24 research outputs found
Current transport properties and phase diagram of a Kitaev chain with long-range pairing
We describe a method to probe the quantum phase transition between the
short-range topological phase and the long-range topological phase in the
superconducting Kitaev chain with long-range pairing, both exhibiting subgap
modes localized at the edges. The method relies on the effects of the finite
mass of the subgap edge modes in the long-range regime (which survives in the
thermodynamic limit) on the single-particle scattering coefficients through the
chain connected to two normal leads. Specifically, we show that, when the leads
are biased at a voltage V with respect to the superconducting chain, the Fano
factor is either zero (in the short-range correlated phase) or 2e (in the
long-range correlated phase). As a result, we find that the Fano factor works
as a directly measurable quantity to probe the quantum phase transition between
the two phases. In addition, we note a remarkable "critical fractionalization
effect" in the Fano factor, which is exactly equal to e along the quantum
critical line. Finally, we note that a dual implementation of our proposed
device makes it suitable as a generator of large-distance entangled
two-particle states.Comment: 24 pages, 8 .eps figures Published versio
Tunable spin/charge Kondo effect at a double superconducting island connected to two spinless quantum wires
We propose that a pertinently engineered double superconducting island
connected to two spinless one-dimensional conducting leads can work as a
tunable (iso)spin Kondo and charge Kondo system, with the lead index regarded
as an effective isospin degree of freedom. We evidence how, by tuning a single
gate voltage applied to the island, it is possible to make the system switch
from the (iso)spin Kondo to the charge-Kondo phase, passing across an
intermediate phase, in which the Kondo impurity is effectively irrelevant for
the low-temperature behavior of the system.
Eventually, we evidence how to probe the various phases by measuring the ac
conductance tensor of our system, by emphasizing the features that should allow
to identify the onset of the so far quite elusive "charge-2" charge-Kondo
effect.Comment: 29 pages, 6 .eps figures, published versio
Objective assessment of image quality in conventional and digital mammography taking into account dynamic range
The goal of this work is to develop a method to objectively compare the performance of a digital and a screen-film mammography system in terms of image quality. The method takes into account the dynamic range of the image detector, the detection of high and low contrast structures, the visualisation of the images and the observer response. A test object, designed to represent a compressed breast, was constructed from various tissue equivalent materials ranging from purely adipose to purely glandular composition. Different areas within the test object permitted the evaluation of low and high contrast detection, spatial resolution and image noise. All the images (digital and conventional) were captured using a CCD camera to include the visualisation process in the image quality assessment. A mathematical model observer (non-prewhitening matched filter), that calculates the detectability of high and low contrast structures using spatial resolution, noise and contrast, was used to compare the two technologies. Our results show that for a given patient dose, the detection of high and low contrast structures is significantly better for the digital system than for the conventional screen-film system studied. The method of using a test object with a large tissue composition range combined with a camera to compare conventional and digital imaging modalities can be applied to other radiological imaging techniques. In particular it could be used to optimise the process of radiographic reading of soft copy image
Dissipation driven dynamical topological phase transitions in two-dimensional superconductors
By quenching the interaction strength, we induce and study a topological
dynamical phase transition between superconducting phases of a planar fermionic
model. Using the Lindblad Master Equation approach to account for the
interactions of Bogoliubov quasiparticles among themselves and with the
fluctuations of the superconducting order parameter, we derive the
corresponding relaxation dynamics of the order parameter. To fully characterize
the phase transition, we also compute the fidelity and the spin-Hall
conductance of the system. Our approach provides us crucial informations for
experimental implementations, such as the dependence of the critical time on
the system-bath coupling.Comment: 9 pages, 6 .eps figures. Includes Supplemental Material as a part of
the Main Fil
Lindblad master equation approach to the dissipative quench dynamics of planar superconductors
We employ the Lindblad Master Equation method to study the nonequilibrium
dynamics following a parametric quench in the Hamiltonian of an open,
two-dimensional superconducting system coupled to an external bath. Within our
approach we show how, in the open system, the dissipation works as an effective
stabilization mechanism in the time evolution of the system after the quench.
Eventually, we evidence how the mismatch between the phases corresponding to
the initial and to the final state of the system determines a dynamical phase
transition between the two distinct phases. Our method allows for fully
characterizing the dynamical phase transition in an open system in several
cases of physical relevance, by means of a combined study of the time dependent
superconducting gap and of the fidelity between density matrices.Comment: 14 pages, 7 .eps figure
Severe hypertension and massive proteinuria in a newborn with renal artery stenosis
Renal vein thrombosis and the congenital nephrotic syndrome have been associated with nephrotic-range proteinuria/nephrotic syndrome and hypertension in the newborn period. We describe a newborn with severe hypertension and proteinuria secondary to unilateral renal artery stenosis. Proteinuria completely disappeared with blood pressure control (with sodium nitroprusside and an angiotensin-converting enzyme inhibitor). Although renin was not measured, we speculate that proteinuria might have been induced by a high renin state, and was controlled by the angiotensin-converting enzyme inhibito
Improving Breast Cancer Education: The Case of an Evolving Multidisciplinary Module for Undergraduate Medical Students (Lausanne Medical School, 1993-2008)
Breast cancer is a public health issue in numerous countries. Multidisciplinary collaboration is required for patient care, research, and also education of future physicians. This paper uses Kern's framework for curriculum design to demonstrate how a breast diseases module for undergraduate medical students created in 1993 evolved over 15years. The main outcomes of program refinements were better integrated course content, the development of electronic course documents, and implementation of computer-aided small group learning. A main future challenge is to further develop efficient instructional strategies in line with well-defined learning needs for undergraduate student
Can multipartite entanglement be characterized by two-point connected correlation functions?
We discuss under which conditions multipartite entanglement in mixed quantum states can be characterized only in terms of two-point connected correlation functions, as it is the case for pure states. In turn, the latter correlations are defined via a suitable combination of (disconnected) one- and two-point correlation functions. In contrast to the case of pure states, conditions to be satisfied turn out to be rather severe. However, we were able to identify some interesting cases, as when the point-independence is valid of the one-point correlations in each possible decomposition of the density matrix, or when the operators that enter in the correlations are (semi-)positive/negative defined
Improving breast cancer education: the case of an evolving multidisciplinary module for undergraduate medical students (lausanne medical school, 1993-2008).
Breast cancer is a public health issue in numerous countries. Multidisciplinary collaboration is required for patient care, research, and also education of future physicians. This paper uses Kern's framework for curriculum design to demonstrate how a breast diseases module for undergraduate medical students created in 1993 evolved over 15 years. The main outcomes of program refinements were better integrated course content, the development of electronic course documents, and implementation of computer-aided small group learning. A main future challenge is to further develop efficient instructional strategies in line with well-defined learning needs for undergraduate students