technique therefore does not require discriminating the emission
levels of bright and dark states in the experimental intensity timetraces. We
rely on the simultaneous recording of 450 emission timetraces of single
CdSe/CdS core/shell quantum dots at a frame rate of 250 Hz with single photon
sensitivity. Under these conditions, our approach can determine ON and OFF
power-law exponents with a precision of 3% from a comparison to numerical
simulations, even for shot-noise-dominated emission signals with an average
intensity below 1 photon per frame and per quantum dot. These capabilities pave
the way for the unbiased, threshold-free determination of blinking power-law
exponents at the micro-second timescale
SST-GATE: A dual mirror telescope for the Cherenkov Telescope Array
The Cherenkov Telescope Array (CTA) will be the world's first open
observatory for very high energy gamma-rays. Around a hundred telescopes of
different sizes will be used to detect the Cherenkov light that results from
gamma-ray induced air showers in the atmosphere. Amongst them, a large number
of Small Size Telescopes (SST), with a diameter of about 4 m, will assure an
unprecedented coverage of the high energy end of the electromagnetic spectrum
(above ~1TeV to beyond 100 TeV) and will open up a new window on the
non-thermal sky. Several concepts for the SST design are currently being
investigated with the aim of combining a large field of view (~9 degrees) with
a good resolution of the shower images, as well as minimizing costs. These
include a Davies-Cotton configuration with a Geiger-mode avalanche photodiode
(GAPD) based camera, as pioneered by FACT, and a novel and as yet untested
design based on the Schwarzschild-Couder configuration, which uses a secondary
mirror to reduce the plate-scale and to allow for a wide field of view with a
light-weight camera, e.g. using GAPDs or multi-anode photomultipliers. One
objective of the GATE (Gamma-ray Telescope Elements) programme is to build one
of the first Schwarzschild-Couder prototypes and to evaluate its performance.
The construction of the SST-GATE prototype on the campus of the Paris
Observatory in Meudon is under way. We report on the current status of the
project and provide details of the opto-mechanical design of the prototype, the
development of its control software, and simulations of its expected
performance.Comment: In Proceedings of the 33rd International Cosmic Ray Conference
(ICRC2013), Rio de Janeiro (Brazil). All CTA contributions at arXiv:1307.223
The need of support in communities using EcoSan latrine products in farming for safe practices
A cross sectional mixed method study was conducted in Burera District, one of the pioneer districts in Rwanda using EcoSan latrines and their products in farming, to assess the practice for community health safety. This research involved household interviews and observations, key informants interviews and focus group discussion as data collection methods. The results showed a high appreciation of the use of EcoSan latrine and products for both proper sanitation suitable for the volcanic area and farming as well among study communities. However, the communities aren’t well informed about health risks related to the handling of EcoSan latrine products and this situation coupled with the lack of standard operation procedures and guidelines at community level, explains the noted inconsistency in stabilisation, handling, application of the faeces and urine in farming to prevent potential health risks
Fluorescent oxide nanoparticles adapted to active tips for near-field optics
We present a new kind of fluorescent oxide nanoparticles with properties well
suited to active-tip based near-field optics. These particles with an average
diameter in the range 5-10 nm are produced by Low Energy Cluster Beam
Deposition (LECBD) from a YAG:Ce3+ target. They are studied by transmission
electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), classical
photoluminescence, cathodoluminescence and near-field scanning optical
microscopy (NSOM). Particles of extreme photo-stability as small as 10 nm in
size are observed. These emitters are validated as building blocks of active
NSOM tips by coating a standard optical tip with a 10 nm thick layer of
YAG:Ce3+ particles directly in the LECBD reactor and by subsequently performing
NSOM imaging of test surfaces.Comment: Changes made following Referee's comments; added references; one
added figure. See story on this article at:
http://nanotechweb.org/cws/article/tech/3606
Report drawn up on behalf of the Committee on Economic and Monetary Affairs on the proposal from the Commission of the European Communities to the Council (Doc. 1-99/83-COM(83) 85 final) for a Council Decision implementing the decision empowering the Commission to borrow under the New Community Instrument for the purpose of promoting investment within the Community, Working Documents 1983-1984, Document 1-236/83, 3 May 1983
The 4MOST([1]) instrument is a concept for a wide-field, fibre-fed high multiplex spectroscopic instrument facility on the ESO VISTA telescope designed to perform a massive (initially >25x10(6) spectra in 5 years) combined all-sky public survey. The main science drivers are: Gaia follow up of chemo-dynamical structure of the Milky Way, stellar radial velocities, parameters and abundances, chemical tagging; eROSITA follow up of cosmology with x-ray clusters of galaxies, X-ray AGN/galaxy evolution to z similar to 5, Galactic X-ray sources and resolving the Galactic edge; Euclid/LSST/SKA and other survey follow up of Dark Energy, Galaxy evolution and transients. The surveys will be undertaken simultaneously requiring: highly advanced targeting and scheduling software, also comprehensive data reduction and analysis tools to produce high-level data products. The instrument will allow simultaneous observations of similar to 1600 targets at R similar to 5,000 from 390-900nm and similar to 800 targets at R>18,000 in three channels between similar to 395-675nm (channel bandwidth: 45nm blue, 57nm green and 69nm red) over a hexagonal field of view of similar to 4.1 degrees2. The initial 5-year 4MOST survey is currently expect to start in 2020. We provide and overview of the 4MOST systems: opto-mechanical, control, data management and operations concepts; and initial performance estimates
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