Experimental demonstration of continuous variable purification of squeezed states

We report on the first experimental demonstration of purification of nonclassical continuous variable states. The protocol uses two copies of phase-diffused states overlapped on a beam splitter and provides Gaussified, less mixed states with the degree of squeezing improved. The protocol uses only linear optical devices such as beam splitters and homodyne detection, thereby proving these optical elements can be used for successful purification of this type of state decoherence which occurs in optical transmission channels

Preparing the bound instance of quantum entanglement

Among the possibly most intriguing aspects of quantum entanglement is that it comes in "free" and "bound" instances. Bound entangled states require entangled states in preparation but, once realized, no free entanglement and therefore no pure maximally entangled pairs can be regained. Their existence hence certifies an intrinsic irreversibility of entanglement in nature and suggests a connection with thermodynamics. In this work, we present a first experimental unconditional preparation and detection of a bound entangled state of light. We consider continuous-variable entanglement, use convex optimization to identify regimes rendering its bound character well certifiable, and realize an experiment that continuously produced a distributed bound entangled state with an extraordinary and unprecedented significance of more than ten standard deviations away from both separability and distillability. Our results show that the approach chosen allows for the efficient and precise preparation of multimode entangled states of light with various applications in quantum information, quantum state engineering and high precision metrology.Comment: The final version accounts for a recent comment in Nature Physics [24] clarifying that a previous claim of having generated bound entanglement [23] was not supported by the authors' data. We also extended our introduction and discussion and also added reference

High Rayleigh number convection with double diffusive fingers

An electrodeposition cell is used to sustain a destabilizing concentration difference of copper ions in aqueous solution between the top and bottom boundaries of the cell. The resulting convecting motion is analogous to Rayleigh-B\'enard convection at high Prandtl numbers. In addition, a stabilizing temperature gradient is imposed across the cell. Even for thermal buoyancy two orders of magnitude smaller than chemical buoyancy, the presence of the weak stabilizing gradient has a profound effect on the convection pattern. Double diffusive fingers appear in all cases. The size of these fingers and the flow velocities are independent of the height of the cell, but they depend on the ion concentration difference between top and bottom boundaries as well as on the imposed temperature gradient. The scaling of the mass transport is compatible with previous results on double diffusive convection

A simulation model for probabilistic analysis of Space Shuttle abort modes

A simulation model which was developed to provide a probabilistic analysis tool to study the various space transportation system abort mode situations is presented. The simulation model is based on Monte Carlo simulation of an event-tree diagram which accounts for events during the space transportation system's ascent and its abort modes. The simulation model considers just the propulsion elements of the shuttle system (i.e., external tank, main engines, and solid boosters). The model was developed to provide a better understanding of the probability of occurrence and successful completion of abort modes during the vehicle's ascent. The results of the simulation runs discussed are for demonstration purposes only, they are not official NASA probability estimates

Towards Einstein-Podolsky-Rosen quantum channel multiplexing

A single broadband squeezed field constitutes a quantum communication resource that is sufficient for the realization of a large number N of quantum channels based on distributed Einstein-Podolsky-Rosen (EPR) entangled states. Each channel can serve as a resource for, e.g. independent quantum key distribution or teleportation protocols. N-fold channel multiplexing can be realized by accessing 2N squeezed modes at different Fourier frequencies. We report on the experimental implementation of the N=1 case through the interference of two squeezed states, extracted from a single broadband squeezed field, and demonstrate all techniques required for multiplexing (N>1). Quantum channel frequency multiplexing can be used to optimize the exploitation of a broadband squeezed field in a quantum information task. For instance, it is useful if the bandwidth of the squeezed field is larger than the bandwidth of the homodyne detectors. This is currently a typical situation in many experiments with squeezed and two-mode squeezed entangled light.Comment: 4 pages, 4 figures. In the new version we cite recent experimental work bei Mehmet et al., arxiv0909.5386, in order to clarify the motivation of our work and its possible applicatio

Investment in Human Capital of a Powerful Interest Group: The Case of the Medical Profession in Britain, France, Sweden and the United States from 1890 to 1970

This paper presents a new agenda for analyzing the consequences from investments in human capital by suggesting that sociological research should focus on particular sectors of society, that performances other than economic growth and productivity should be considered, and that the role of the state influences the impact which investments in human capital have on system performance. The research assesses the impact which investments in doctors and medical specialists have on social effectiveness (measured as reductions in mortality) and social efficiency (the level of health achieved relative to the cost per capita) in Britain, France, Sweden and the United States during the period between 1890 and 1970. In addition to evaluating the impact of investments in human capital on social efficiency and social effectiveness, the paper contributes to the literature on the state by developing measures for assessing the contribution of state structure on system performance. As hypothesized, investments in human capital are socially effective but not socially efficient. When the state intervenes in the delivery of medical care, it has a multiplier effect on the impact of human capital on social effectiveness.Dieses Papier stellt einen neuen Anlauf zur Analyse der Konsequenzen von Investitionen in Humankapital dar, indem es vorschlägt, sich in der Forschung auf spezifische Gesellschaftsbereiche zu konzentrieren, daß Leistungsmaße jenseits ökonomischen Wachstums und ökonomischer Produktivität Berücksichtigung finden. Auch der intervenierende Einfluß des Staates auf die Wirkungen, welche Investitionen in Humankapital auf die Leistungsfähigkeiten des Systems haben, sollte berücksichtigt werden. Die in diesem Aufsatz dargestellte Forschung schätzt die Wirkungen ab, welche Investitionen in Ärzte und medizinische Spezialisten auf die soziale Effektivität (gemessen als Verminderung von Sterblichkeit) und soziale Effizienz (das Gesundheitsniveau im Verhältnis zu den Gesundheitskosten per Einwohner) in Großbritannien, Frankreich, Schweden und den Vereinigten Staaten während des Zeitraums von 1890 bis 1970 hatten. Über diese Evaluation hinaus ist der Aufsatz ein Beitrag zur staatstheoretischen Literatur, indem er Maße entwickelt, mit denen die Wirkung staatlicher Strukturen auf die Leistungsfähigkeit spezifischer Systeme abgeschätzt werden können. Investitionen in Humankapital erweisen sich als sozial effektiv aber nicht effizient. Immer dann, wenn der Staat in das System medizinischer Dienstleistungen eingreift, hat dies einen Multiplikationseffekt hinsichtlich des Einflusses von Humankapital auf soziale Effektivität.1. Introduction 2. Theoretical Framework 2.1 Human Capital and Social Effectiveness 2.2 Human Capital and Social Efficiency 2.3 Physicians-, the State, and Social Performances 3. Research Design, Data, and Methodology 3.1 The Dependent Variables: Social Effectiveness and Social Efficiency 3.2 The Independent Variables 3.3 Data 3.4 Data Analytic Techniques 4. Findings 4.1 Trends in Mortality and Social Efficiency 4.2 Human Capital Investment and Social Effectiveness 4.3 Human Capital Investment and Social Efficiency 5. Discussion Appendix: Data Sources Bibliograph

Phylogenetic reorganization of the basal ganglia: A necessary, but not the only, bridge over a primate Rubicon of acoustic communication

In this response to commentaries, we revisit the two main arguments of our target article. Based on data drawn from a variety of research areas – vocal behavior in nonhuman primates, speech physiology and pathology, neurobiology of basal ganglia functions, motor skill learning, paleoanthropological concepts – the target article, first, suggests a two-stage model of the evolution of the crucial motor prerequisites of spoken language within the hominin lineage: (1) monosynaptic refinement of the projections of motor cortex to brainstem nuclei steering laryngeal muscles, and (2) subsequent “vocal-laryngeal elaboration” of cortico-basal ganglia circuits, driven by human-specific FOXP2 mutations. Second, as concerns the ontogenetic development of verbal communication, age-dependent interactions between the basal ganglia and their cortical targets are assumed to contribute to the time course of the acquisition of articulate speech. Whereas such a phylogenetic reorganization of cortico-striatal circuits must be considered a necessary prerequisite for ontogenetic speech acquisition, the 30 commentaries – addressing the whole range of data sources referred to – point at several further aspects of acoustic communication which have to be added to or integrated with the presented model. For example, the relationships between vocal tract movement sequencing – the focus of the target article – and rhythmical structures of movement organization, the connections between speech motor control and the central-auditory and central-visual systems, the impact of social factors upon the development of vocal behavior (in nonhuman primates and in our species), and the interactions of ontogenetic speech acquisition – based upon FOXP2-driven structural changes at the level of the basal ganglia – with preceding subvocal stages of acoustic communication as well as higher-order (cognitive) dimensions of phonological development. Most importantly, thus, several promising future research directions unfold from these contributions – accessible to clinical studies and functional imaging in our species as well as experimental investigations in nonhuman primates

Photometry of supernovae in an image series : methods and application to the Supernova Legacy Survey (SNLS)

We present a technique to measure lightcurves of time-variable point sources on a spatially structured background from imaging data. The technique was developed to measure light curves of SNLS supernovae in order to infer their distances. This photometry technique performs simultaneous PSF photometry at the same sky position on an image series. We describe two implementations of the method: one that resamples images before measuring fluxes, and one which does not. In both instances, we sketch the key algorithms involved and present the validation using semi-artificial sources introduced in real images in order to assess the accuracy of the supernova flux measurements relative to that of surrounding stars. We describe the methods required to anchor these PSF fluxes to calibrated aperture catalogs, in order to derive SN magnitudes. We find a marginally significant bias of 2 mmag of the after-resampling method, and no bias at the mmag accuracy for the non-resampling method. Given surrounding star magnitudes, we determine the systematic uncertainty of SN magnitudes to be less than 1.5 mmag, which represents about one third of the current photometric calibration uncertainty affecting SN measurements. The SN photometry delivers several by-products: bright star PSF flux mea- surements which have a repeatability of about 0.6%, as for aperture measurements; we measure relative astrometric positions with a noise floor of 2.4 mas for a single-image bright star measurement; we show that in all bands of the MegaCam instrument, stars exhibit a profile linearly broadening with flux by about 0.5% over the whole brightness range.Comment: Accepted for publication in A&A. 20 page