Experimental observation of four-photon entanglement from down-conversion

We observe polarization-entanglement between four photons produced from a single down-conversion source. The non-classical correlations between the measurement results violate a generalized Bell inequality for four qubits. The characteristic properties and its easy generation with high interferometric contrast make the observed four-photon state well-suited for implementing advanced quantum communication schemes such as multi-party quantum key distribution, secret sharing and telecloning.Comment: 4 pages, 3 figure

Radiological anatomy of the ambient cistern in children

Ambient cistern (AC) is a thin extension of the subarachnoid space surrounding the brainstem at the level of the mesencephalon and pons. Despite various definitions, it constitutes an important landmark in clinical assessment of intracranial volume reserve. Although it is indisputably useful, there exists no defined standard for radiological examination for the dimensions and ranges in specific age groups. This paper aims to describe the ambient cistern anatomically and give the ranges of dimensions for proper radiological interpretation. The study was performed on 160 axial computed tomography (CT) examinations of Polish children of both sexes, aged 1-18 years, admitted to the hospital because of mild brain concussion. Pictures were made using a Siemens 8-row CT scanner, without contrast administration. We estimated distances at the level of the pons and midbrain, based on axial cross-sections, according to standard radiological protocol. The parameters included the width of the AC in its anterior and posterior part, the width of the tentorial notch, and the distance from the pons and sella. All measurements were analyzed statistically with StatSoft Statistica 8.0 software. The average width of the AC differs between age groups. It is greatest at 1-3 years (2.8 ± 0.6 mm) and lowest at 4-10 years (2.4 ± 0.6 mm). AC is more likely to be greater in its anterior part in boys. The distance from the sella to the pons is greatest in 1-3-year-old girls (6.9 ± 1.3 mm), and the tentorial notch is widest in the 15-18-year-old group (24.6 ± 2.4 mm). Dimensions of the AC correlate with intracranial reserve volume. This is particularly visible in the youngest children. Thin and narrow AC is not always a sign of raised intracranial pressure. It may be specific for the child’s age. (Folia Morphol 2010; 69, 2: 78-83

Decoherence-Free Quantum Information Processing with Four-Photon Entangled States

Decoherence-free states protect quantum information from collective noise, the predominant cause of decoherence in current implementations of quantum communication and computation. Here we demonstrate that spontaneous parametric down-conversion can be used to generate four-photon states which enable the encoding of one qubit in a decoherence-free subspace. The immunity against noise is verified by quantum state tomography of the encoded qubit. We show that particular states of the encoded qubit can be distinguished by local measurements on the four photons only.Comment: 4 pages, 4 eps figures, revtex

Sorption competition and kinetics of trivalent cations (Eu, Y and Cm) on corundum (alpha-Al2O3 ) : A batch sorption and TRLFS study

Abstract In this study we have combined batch sorption and laser spectroscopic investigations to study the sorption of Eu(III) and Cm(III), on the aluminum oxide corundum in single- and multi-metal systems. Experiments were performed using a constant equilibrium time as a function of pH (pH-edges) or at constant pH as a function of equilibrium time (kinetic experiments) in 0.01 M NaClO4 and carbonate free conditions. The objective was to investigate how the sorption behavior of trivalent actinides and lanthanides is affected by the presence of another trivalent metal, Y(III). Our hypothesis was that the addition of higher concentrations of trivalent Y(III) together with a chemically similar trivalent metal, Eu(III) or Cm(III), would affect the sorption behavior of that metal. Batch experiments show that when the concentration of competing Y(III) is high enough (1 × 10−4 M) to occupy most of the surface sites, there is a clear shift in the position of the Eu(III) pH-edge to higher pH. Spectroscopic studies using time-resolved laser fluorescence spectroscopy (TRLFS) clearly confirm sorption competition between the trivalent metals Cm(III) and Y(III), but they also indicate a change in the surface speciation of the trivalent actinide in the presence of the competing metal if the concentration of that competing metal is high enough.Peer reviewe

The effect of relationship status on communicating emotions through touch

Research into emotional communication to date has largely focused on facial and vocal expressions. In contrast, recent studies by Hertenstein, Keltner, App, Bulleit, and Jaskolka (2006) and Hertenstein, Holmes, McCullough, and Keltner (2009) exploring nonverbal communication of emotion discovered that people could identify anger, disgust, fear, gratitude, happiness, love, sadness and sympathy from the experience of being touched on either the arm or body by a stranger, without seeing the touch. The study showed that strangers were unable to communicate the self-focused emotions embarrassment, envy and pride, or the universal emotion surprise. Literature relating to touch indicates that the interpretation of a tactile experience is significantly influenced by the relationship between the touchers (Coan, Schaefer, & Davidson, 2006). The present study compared the ability of romantic couples and strangers to communicate emotions solely via touch. Results showed that both strangers and romantic couples were able to communicate universal and prosocial emotions, whereas only romantic couples were able to communicate the self-focused emotions envy and pride

The positive impact of agile retrospectives on the collaboration of distributed development teams – A practical approach on the example of Bosch engineering GmbH

To counteract competitive pressure, increasing customer requirements and growing product complexity successful distributed collaboration in product development is vital. Companies have to face new challenges, such as efficiency losses in communication. To overcome these challenges agile working practices, such as agile retrospectives, could be beneficial. The objective of this scientific work is to evaluate the benefit of agile working practices on the example of agile retrospectives, for the improvement of collaboration in distributed development teams. Based on literature analysis, qualitative and quantitative expert interviews following the DRM by Blessing and Chakrabarti, this scientific work shows that agile working practices have a high potential to improve distributed collaboration. To address this potential, several virtual agile retrospectives are developed and conducted within a distributed team at Bosch Engineering GmbH. The evaluation of this approach results in a high potential of agile retrospectives indicating an improvement tendency. Especially iteratively implemented virtual agile retrospectives have a positive impact on successful distributed collaboration