An integrated source of broadband quadrature squeezed light

An integrated silicon nitride resonator is proposed as an ultra-compact source of bright single-mode quadrature squeezed light at 850 nm. Optical properties of the device are investigated and tailored through numerical simulations, with particular attention paid to loss associated with interfacing the device. An asymmetric double layer stack waveguide geometry with inverse vertical tapers is proposed for efficient and robust fibre-chip coupling, yielding a simulated total loss of -0.75 dB/facet. We assess the feasibility of the device through a full quantum noise analysis and derive the output squeezing spectrum for intra-cavity pump self-phase modulation. Subject to standard material loss and detection efficiencies, we find that the device holds promises for generating substantial quantum noise squeezing over a bandwidth exceeding 1 GHz. In the low-propagation loss regime, approximately -7 dB squeezing is predicted for a pump power of only 50 mW.Comment: 23 pages, 12 figure

The chemistry of ZnWO₄ nanoparticle formation

The need for a change away from classical nucleation and growth models for the description of nanoparticle formation is highlighted. By the use of in situ total X-ray scattering experiments the transformation of an aqueous polyoxometalate precursor mixture to crystalline ZnWO$_{4}$ nanoparticles under hydrothermal conditions was followed. The precursor solution is shown to consist of specific Tourné-type sandwich complexes. The formation of pristine ZnWO$_{4}$ within seconds is understood on the basis of local restructuring and three-dimensional reordering preceding the emergence of long range order in ZnWO$_{4}$ nanoparticles. An observed temperature dependent trend in defect concentration can be rationalized based on the proposed formation mechanism. Following nucleation the individual crystallites were found to grow into prolate morphology with elongation along the unit cell c-direction. Extensive electron microscopy characterization provided evidence for particle growth by oriented attachment; a notion supported by sudden particle size increases observed in the in situ total scattering experiments. A simple continuous hydrothermal flow method was devised to synthesize highly crystalline monoclinic zinc tungstate (ZnWO$_{4}$) nanoparticles in large scale in less than one minute. The present results highlight the profound influence of structural similarities in local structure between reactants and final materials in determining the specific nucleation of nanostructures and thus explains the potential success of a given synthesis procedure in producing nanocrystals. It demonstrates the need for abolishing outdated nucleation models, which ignore subtle yet highly important system dependent differences in the chemistry of the forming nanocrystals

Ab-initio Quantum Enhanced Optical Phase Estimation Using Real-time Feedback Control

Optical phase estimation is a vital measurement primitive that is used to perform accurate measurements of various physical quantities like length, velocity and displacements. The precision of such measurements can be largely enhanced by the use of entangled or squeezed states of light as demonstrated in a variety of different optical systems. Most of these accounts however deal with the measurement of a very small shift of an already known phase, which is in stark contrast to ab-initio phase estimation where the initial phase is unknown. Here we report on the realization of a quantum enhanced and fully deterministic phase estimation protocol based on real-time feedback control. Using robust squeezed states of light combined with a real-time Bayesian estimation feedback algorithm, we demonstrate deterministic phase estimation with a precision beyond the quantum shot noise limit. The demonstrated protocol opens up new opportunities for quantum microscopy, quantum metrology and quantum information processing.Comment: 5 figure

L’utilisation des réseaux sociaux (Snapchat, WhatsApp et Instagram) et le cyberbullying

100% des jeunes possèdent un téléphone portable, 99% ont un ordinateur et 97% ont accès à Internet (Waller et al., 2016). Ces nouveaux moyens technologiques font partie de notre quotidien. Depuis l’apparition de ces réseaux, un nouveau mouvement est né : le cyberbullying. Ce harcèlement par Internet consiste à l’utilisation de technologies modernes de communication afin de nuire aux autres de manière délibérée et agressive. Quand les jeunes arrivent en classe, ils apportent avec eux l’entier de leur vécu quotidien, familial ou encore émotionnel. Les problèmes liés à l’utilisation massive de ces réseaux font partie de notre quotidien d’enseignant. Malheureusement, les études faites jusqu’au jour d’aujourd’hui portent en majeure partie sur les élèves entre 13 ans et plus. Mais qu’en est-il des jeunes âgés entre 9 et 12 ans ? Notre travail de recherche porte donc sur l’utilisation des réseaux sociaux (Snapchat, Instagram et WhatsApp) et le cyberbullying. Deux outils différents ont été utilisés lors de cette recherche : des questionnaires afin d’avoir des résultats quantitatifs et deux entretiens afin d’avoir un point de vue qualitatif. Nos résultats montrent que WhatsApp est le réseau social le plus utilisé, suivi d’Instagram en deuxième position et finalement de Snapchat. Les élèves considèrent le nombre de dangers et de conflits sur les réseaux comme très faibles. Ils avouent tout de même donner plus d’informations personnelles sur WhatsApp que sur les autres réseaux choisis dans l’étude. Concernant leur vision du contrôle des parents, ils l’estiment très faible. Cependant, il s’agit uniquement de leur avis, il serait intéressant de savoir la réalité des faits en interrogeant les parents. Les deux sujets interrogés savent définir le cyberbullying et connaissent les différents acteurs agissant au sein de cette forme de harcèlement. Ils sont également conscients des différents risques, conséquences ou sentiments que peut ressentir une cyber-victime mais n’abordent pas du tout ceux concernant le témoin ou le cyber-harceleur. En conclusion, notre recherche montre que les réseaux sociaux font partie intégrante du quotidien d’un grand nombre d’élèves. Il est donc essentiel que les enseignants s’interrogent sur les moyens de gérer les problèmes que ceux-ci peuvent amener en classe mais également les moyens de les éviter

The effectiveness of neuromuscular warm-up strategies, that require no additional equipment, for preventing lower limb injuries during sports participation: a systematic review

PMCID: PMC3408383The electronic version of this article is the complete one and can be found online at: http://www.biomedcentral.com/1741-7015/10/75. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

Comparison of Short-Term Estrogenicity Tests for Identification of Hormone-Disrupting Chemicals

The aim of this study was to compare results obtained by eight different short-term assays of estrogenlike actions of chemicals conducted in 10 different laboratories in five countries. Twenty chemicals were selected to represent direct-acting estrogens, compounds with estrogenic metabolites, estrogenic antagonists, and a known cytotoxic agent. Also included in the test panel were 17β-estradiol as a positive control and ethanol as solvent control. The test compounds were coded before distribution. Test methods included direct binding to the estrogen receptor (ER), proliferation of MCF-7 cells, transient reporter gene expression in MCF-7 cells, reporter gene expression in yeast strains stably transfected with the human ER and an estrogen-responsive reporter gene, and vitellogenin production in juvenile rainbow trout. 17β-Estradiol, 17α-ethynyl estradiol, and diethylstilbestrol induced a strong estrogenic response in all test systems. Colchicine caused cytotoxicity only. Bisphenol A induced an estrogenic response in all assays. The results obtained for the remaining test compounds—tamoxifen, ICI 182.780, testosterone, bisphenol A dimethacrylate, 4-n-octylphenol, 4-n-nonylphenol, nonylphenol dodecylethoxylate, butylbenzylphthalate, dibutylphthalate, methoxychlor, o,p′-DDT, p,p′-DDE, endosulfan, chlomequat chloride, and ethanol—varied among the assays. The results demonstrate that careful standardization is necessary to obtain a reasonable degree of reproducibility. Also, similar methods vary in their sensitivity to estrogenic compounds. Thus, short-term tests are useful for screening purposes, but the methods must be further validated by additional interlaboratory and interassay comparisons to document the reliability of the methods

Quantum-enhanced micromechanical displacement sensitivity

We report on a hitherto unexplored application of squeezed light: for quantum-enhancement of mechanical transduction sensitivity in microcavity optomechanics. Using a toroidal silica microcavity, we experimentally demonstrate measurement of the transduced phase modulation signal with a sensitivity $-0.72(\pm 0.01)$\,dB below the shot noise level. This is achieved for resonant probing in the highly under-coupled regime, by preparing the probe in a weak coherent state with phase squeezed vacuum states at sideband frequencies