Proposal for demonstrating the Hong-Ou-Mandel effect with matter waves

The Hong-Ou-Mandel (HOM) effect is a striking demonstration of destructive quantum interference between pairs of indistinguishable bosons, realised so far only with massless photons. Here we propose an experiment which can realise this effect in the matter-wave regime using pair-correlated atoms produced via a collision of two Bose-Einstein condensates and subjected to two laser induced Bragg pulses. We formulate a novel measurement protocol appropriate for the multimode matter-wave field, which---unlike the typical two-mode optical case---bypasses the need for repeated measurements under different displacement settings of the beam-splitter, thus dramatically reducing the number of experimental runs required to map out the interference visibility. The protocol can be utilised in related matter-wave schemes; here we focus on condensate collisions and by simulating the entire experiment we predict a HOM-dip visibility of ~69%. By being larger than 50%, such a visibility highlights strong quantum correlations between the atoms and paves the way for a possible demonstration of a Bell inequality violation with massive particles in a related Rarity-Tapster setup.Comment: Essentially the same version as v2, except in Nature Communications style; for Supplementary Information see the source fil

Properties of non-stoichiometric metallic carbides final report

Nonstoichiometric transition metal carbide propertie

Space for inclusion? The Construction of Sport and Leisure Spaces as Places for Migrant Communities

The research on which this paper is based started from the proposition that sport and leisure spaces can support processes of social inclusion (Amara et al., 2005), yet may also serve to exclude certain groups. As such, these spaces may be seen as contested and racialised places that shape behaviour. We shall use this paper not just to explore how those spaces are perceived by new migrants, but how those interpretations may vary with time and processes of social change. That involves examining how sport and leisure spaces are encoded in different ways, thereby affecting people’s experience, while at the same time recognising that their sport and leisure practices shape those social constructions. We argue that such an understanding is necessary to inform policies and practices that could promote the development of mutual and shared spaces rather than disconnected multiple occupations of spaces. Our goal is not only to contribute to the development of theory, but also to the debate that has counterposed multiculturalism and integrationism. Our recent systematic review, conducted for Sporting Equals and the sports councils (Long et al., 2009), synthesised literature on participation in sport and physical recreation by people from Black and Minority Ethnic Communities (BME) in the UK. That review identified a growing body of research, but one focussing primarily on the experiences of Black and Asian groupings. That has led us to turn to a consideration of new migrant communities. In this paper we shall be reporting on empirical research conducted with ‘new migrants’ now living in Leeds

Voice control of the space shuttle video system

A pilot voice control system developed at the Jet Propulsion Laboratory (JPL) to test and evaluate the feasibility of controlling the shuttle TV cameras and monitors by voice commands utilizes a commercially available discrete word speech recognizer which can be trained to the individual utterances of each operator. Successful ground tests were conducted using a simulated full-scale space shuttle manipulator. The test configuration involved the berthing, maneuvering and deploying a simulated science payload in the shuttle bay. The handling task typically required 15 to 20 minutes and 60 to 80 commands to 4 TV cameras and 2 TV monitors. The best test runs show 96 to 100 percent voice recognition accuracy

Pattern formation by lateral inhibition with feedback: a mathematical model of Delta-Notch intercellular signalling

In many developing tissues, adjacent cells diverge in character so as to create a fine-grained pattern of cells in contrasting states of differentiation. It has been proposed that such patterns can be generated through lateral inhibition—a type cells–cell interaction whereby a cell that adopts a particular fate inhibits its immediate neighbours from doing likewise. Lateral inhibition is well documented in flies, worms and vertebrates. In all of these organisms, the transmembrane proteins Notch and Delta (or their homologues) have been identified as mediators of the interaction—Notch as receptor, Delta as its ligand on adjacent cells. However, it is not clear under precisely what conditions the Delta-Notch mechanism of lateral inhibition can generate the observed types of pattern, or indeed whether this mechanism is capable of generating such patterns by itself. Here we construct and analyse a simple and general mathematical model of such contact-mediated lateral inhibition. In accordance with experimental data, the model postulates that receipt of inhibition (i.e. activation of Notch) diminishes the ability to deliver inhibition (i.e. to produce active Delta). This gives rise to a feedback loop that can amplify differences between adjacent cells. We investigate the pattern-forming potential and temporal behavior of this model both analytically and through numerical simulation. Inhomogeneities are self-amplifying and develop without need of any other machinery, provided the feedback is sufficiently strong. For a wide range of initial and boundary conditions, the model generates fine-grained patterns similar to those observed in living systems