2,794 research outputs found

    Identical Particle Scattering From A Weakly Coupled Bose-Einstein Condensed Gas

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    We calculate the scattering states and cross sections for a Bose-Einstein condensed dilute gas trapped in a spherical square well of finite depth. The interactions are treated in the scattering length approximation. We solve the Gross-Pitaevskii equation and the Bogoliubov equations for bound and scattering states. The results show that there are transparency effects reminiscent of those conjectured to occur for strongly coupled systems. When incident particle wavelengths λ are comparable to the well size a, exchange induced transparency enhancement is dramatic only for particular combinations of well depth, interaction strength, and particle number. For particles with large momenta (a/λ≫1),however, exchange with the condensate results in enhanced transmission for all coupling strengths. We calculated the rate of decay of the scattering states to leading order in anharmonic corrections to the Bogoliubov approximation and found the corresponding inelastic cross sections to be extremely small

    Targeted, structured text messaging to improve dietary and lifestyle behaviours for people on maintenance haemodialysis (KIDNEYTEXT): Study protocol for a randomised controlled trial

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    Introduction Managing nutrition is critical for reducing morbidity and mortality in patients on haemodialysis but adherence to the complex dietary restrictions remains problematic. Innovative interventions to enhance the delivery of nutritional care are needed. The aim of this phase II trial is to evaluate the feasibility and effectiveness of a targeted mobile phone text messaging system to improve dietary and lifestyle behaviours in patients on long-term haemodialysis. Methods and analysis Single-blinded randomised controlled trial with 6 months of follow-up in 130 patients on haemodialysis who will be randomised to either standard care or KIDNEYTEXT. The KIDNEYTEXT intervention group will receive three text messages per week for 6 months. The text messages provide customised dietary information and advice based on renal dietary guidelines and general healthy eating dietary guidelines, and motivation and support to improve behaviours. The primary outcome is feasibility including recruitment rate, drop-out rate, adherence to renal dietary recommendations, participant satisfaction and a process evaluation using semistructured interviews with a subset of purposively sampled participants. Secondary and exploratory outcomes include a range of clinical and behavioural outcomes and a healthcare utilisation cost analysis will be undertaken. Ethics and dissemination The study has been approved by the Western Sydney Local Health District Human Research Ethics Committee-Westmead. Results will be presented at scientific meetings and published in peer-reviewed publications. Trial registration number ACTRN12617001084370; Pre-results

    Application of a Resource Theory for Magic States to Fault-Tolerant Quantum Computing

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    Motivated by their necessity for most fault-tolerant quantum computation schemes, we formulate a resource theory for magic states. First, we show that robustness of magic is a well-behaved magic monotone that operationally quantifies the classical simulation overhead for a Gottesman-Knill-type scheme using ancillary magic states. Our framework subsequently finds immediate application in the task of synthesizing non-Clifford gates using magic states. When magic states are interspersed with Clifford gates, Pauli measurements, and stabilizer ancillas—the most general synthesis scenario—then the class of synthesizable unitaries is hard to characterize. Our techniques can place nontrivial lower bounds on the number of magic states required for implementing a given target unitary. Guided by these results, we have found new and optimal examples of such synthesis

    Identical particle scattering from a weakly coupled Bose-Einstein condensed gas

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    We calculate the scattering states and cross sections for a Bose-Einstein condensed dilute gas trapped in a spherical square well of finite depth. The interactions are treated in the scattering length approximation. We solve the Gross-Pitaevskii equation and the Bogoliubov equations for bound and scattering states. The results show that there are transparency effects reminiscent of those conjectured to occur for strongly coupled systems. When incident particle wavelengths λ are comparable to the well size a, exchange induced transparency enhancement is dramatic only for particular combinations of well depth, interaction strength, and particle number. For particles with large momenta (a/λ≫1),however, exchange with the condensate results in enhanced transmission for all coupling strengths. We calculated the rate of decay of the scattering states to leading order in anharmonic corrections to the Bogoliubov approximation and found the corresponding inelastic cross sections to be extremely small

    Re-integerization of fractional charges in the correlated quarter-filled band

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    Previous work has demonstrated the existence of soliton defect states with charges +/- e/2 in the limits of zero and of infinite on-site Coulomb interactions in the one-dimensional (1D) quarter-filled band. For large but finite on-site Coulomb interaction, the low temperature 2k_F bond distortion that occurs within the 4k_F bond-distorted phase is accompanied by charge-ordering on the sites. We show that a ``re-integerization'' of the defect charge occurs in this bond-charge density wave (BCDW) state due to a ``binding'' of the fractional charges. We indicate briefly possible implications of this result for mechanisms of organic superconductivity.Comment: 4 eps figure

    The "Daily Grind": Work, Commuting, and Their Impact on Political Participation

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    Past research demonstrates that free time is an important resource for political participation. We investigate whether two central drains on citizens? daily time?working and commuting?impact their level of political participation. The prevailing ?resources? model offers a quantity-focused view where additional time spent working or commuting reduces free time and should each separately decrease participation. We contrast this view to a ?commuter?s strain? hypothesis, which emphasizes time spent in transit as a psychologically onerous burden over and above the workday. Using national survey data, we find that time spent working has no effect on participation, while commuting significantly decreases participation. We incorporate this finding into a comprehensive model of the ?daily grind,? which factors in both socioeconomic status and political interest. Our analysis demonstrates that commuting leads to the greatest loss in political interest for low-income Americans, and that this loss serves as a main mechanism through which commuting erodes political participation

    Flux-tubes in three-dimensional lattice gauge theories

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    Flux-tubes in different representations of SU(2) and U(1) lattice gauge theories in three dimensions are measured. Wilson loops generate heavy ``quark-antiquark'' pairs in fundamental (j=1/2j=1/2), adjoint (j=1j=1), and quartet (j=3/2j=3/2) representations of SU(2). The first direct lattice measurements of the flux-tube cross-section Aj{\cal A}_j as a function of representation are made. It is found that Ajconstant{\cal A}_j \approx {\rm constant}, to about 10\%. Results are consistent with a connection between the string tension σj\sigma_j and Aj{\cal A}_j suggested by a simplified flux-tube model, σj=g2j(j+1)/(2Aj)\sigma_j = g^2 j(j+1) / (2 {\cal A}_j) [gg is the gauge coupling], given that σj\sigma_j scales like the Casimir j(j+1)j(j+1), as observed in previous lattice studies in both three and four dimensions. The results can discriminate among phenomenological models of the physics underlying confinement. Flux-tubes for singly- and doubly-charged Wilson loops in compact QED3_3 are also measured. It is found that the string tension scales as the squared-charge and the flux-tube cross-section is independent of charge to good approximation. These SU(2) and U(1) simulations lend some support, albeit indirectly, to a conjecture that the dual superconductor mechanism underlies confinement in compact gauge theories in both three and four dimensions.Comment: 15 pages (REVTEX 2.1). Figures: 11, not included (available by request from [email protected] by regular mail, postscript files, or one self-unpacking uuencoded file
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