Quantum discord and related measures of quantum correlations in XY chains

We examine the quantum correlations of spin pairs in the ground state of finite XY chains in a transverse field, by evaluating the quantum discord as well as other related entropic measures of quantum correlations. A brief review of the latter, based on generalized entropic forms, is also included. It is shown that parity effects are of crucial importance for describing the behavior of these measures below the critical field. It is also shown that these measures reach full range in the immediate vicinity of the factorizing field, where they become independent of separation and coupling range. Analytical and numerical results for the quantum discord, the geometric discord and other measures in spin chains with nearest neighbor coupling and in fully connected spin arrays are also provided.Comment: accepted in Int. J. Mod. Phys. B, special issue "Classical Vs Quantum correlations in composite systems" edited by L. Amico, S. Bose, V. Korepin and V. Vedra

Entanglement generation resonances in XY chains

We examine the maximum entanglement reached by an initially fully aligned state evolving in an XY Heisenberg spin chain placed in a uniform transverse magnetic field. Both the global entanglement between one qubit and the rest of the chain and the pairwise entanglement between adjacent qubits is analyzed. It is shown that in both cases the maximum is not a monotonous decreasing function of the aligning field, exhibiting instead a resonant behavior for low anisotropies, with pronounced peaks (a total of [n/2] peaks in the global entanglement for an $n$-spin chain), whose width is proportional to the anisotropy and whose height remains finite in the limit of small anisotropy. It is also seen that the maximum pairwise entanglement is not a smooth function of the field even in small finite chains, where it may exhibit narrow peaks above strict plateaus. Explicit analytical results for small chains, as well as general exact results for finite n-spin chains obtained through the Jordan-Wigner mapping, are discussed

Quantum correlations and least disturbing local measurements

We examine the evaluation of the minimum information loss due to an unread local measurement in mixed states of bipartite systems, for a general entropic form. Such quantity provides a measure of quantum correlations, reducing for pure states to the generalized entanglement entropy, while in the case of mixed states it vanishes just for classically correlated states with respect to the measured system, as the quantum discord. General stationary conditions are provided, together with their explicit form for general two-qubit states. Closed expressions for the minimum information loss as measured by quadratic and cubic entropies are also derived for general states of two-qubit systems. As application, we analyze the case of states with maximally mixed marginals, where a general evaluation is provided, as well as X states and the mixture of two aligned states.Comment: 10 pages, 3 figure

Preliminary experimental investigation into the use of recycled fibres from textile waste for the improvement of embankments

Failures that occurred in the last few decades highlighted the need to raise awareness about the emergent risk related to the impact localised degradation phenomena have on embankments. Common interventions aimed to improve embankments, such as the reconstruction of the damaged area or the injection of low-pressure grouts to fill fractures and burrows, may cause the weakening of the structure due to discontinuities between natural and treated zones. Moreover, since such repair techniques require huge volumes of materials, more sustainable solutions are encouraged. At the same time, the textile and fashion industries are looking for sustainable waste management and disposal strategies to face environmental problems concerned with the voluminous textile waste dispatched to landfills or incinerators. The use of soil mixed with textile waste in embankment improvement has been investigated to identify an effective engineering practice and to provide a strategy for the circular economy of textiles. Preliminary laboratory tests have been conducted on soil specimens collected from the Secchia River embankment, Northern Italy, to define the appropriate mixture proportions and to compare physical properties and hydro-mechanical behaviour of natural and treated soils. The results show that an appropriate fibre content offers manageable and relatively homogeneous mixtures. The indluence on soil consistency is mainly due to the textile fibre hydrophilic nature. The addition of fibres reduces the maximum dry density and increases the optimum water content. At low stress levels, the compressibility and hydraulic conductivity appear higher, however macro voids produced during sample preparation may alter the findings

Conditional purity and quantum correlation measures in two qubit mixed states

We analyze and show experimental results of the conditional purity, the quantum discord and other related measures of quantum correlation in mixed two-qubit states constructed from a pair of photons in identical polarization states. The considered states are relevant for the description of spin pair states in interacting spin chains in a transverse magnetic field. We derive clean analytical expressions for the conditional local purity and other correlation measures obtained as a result of a remote local projective measurement, which are fully verified by the experimental results. A simple exact expression for the quantum discord of these states in terms of the maximum conditional purity is also derived.Comment: 16 pages, 5 figures, minor changes, to be published in J. Phys.

Generalized entropic measures of quantum correlations

We propose a general measure of non-classical correlations for bipartite systems based on generalized entropic functions and majorization properties. Defined as the minimum information loss due to a local measurement, in the case of pure states it reduces to the generalized entanglement entropy, i.e., the generalized entropy of the reduced state. However, in the case of mixed states it can be non-zero in separable states, vanishing just for states diagonal in a general product basis, like the Quantum Discord. Simple quadratic measures of quantum correlations arise as a particular case of the present formalism. The minimum information loss due to a joint local measurement is also discussed. The evaluation of these measures in a few simple relevant cases is as well provided, together with comparison with the corresponding entanglement monotones.Comment: 9 pages, 2 figure

E-commerce and e-procurement: an outsourcing perspective

The make or buy dilemma has been largely analyzed in the field of Information Systems. The main reason for this type of literature thriving so much is that the Information Systems function was one of the first enterprise areas to be externalized. If traditionally only few activities, distant from the core business of the enterprises, have been externalized with the sole objective of gaining efficiency, in the late Nineties externalization of real company functions has started to be considered again, in some instances concerning activities that have always been considered core business. The role played by the management of organizational interdependencies was stressed and the fact that outsourcing was perceived according to solutions of organizational engineering was highlighted, steering enterprises towards new organizational design criteria. In fact, make or buy decisions require more and more that organizational variables be structured by processes and not by functions, precisely to ease the management of organizational interdependencies and make externalization decisions more transparent and objectively measurable. The research question of this paper aims at understanding how much can a particular form of electronic commerce, such as e-procurement, be categorized as a special form of outsourcing, intending this phenomenon as a hybrid organizational form, halfway between hierarchy and market. In order to categorize the outsourcing phenomenon from a theoretical standpoint, the Transaction Cost Theory (TCT) has been used, while the research method consists of a case study. In this paper the attention will be focused on a particular process only, i.e., procurement, in relation to the activities involved in the externalization process. The paper will analyze an outsourcing case applied to the entire macro-process of procurement. The conclusions will highlight the evolving trends in this research field, which appears to be affected by substantial changes and to be increasingly more volatile and influenced by multiple factors that are not always easily recognizable and measurable. The purpose of this paper in fact is to give a contribution to the formalization of an application subject, namely, externalization of procurement, largely diffused in practice although scarcely developed from a theoretical standpoint

Compressibilità e resistenza di un terreno arginale rinforzato con fibre da scarti tessili

L'articolo propone un'indagine sperimentale sul miglioramento e il rinforzo di terreni arginali tramite l'utilizzo di fibre da scarti tessili. Attraverso prove di laboratorio su terreni a cui sono state aggiunte fibre di lino e viscosa, sono stati valutati gli effetti della presenza delle fibre sulla compattazione e sulla resistenza del terreno. I risultati mostrano che l’aggiunta di fibre modifica la risposta del terreno in termini di compattazione riducendo la massima densità secca e aumentando il contenuto d’acqua ottimo. Inoltre, la presenza delle fibre può aumentare significativamente la resistenza al taglio del terreno, in funzione della loro geometria (i.e. diametro e lunghezza) e della quantità considerata. Ulteriori analisi su campioni di dimensioni maggiori sono raccomandate per studiare il comportamento dei terreni rinforzati con fibre tessili, a diverse scale

Shell Model Monte Carlo Investigation of Rare Earth Nuclei

We utilize the Shell Model Monte Carlo (SMMC) method to study the structure of rare earth nuclei. This work demonstrates the first systematic ``full oscillator shell plus intruder'' calculations in such heavy nuclei. Exact solutions of a pairing plus quadrupole hamiltonian are compared with mean field and SPA approximations in several Dysprosium isotopes from A=152-162, including the odd mass A=153. Basic properties of these nuclei at various temperatures and spin are explored. These include energy, deformation, moments of inertia, pairing channel strengths, band crossing, and evolution of shell model occupation numbers. Exact level densities are also calculated and, in the case of 162 Dy, compared with experimental data.Comment: 40 pages; 24 figures; 2 tables. Update includes correction of figure labe

In-farm cost of an outbreak of diarrhoea in lambs

This article analyses the cost of diarrhoea in lambs on dairy sheep farms located in Grosseto (Italy). Farmers’ profits have recently declined due to a stable product price but increasing production costs. Animal diseases have a cascade of effects on farm productivity. Lamb enteric disease outbreaks, which result in mortality in the herd and reduced weight gain, can drastically compromise the income of farmers. An economic analysis of the impact of an outbreak of diarrhoea in lambs was thus performed, evaluating the cost of disease based on the main visible production losses (such as mortality, reduced weight gain and variation in milk production). A sensitivity analysis was also conducted by applying different observed ranges of prevalence and mortality associated with the disease. Finally, an economic scenario analysis was performed, considering different in-farm management options for delivering lambs to the abattoir, i.e. early, standard and late delivery. The results showed that a dairy sheep farm with around 300 lambs that delivers them to the abattoir at 30 days of age would experience a loss of between 50 and 1200 Euro during an outbreak of diarrhoea with a prevalence of 34.21 (23.54–44.88)% and a mortality of 15.69 (9.98–21.4)%