Revealing quantum statistics with a pair of distant atoms

Quantum statistics have a profound impact on the properties of systems composed of identical particles. In this Letter, we demonstrate that the quantum statistics of a pair of identical massive particles can be probed by a direct measurement of the exchange symmetry of their wave function even in conditions where the particles always remain spatially well separated and thus the exchange contribution to their interaction energy is negligible. We present two protocols revealing the bosonic or fermionic nature of a pair of particles and discuss possible implementations with a pair of trapped atoms or ions.Comment: 4+13 pages, v2 corresponds to the version published by PR

Damage as Gamma-limit of microfractures in anti-plane linearized elasticity

A homogenization result is given for a material having brittle inclusions arranged in a periodic structure. <br/> According to the relation between the softness parameter and the size of the microstructure, three different limit models are deduced via Gamma-convergence. <br/> In particular, damage is obtained as limit of periodically distributed microfractures

Propagation and spectral properties of quantum walks in electric fields

We study one-dimensional quantum walks in a homogeneous electric field. The field is given by a phase which depends linearly on position and is applied after each step. The long time propagation properties of this system, such as revivals, ballistic expansion and Anderson localization, depend very sensitively on the value of the electric field $\Phi$, e.g., on whether $\Phi/(2\pi)$ is rational or irrational. We relate these properties to the continued fraction expansion of the field. When the field is given only with finite accuracy, the beginning of the expansion allows analogous conclusions about the behavior on finite time scales.Comment: 7 pages, 4 figure

Electric quantum walks with individual atoms

We report on the experimental realization of electric quantum walks, which mimic the effect of an electric field on a charged particle in a lattice. Starting from a textbook implementation of discrete-time quantum walks, we introduce an extra operation in each step to implement the effect of the field. The recorded dynamics of such a quantum particle exhibits features closely related to Bloch oscillations and interband tunneling. In particular, we explore the regime of strong fields, demonstrating contrasting quantum behaviors: quantum resonances vs. dynamical localization depending on whether the accumulated Bloch phase is a rational or irrational fraction of 2\pi.Comment: 5 pages, 4 figure

Coherent transport of atomic wave packets in amplitude-modulated vertical optical lattices

We report on the realization of dynamical control of transport for ultra-cold Sr88 atoms loaded in an accelerated and amplitude-modulated 1D optical lattice. We tailor the energy dispersion of traveling wave packets and reversibly switch between Wannier-Stark localization and driven transport based on coherent tunneling. Within a Loschmidt-echo scheme where the atomic group velocities are reversed at once, we demonstrate a novel mirror for matter waves working independently of the momentum state and discuss possible applications to force measurements at micrometric scales

A simple abstraction of arrays and maps by program translation

We present an approach for the static analysis of programs handling arrays, with a Galois connection between the semantics of the array program and semantics of purely scalar operations. The simplest way to implement it is by automatic, syntactic transformation of the array program into a scalar program followed analysis of the scalar program with any static analysis technique (abstract interpretation, acceleration, predicate abstraction,.. .). The scalars invariants thus obtained are translated back onto the original program as universally quantified array invariants. We illustrate our approach on a variety of examples, leading to the " Dutch flag " algorithm

Arbitrary-order Hilbert spectral analysis and intermittency in solar wind density fluctuations

The properties of inertial and kinetic range solar wind turbulence have been investigated with the arbitrary-order Hilbert spectral analysis method, applied to high-resolution density measurements. Due to the small sample size, and to the presence of strong non-stationary behavior and large-scale structures, the classical structure function analysis fails to detect power law behavior in the inertial range, and may underestimate the scaling exponents. However, the Hilbert spectral method provides an optimal estimation of the scaling exponents, which have been found to be close to those for velocity fluctuations in fully developed hydrodynamic turbulence. At smaller scales, below the proton gyroscale, the system loses its intermittent multiscaling properties, and converges to a monofractal process. The resulting scaling exponents, obtained at small scales, are in good agreement with those of classical fractional Brownian motion, indicating a long-term memory in the process, and the absence of correlations around the spectral break scale. These results provide important constraints on models of kinetic range turbulence in the solar wind

Catalysis in non--local quantum operations

We show how entanglement can be used, without being consumed, to accomplish unitary operations that could not be performed with out it. When applied to infinitesimal transformations our method makes equivalent, in the sense of Hamiltonian simulation, a whole class of otherwise inequivalent two-qubit interactions. The new catalysis effect also implies the asymptotic equivalence of all such interactions.Comment: 4 pages, revte

Recent Progress in Shearlet Theory: Systematic Construction of Shearlet Dilation Groups, Characterization of Wavefront Sets, and New Embeddings

The class of generalized shearlet dilation groups has recently been developed to allow the unified treatment of various shearlet groups and associated shearlet transforms that had previously been studied on a case-by-case basis. We consider several aspects of these groups: First, their systematic construction from associative algebras, secondly, their suitability for the characterization of wavefront sets, and finally, the question of constructing embeddings into the symplectic group in a way that intertwines the quasi-regular representation with the metaplectic one. For all questions, it is possible to treat the full class of generalized shearlet groups in a comprehensive and unified way, thus generalizing known results to an infinity of new cases. Our presentation emphasizes the interplay between the algebraic structure underlying the construction of the shearlet dilation groups, the geometric properties of the dual action, and the analytic properties of the associated shearlet transforms.Comment: 28 page

Antinuclear antibodies (ANA) in chronic hepatitis C virus infection: correlates of positivity and clinical relevance.

We examined correlates of antinuclear antibody (ANA) positivity (ANA+) in individuals with chronic hepatitis C virus (HCV) infection and the effect of positivity on clinical outcome of HCV. Pretreatment sera from 645 patients from three centres in Sweden (n = 225), the UK (n = 207) and Italy (n = 213) were evaluated by indirect immunofluorescence on Hep-2 cells for ANA pattern and titre by a single laboratory. Liver biopsies were all scored by one pathologist. A total of 258 patients were subsequently treated with interferon monotherapy. There was a significant difference in the prevalence of ANA (1:40) by geographic location: Lund 4.4%, London 8.7%, Padova 10.3% [odds ratio (OR) = 0.66; 95% CI: 0.46-0.94; P = 0.023]. Duration of HCV infection, age at infection, current age, route of infection, viral genotype, alcohol consumption, fibrosis stage and inflammatory score were not correlated with ANA+ or ANA pattern. Female gender was correlated with ANA+ and this association persisted in multivariable analyses (OR = 3.0; P = 0.002). Increased plasma cells were observed in the liver biopsies of ANA-positive individuals compared with ANA-negative individuals, while a trend towards decreased lymphoid aggregates was observed [hazard ratio (HR) = 9.0, P = 0.037; HR = 0.291, P = 0.118, respectively]. No correlations were observed between ANA positivity and nonresponse to therapy (OR = 1.4; P = 0.513), although ANA+ was correlated with faster rates of liver fibrosis, this was not statistically significant (OR = 1.8; P = 0.1452). Low titre ANA+ should not be a contraindication for interferon treatment. Our observation of increased plasma cells in ANA+ biopsies might suggest B-cell polyclonal activity with a secondary clinical manifestation of increased serum immunoglobulins