Robust quantum state engineering through coherent localization in biased-coin quantum walks

We address the performance of a coin-biased quantum walk as a generator for non-classical position states of the walker. We exploit a phenomenon of coherent localisation in the position space --- resulting from the choice of small values of the coin parameter and assisted by post-selection --- to engineer large-size coherent superpositions of distinguishable position states of the walker. The protocol that we design appears to be remarkably robust against both the actual value taken by the coin parameter and strong dephasing-like noise acting on the spatial degree of freedom. We finally illustrate a possible linear-optics implementation of our proposal, suitable for both bulk and integrated-optics platforms.Comment: 7 pages, 7 figure

P- and S- wave velocities of consolidated sediments from a seafloor seismic survey in the North Celtic Sea Basin, offshore Ireland

A geophysical survey was conducted over a hydrocarbon prospect in the North Celtic Sea Basin using a small array of ocean-bottom seismographs (OBSs). The purpose of this study was to determine the ratio of (P) compressional- to (S) shear-wave velocity of consolidated sedimentary rocks in order to constrain possible subsurface variations in pore-fluid content. The ratio of VP and VS- is known to be particularly sensitive to lithology, porosity and pore-fluid content, making it a useful parameter for evaluating hydrocarbon prospects. OBSs offer a relatively cheap and time-effective means of acquiring multi-component data compared with ocean-bottom cables. In this contribution, we demonstrate the ability of an OBS survey comprising three pairs of two OBSs spaced at 1.6 km to recover lateral variations in the VP/VS ratio. A key requirement of this type of study is that S-waves will be generated by mode conversions in the subsurface, since they cannot be generated in nor travel through fluids. In this survey, the contrast in physical properties of the hard seabed of the North Celtic Sea Basin provided a means of generating converted S-waves. Two-dimensional ray-tracing and forward modeling was used to create both VP and VS models along a profile crossing the Blackrock prospect in the North Celtic Sea Basin. These models comprise four layers and extend to a maximum depth of 1.1 km. The observed northward decrease in the VP/VS ratio at depths of 500-1000 m below the seafloor in the study area is interpreted to represent lateral variation in the amount of gas present in the pore space of Upper Cretaceous chalks and shales overlying the prospective reservoir

Colloidal, tribological and sensory properties of oral nutritional supplements

This study aims to evaluate the physicochemical and sensory properties of oral nutritional supplements (ONSs). High physical stability was measured in ONSs with mean particle sizes <0.33 !m and viscosity >19.3 mPa·s. ONSs formulated with dairy-soy protein mixtures displayed low friction coefficients, whereas ONSs containing dairy proteins alone had high friction coefficient values in the boundary regime. Sensory analysis revealed low to medium liking across the products and the highest preference was found in samples with the highest perceived 'sweetness', 'vanilla aroma' and 'thickness'. The results will underpin the formulation of novel ONSs with good physical stability and sensory acceptability

Deep Chandra Observations of HCG 16 - II. The Development of the Intra-group Medium in a Spiral-Rich Group

We use a combination of deep Chandra X-ray observations and radio continuum imaging to investigate the origin and current state of the intra-group medium in the spiral-rich compact group HCG 16. We confirm the presence of a faint ($L_{X,{\rm bolo}}$=1.87$^{+1.03}_{-0.66}$$\times$10$^{41}$ erg/s), low temperature (0.30$^{+0.07}_{-0.05}$ keV) intra-group medium (IGM) extending throughout the ACIS-S3 field of view, with a ridge linking the four original group members and extending to the southeast, as suggested by previous Rosat and XMM-Newton observations. This ridge contains 6.6$^{+3.9}_{-3.3}$$\times$10$^9$ solar masses of hot gas and is at least partly coincident with a large-scale HI tidal filament, indicating that the IGM in the inner part of the group is highly multi-phase. We present evidence that the group is not yet virialised, and show that gas has probably been transported from the starburst winds of NGC 838 and NGC 839 into the surrounding IGM. Considering the possible origin of the IGM, we argue that material ejected by galactic winds may have played a significant role, contributing 20-40% of the observed hot gas in the system.Comment: 11 pages, 6 figures, 1 table, accepted for publication in ApJ; updated references and fixed typos identified at proof stag

Deep Chandra Observations of HCG 16 - I. Active Nuclei, Star formation and Galactic Winds

We present new, deep Chandra X-ray and Giant Metrewave Radio Telescope 610~MHz observations of the spiral-galaxy-rich compact group HCG 16, which we use to examine nuclear activity, star formation and the high luminosity X-ray binary populations in the major galaxies. We confirm the presence of obscured active nuclei in NGC 833 and NGC 835, and identify a previously unrecognized nuclear source in NGC 838. All three nuclei are variable on timescales of months to years, and for NGC 833 and NGC 835 this is most likely caused by changes in accretion rate. The deep Chandra observations allow us to detect for the first time an Fe-K$\alpha$ emission line in the spectrum of the Seyfert 2 nucleus of NGC 835. We find that NGC 838 and NGC 839 are both starburst-dominated systems, with only weak nuclear activity, in agreement with previous optical studies. We estimate the star formation rates in the two galaxies from their X-ray and radio emission, and compare these results with estimates from the infra-red and ultra-violet bands to confirm that star formation in both galaxies is probably declining after galaxy-wide starbursts were triggered ~400-500 Myr ago. We examine the physical properties of their galactic superwinds, and find that both have temperatures of ~0.8 keV. We also examine the X-ray and radio properties of NGC 848, the fifth largest galaxy in the group, and show that it is dominated by emission from its starburst.Comment: 18 pages, 11 figures, 11 tables, accepted for publication in ApJ; updated references and fixed typos identified at proof stag