Factorization and Criticality in the Anisotropic XY Chain via Correlations

In this review, we discuss the zero and finite temperature behavior of various bipartite quantum and total correlation measures, the skew information-based quantum coherence, and the local quantum uncertainty in the thermal ground state of the one-dimensional anisotropic XY model in transverse magnetic field. We compare the ability of considered measures to correctly detect or estimate the quantum critical point and the non-trivial factorization point possessed by the spin chain.Comment: 29 pages, 8 figures. A review paper accepted for publication in the special issue Entanglement Entropy in the journal Entrop

SCINTILLA A European project for the development of scintillation detectors and new technologies for nuclear security

Europe monitors transits using radiation detectors to prevent illicit trafficking of nuclear materials. The SCINTILLA project aims to develop a toolbox of innovative technologies designed to address different usage cases. This article will review the scope, approach, results of the first benchmark campaign and future plans of the SCINTILLA project.Comment: To appear on the Proceedings of the 13th ICATPP Conference on Astroparticle, Particle, Space Physics and Detectors for Physics Applications, Villa Olmo (Como, Italy), 23--27 October, 2013, to be published by World Scientific (Singapore

Non-Markovian Dynamics of Quantum Discord

We evaluate the quantum discord dynamics of two qubits in independent and common non-Markovian environments. We compare the dynamics of entanglement with that of quantum discord. For independent reservoirs the quantum discord vanishes only at discrete instants whereas the entanglement can disappear during a finite time interval. For a common reservoir, quantum discord and entanglement can behave very differently with sudden birth of the former but not of the latter. Furthermore, in this case the quantum discord dynamics presents sudden changes in the derivative of its time evolution which is evidenced by the presence of kinks in its behavior at discrete instants of time.Comment: 6 pages, 4 figure

Quantum Correlations and Coherence in Spin-1 Heisenberg Chains

We explore quantum and classical correlations along with coherence in the ground states of spin-1 Heisenberg chains, namely the one-dimensional XXZ model and the one-dimensional bilinear biquadratic model, with the techniques of density matrix renormalization group theory. Exploiting the tools of quantum information theory, that is, by studying quantum discord, quantum mutual information and three recently introduced coherence measures in the reduced density matrix of two nearest neighbor spins in the bulk, we investigate the quantum phase transitions and special symmetry points in these models. We point out the relative strengths and weaknesses of correlation and coherence measures as figures of merit to witness the quantum phase transitions and symmetry points in the considered spin-1 Heisenberg chains. In particular, we demonstrate that as none of the studied measures can detect the infinite order Kosterlitz-Thouless transition in the XXZ model, they appear to be able to signal the existence of the same type of transition in the biliear biquadratic model. However, we argue that what is actually detected by the measures here is the SU(3) symmetry point of the model rather than the infinite order quantum phase transition. Moreover, we show in the XXZ model that examining even single site coherence can be sufficient to spotlight the second-order phase transition and the SU(2) symmetry point.Comment: 8 pages. 5 figure

Quantum coherence and uncertainty in the anisotropic XY chain

We explore the local quantum coherence and the local quantum uncertainty, based on Wigner-Yanase skew information, in the ground state of the anisotropic spin-1/2 XY chain in transverse magnetic field. We show that the skew information, as a figure of merit, supplies the necessary information to reveal the occurrence of the second order phase transition and the completely factorized ground state in the XY model. Additionally, in the same context, we also discuss the usefulness of a simple experimentally friendly lower bound of local quantum coherence. Furthermore, we demonstrate how the connection between the appearance of non-analyticities in the local quantum uncertainty of the ground state and the quantum phase transitions does not hold in general, by providing explicit examples of the situation. Lastly, we discuss the ability of the local quantum coherence to accurately estimate the critical point of the phase transition, and investigate the robustness of the factorization phenomenon at low temperatures.Comment: 7 pages, 6 figures. Title changed. Close to published versio

The high-voltage system for the LHCb RICH hybrid photon detectors

We describe the characterization of the high-voltage (HV) distribution system designed and produced for the pixel hybrid photon detectors of the ring imaging Cherenkov counters of the LHCb experiment. The HV system consists of a series of printed circuit boards with a specific layout designed to prevent any discharge arising from high electric fields. The system has dedicated monitoring and control features to supervise HV set-up during data taking. The full production of the HV system has been now completed and all the boards have been fully characterized and installed in the detector, which is currently being commissioned. © 2008 Elsevier B.V. All rights reserved

On-Sight and Red-Point Climbing : Changes in Performance and Route-Finding Ability in Male Advanced Climbers

Aim: In lead climbing, the ascent of the route can be defined as on-sight or red-point. On-sight is the more challenging style since it demands greater physiological and psychological commitment. The differences between the two modes in advanced climbers have not been studied much. Two essential skills needed to optimize performance, in both on-sight and in red-point climbing, are route interpretation (RI) ability and movements sequence recall. Therefore, this study aimed to compare performance between on-sight and red-point ascent in advanced climbers and evaluate how a climber\u2019s RI ability and movement sequences recall might change before and after on-sight and red-point climbing. Methods: Eighteen advanced male climbers (age 29.2 \ub1 4.7 years, body mass 67.8 \ub1 3.6 kg, stature 175.2 \ub1 2.4 cm, best red-point and on-sight grades 7b+/8a and 7a+/7b+, respectively) were video-recorded during the route ascent in on-sight and red-point modes to evaluate performance and to measure static and dynamic action times. RI ability and movement sequence recall were assessed before and after each climb. Level of anxiety was evaluated via a self-report questionnaire. Heart rate (fH), lactate concentration, ([La\u2013]), and rating of perceived exertion (RPE) were detected during and after each climb. Results: Compared to on-sight, an improvement in performance was observed in a red-point climb: the ascent was faster (148.7 \ub1 13.6 s and 179.5 \ub1 12.5 s, respectively, P < 0.05), smoother (significant reduction in exploratory moves and in stops times, P < 0.05), less demanding physiologically (lower fHpeak and [La\u2013]peak, P < 0.05), and psychologically (lower RPE, cognitive and somatic anxiety and higher self-confidence, P < 0.05). The RI ability was improved in red-point versus on-sight and, in the same mode, between pre and post ascent. Conclusion: Red-point climbing was found to be less demanding than on-sight, both physiologically and psychologically, under the conditions investigated by this study. Our findings suggest that RI is a trainable skill and underscore the importance of including specific techniques in training programs designed to improve interaction between perceptual, psychological, and physiological factors