Proof of finite surface code threshold for matching

The field of quantum computation currently lacks a formal proof of experimental feasibility. Qubits are fragile and sophisticated quantum error correction is required to achieve reliable quantum computation. The surface code is a promising quantum error correction code, requiring only a physically reasonable 2-D lattice of qubits with nearest neighbor interactions. However, existing proofs that reliable quantum computation is possible using this code assume the ability to measure four-body operators and, despite making this difficult to realize assumption, require that the error rate of these operator measurements is less than 10^-9, an unphysically low target. High error rates have been proved tolerable only when assuming tunable interactions of strength and error rate independent of distance, which is also unphysical. In this work, given a 2-D lattice of qubits with only nearest neighbor two-qubit gates, and single-qubit measurement, initialization, and unitary gates, all of which have error rate p, we prove that arbitrarily reliable quantum computation is possible provided p<7.4x10^-4, a target that many experiments have already achieved. This closes a long-standing open problem, formally proving the experimental feasibility of quantum computation under physically reasonable assumptions.Comment: 5 pages, 4 figures, published versio

Simulations of aging and plastic deformation in polymer glasses

We study the effect of physical aging on the mechanical properties of a model polymer glass using molecular dynamics simulations. The creep compliance is determined simultaneously with the structural relaxation under a constant uniaxial load below yield at constant temperature. The model successfully captures universal features found experimentally in polymer glasses, including signatures of mechanical rejuvenation. We analyze microscopic relaxation timescales and show that they exhibit the same aging characteristics as the macroscopic creep compliance. In addition, our model indicates that the entire distribution of relaxation times scales identically with age. Despite large changes in mobility, we observe comparatively little structural change except for a weak logarithmic increase in the degree of short-range order that may be correlated to an observed decrease in aging with increasing load.Comment: 9 pages, 12 figure

THE TRACES OF THE PAST: INFORMATIVE TOOLS FOR THE RECONSTRUCTION OF AURELIAN WALLS IN RIONE TESTACCIO

Abstract. Rome has a great cultural heritage, formed by the stratification of styles and political influences from different eras. The different eras and architectural styles that have defined the city in the two millennia of history, make each part unique in its kind. This succession of changes has by necessity led to the denial of some archaeologies that in past ages were pivotal points in the development of the ancient city. The research presented here is intended to analyze and reconstruct the archeology of the river stretch of the Aurelian Walls on the Lungotevere Testaccio partly disappeared from the architectural landscape of the city. The research was set in two main phases, the first based on the two-dimensional study of the lost fabric, focusing on the cartographic study and the digitization of them in the GIS environment. The second one still under development foresees the digitalization of the threedimensional elements detected and the insertion of these within the dedicated platforms.</p

INFORMATION MODELING AND LANDSCAPE: INTERVENTION METHODOLOGY FOR READING COMPLEX SYSTEMS

Abstract. When we talk about landscape and in particular landscape architecture, we refer to a living structure in continuous evolution and in clear contrast to the aesthetic and geometric immobility of the single architectural building. By landscape we mean a complex set of transformations of a historical and biological nature; the times of these components are very different, but they work in a single cycle and in symbiosis between them. This set is inseparable from what happens in the present, we must always think about who lives the reality and know how to interpret the different subjective perceptions of a space. The theme of landscape representation is a subject of difficult development, not only for the multiplicity of elements involved in a single system, but for the dynamism and continuous transformation of the element that one wants to study. The intrinsic multidisciplinarity in this field imposes different visions on the methodology to be used to understand and in the end represent. We must ask ourselves which is the problem in understanding how nowadays it is possible to develop a system capable of grouping the different needs that arise from the study of the landscape and which tools must be used in surveying and representation. To date, in the Italian context, the landscape project and its graphic representation is steady to the production of static images, realized with two-dimensional or three-dimensional digital drawing software, representing only the frames of reality, within the territory survey, or of future developments regarding projects. This methodology of representation imposes strong limits in the understanding of which systems and elements come into play when one enters into relationship with a living architecture.</p

Non-Gaussian fluctuations in stochastic models with absorbing barriers

The dynamics of a one-dimensional stochastic model is studied in presence of an absorbing boundary. The distribution of fluctuations is analytically characterized within the generalized van Kampen expansion, accounting for higher order corrections beyond the conventional Gaussian approximation. The theory is shown to successfully capture the non Gaussian traits of the sought distribution returning an excellent agreement with the simulations, for {\it all times} and arbitrarily {\it close} to the absorbing barrier. At large times, a compact analytical solution for the distribution of fluctuations is also obtained, bridging the gap with previous investigations, within the van Kampen picture and without resorting to alternative strategies, as elsewhere hypothesized.Comment: 2 figures, submitted to Phys. Rev. Let

Topological code Autotune

Many quantum systems are being investigated in the hope of building a large-scale quantum computer. All of these systems suffer from decoherence, resulting in errors during the execution of quantum gates. Quantum error correction enables reliable quantum computation given unreliable hardware. Unoptimized topological quantum error correction (TQEC), while still effective, performs very suboptimally, especially at low error rates. Hand optimizing the classical processing associated with a TQEC scheme for a specific system to achieve better error tolerance can be extremely laborious. We describe a tool Autotune capable of performing this optimization automatically, and give two highly distinct examples of its use and extreme outperformance of unoptimized TQEC. Autotune is designed to facilitate the precise study of real hardware running TQEC with every quantum gate having a realistic, physics-based error model.Comment: 13 pages, 17 figures, version accepted for publicatio

A Simulation of One Dimensional Contaminant Transport

In this note we present some simulations and some analytical solutions, in closed form, of the advection dispersion equation in one-dimensional domain. These solutions are obtained for not-conservative solutes by considering time-dependent, third type (Robin) boundary condition for first order reaction and linear equilibrium absorption. The Robin boundary condition models a combined production-decay function. The model is useful to describe sources as the contaminant release due to the failure of an underground pipelines or radioactive decay series. The developed analytical model gives rise to analytical solutions not present in the literature. Further, we remark that, for particular values of the rate constants involved in the model, our results furnish values which are in agreement with results present in the literature

Visualization of Coherent Destruction of Tunneling in an Optical Double Well System

We report on a direct visualization of coherent destruction of tunneling (CDT) of light waves in a double well system which provides an optical analog of quantum CDT as originally proposed by Grossmann, Dittrich, Jung, and Hanggi [Phys. Rev. Lett. {\bf 67}, 516 (1991)]. The driven double well, realized by two periodically-curved waveguides in an Er:Yb-doped glass, is designed so that spatial light propagation exactly mimics the coherent space-time dynamics of matter waves in a driven double-well potential governed by the Schr\"{o}dinger equation. The fluorescence of Er ions is exploited to image the spatial evolution of light in the two wells, clearly demonstrating suppression of light tunneling for special ratios between frequency and amplitude of the driving field.Comment: final versio

A clinical pilot study on the effect of the probiotic Lacticaseibacillus rhamnosus TOM 22.8 strain in women with vaginal dysbiosis

Lactobacilli with probiotic features play an essential role in maintaining a balanced vaginal microbiota and their administration has been suggested for the treatment and prevention of vaginal dysbiosis. The present study was aimed to in vitro and in vivo investigate the probiotic potential of the Lacticaseibacillus rhamnosus TOM 22.8 strain, isolated from the vaginal ecosystem of a healthy woman. For this purpose, safety and functional properties were in depth evaluated. The strain exhibited a broad spectrum of antagonistic activity against vaginal pathogens; adhesion capacity to both the vaginal VK2/E6E7 and the intestinal Caco-2 cells; anti-inflammatory and antioxidant activities, suggesting its promising probiotic features. In addition, an in vivo pilot-study was planned. Based on both clinical and microbiological parameters, the oral or vaginal strain administration, determined a significant pathogens reduction after 10 days of administration and a maintenance of eubiosis up to 30 days after the end of the treatment. Therefore, the L. rhamnosus TOM 22.8 strain can be proposed as valuable oral and/or vaginal treatment for vaginal dysbiosis