618 research outputs found
Highly nonclassical photon statistics in parametric down conversion
We use photon counters to obtain the joint photon counting statistics from
twin-beam non-degenerate parametric down conversion, and we demonstrate
directly, and with no auxiliary assumptions, that these twin beams are
nonclassical
Application of photogrammetry techniques for the visual assessment of vessels' cargo hold
Visual inspection is an integral part of Condition and Class surveys, with the results comprising of the surveyors’ opinion, documented by a sum of pictures indicating areas of interest. Although this way provides the most essential information, the communication of the results may be difficult, since isolated images cannot provide the context. Photogrammetry exploits pictorial data to provide 3D models, with a high level of accuracy and is not an uncommon method in the maritime environment. Use of such methods to support visual survey activities is examined in this work, providing the methodology for the data collection, which is structured in an algorithmic way, to enable realization by automated means (robots). The 3D model is provided, along with accuracy results
Improvement of continuous-variable quantum key distribution systems by using optical preamplifiers
Continuous-variable quantum key distribution protocols, based on Gaussian
modulation of the quadratures of coherent states, have been implemented in
recent experiments. A present limitation of such systems is the finite
efficiency of the detectors, which can in principle be compensated for by the
use of classical optical preamplifiers. Here we study this possibility in
detail, by deriving the modified secret key generation rates when an optical
parametric amplifier is placed at the output of the quantum channel. After
presenting a general set of security proofs, we show that the use of
preamplifiers does compensate for all the imperfections of the detectors when
the amplifier is optimal in terms of gain and noise. Imperfect amplifiers can
also enhance the system performance, under conditions which are generally
satisfied in practice.Comment: 11 pages, 7 figures, submitted to J. Phys. B (special issue on Few
Atoms Optics
Experimental verification of multipartite entanglement in quantum networks
Multipartite entangled states are a fundamental resource for a wide range of
quantum information processing tasks. In particular, in quantum networks it is
essential for the parties involved to be able to verify if entanglement is
present before they carry out a given distributed task. Here we design and
experimentally demonstrate a protocol that allows any party in a network to
check if a source is distributing a genuinely multipartite entangled state,
even in the presence of untrusted parties. The protocol remains secure against
dishonest behaviour of the source and other parties, including the use of
system imperfections to their advantage. We demonstrate the verification
protocol in a three- and four-party setting using polarization-entangled
photons, highlighting its potential for realistic photonic quantum
communication and networking applications.Comment: 8 pages, 4 figure
Anti-androgens act jointly in suppressing spiggin concentrations in androgen-primed female three-spined sticklebacks - Prediction of combined effects by concentration addition
This is the post-print version of the final paper published in Aquatic Toxicology. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2013 Elsevier B.V.Increasing attention is being directed at the role played by anti-androgenic chemicals in endocrine disruption of wildlife within the aquatic environment. The co-occurrence of multiple contaminants with anti-androgenic activity highlights a need for the predictive assessment of combined effects, but information about anti-androgen mixture effects on wildlife is lacking. This study evaluated the suitability of the androgenised female stickleback screen (AFSS), in which inhibition of androgen-induced spiggin production provides a quantitative assessment of anti-androgenic activity, for predicting the effect of a four component mixture of anti-androgens. The anti-androgenic activity of four known anti-androgens (vinclozolin, fenitrothion, flutamide, linuron) was evaluated from individual concentration-response data and used to design a mixture containing each chemical at equipotent concentrations. Across a 100-fold concentration range, a concentration addition approach was used to predict the response of fish to the mixture. Two studies were conducted independently at each of two laboratories. By using a novel method to adjust for differences between nominal and measured concentrations, good agreement was obtained between the actual outcome of the mixture exposure and the predicted outcome. This demonstrated for the first time that androgen receptor antagonists act in concert in an additive fashion in fish and that existing mixture methodology is effective in predicting the outcome, based on concentration-response data for individual chemicals. The sensitivity range of the AFSS assay lies within the range of anti-androgenicity reported in rivers across many locations internationally. The approach taken in our study lays the foundations for understanding how androgen receptor antagonists work together in fish and is essential in informing risk assessment methods for complex anti-androgenic mixtures in the aquatic environment.European Commission and
Natural Environment Research Council
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
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