558 research outputs found
Spin-Orbit Coupling in LaAlO/SrTiO interfaces: Magnetism and Orbital Ordering
The combination of Rashba spin-orbit coupling and electron correlations can
induce unusual phenomena in the metallic interface between SrTiO and
LaAlO. We consider effects of Rashba spin-orbit coupling at this interface
in the context of the recent observation of anisotropic magnetism. Firstly, we
show how Rashba spin-orbit coupling in a system near a band-edge can account
for the observed magnetic anisotropy. Secondly, we investigate the coupling
between in-plane magnetic-moment anisotropy and nematicity in the form of an
orbital imbalance between d / d orbitals. We estimate this
coupling to be substantial in the low electron density regime. Such an orbital
ordering can affect magneto transport
On Approximation of the Eigenvalues of Perturbed Periodic Schrodinger Operators
This paper addresses the problem of computing the eigenvalues lying in the
gaps of the essential spectrum of a periodic Schrodinger operator perturbed by
a fast decreasing potential. We use a recently developed technique, the so
called quadratic projection method, in order to achieve convergence free from
spectral pollution. We describe the theoretical foundations of the method in
detail, and illustrate its effectiveness by several examples.Comment: 17 pages, 2 tables and 2 figure
No-Switching Quantum Key Distribution using Broadband Modulated Coherent Light
We realize an end-to-end no-switching quantum key distribution protocol using
continuous-wave coherent light. We encode weak broadband Gaussian modulations
onto the amplitude and phase quadratures of light beams at the Shannon's
information limit. Our no-switching protocol achieves high secret key rate via
a post-selection protocol that utilizes both quadrature information
simultaneously. We establish a secret key rate of 25 Mbits/s for a lossless
channel and 1 kbit/s, per 17 MHz of detected bandwidth, for 90% channel loss.
Since our scheme is truly broadband, it can potentially deliver orders of
magnitude higher key rates by extending the encoding bandwidth with higher-end
telecommunication technology.Comment: 5 pages, 3 figures, publishe
On 1-qubit channels
The entropy H_T(rho) of a state rho with respect to a channel T and the
Holevo capacity of the channel require the solution of difficult variational
problems. For a class of 1-qubit channels, which contains all the extremal
ones, the problem can be significantly simplified by associating an Hermitian
antilinear operator theta to every channel of the considered class. The
concurrence of the channel can be expressed by theta and turns out to be a flat
roof. This allows to write down an explicit expression for H_T. Its maximum
would give the Holevo (1-shot) capacity.Comment: 12 pages, several printing or latex errors correcte
Surgery for Port-Wine Stains: A Systematic Review
Background: Port-wine stains (PWS) are congenital low-flow vascular malformations of the skin. PWS tend to become thicker and darker with time. Laser therapy is the gold standard and the first-line therapy for treating PWS. However, some resistant PWS, or PWS that have tissue hypertrophy, do not respond to this therapy. Our aim is to evaluate the role of surgery in the treatment of PWS birthmarks. Methods: A literature search was performed in PubMed, Scopus, Web of Science (WOS) and Google Scholar for all papers dealing with surgery for port-wine stains, from January 2010 to December 2020 using the search strings: (capillary vascular malformation OR port-wine stains OR Sturge Weber Syndrome OR sws OR pws) AND (surgical OR surgery). Results: Ten articles were identified and used for analysis. They were almost all case series with a short follow up period and lacked an objective–systematic score of evaluation. Conclusions: Delay in treatment of port wine stains may result in soft tissue and bone hypertrophy or nodules with disfiguring or destructive characteristics. The correction of PWS-related facial asymmetry often requires bone surgery followed by soft tissue corrections to achieve a more harmonious, predictable result
Local versus non-local information in quantum information theory: formalism and phenomena
In spite of many results in quantum information theory, the complex nature of
compound systems is far from being clear. In general the information is a
mixture of local, and non-local ("quantum") information. To make this point
more clear, we develop and investigate the quantum information processing
paradigm in which parties sharing a multipartite state distill local
information. The amount of information which is lost because the parties must
use a classical communication channel is the deficit. This scheme can be viewed
as complementary to the notion of distilling entanglement. After reviewing the
paradigm, we show that the upper bound for the deficit is given by the relative
entropy distance to so-called psuedo-classically correlated states; the lower
bound is the relative entropy of entanglement. This implies, in particular,
that any entangled state is informationally nonlocal i.e. has nonzero deficit.
We also apply the paradigm to defining the thermodynamical cost of erasing
entanglement. We show the cost is bounded from below by relative entropy of
entanglement. We demonstrate the existence of several other non-local
phenomena. For example,we prove the existence of a form of non-locality without
entanglement and with distinguishability. We analyze the deficit for several
classes of multipartite pure states and obtain that in contrast to the GHZ
state, the Aharonov state is extremely nonlocal (and in fact can be thought of
as quasi-nonlocalisable). We also show that there do not exist states, for
which the deficit is strictly equal to the whole informational content (bound
local information). We then discuss complementary features of information in
distributed quantum systems. Finally we discuss the physical and theoretical
meaning of the results and pose many open questions.Comment: 35 pages in two column, 4 figure
Topological superfluid 3He-B in magnetic field and Ising variable
The topological superfluid 3He-B provides many examples of the interplay of
symmetry and topology. Here we consider the effect of magnetic field on
topological properties of 3He-B. Magnetic field violates the time reversal
symmetry. As a result, the topological invariant supported by this symmetry
ceases to exist; and thus the gapless fermions on the surface of 3He-B are not
protected any more by topology: they become fully gapped. Nevertheless, if
perturbation of symmetry is small, the surface fermions remain relativistic
with mass proportional to symmetry violating perturbation -- magnetic field.
The 3He-B symmetry gives rise to the Ising variable I=+/- 1, which emerges in
magnetic field and which characterizes the states of the surface of 3He-B. This
variable also determines the sign of the mass term of surface fermions and the
topological invariant describing their effective Hamiltonian. The line on the
surface, which separates the surface domains with different I, contains 1+1
gapless fermions, which are protected by combined action of symmetry and
topology.Comment: 5 pages, JETP Letters style, no figures, version submitted to JETP
Letter
Magnetoelectric Effect and Spontaneous Polarization in HoFe(BO) and HoNdFe(BO)
The thermodynamic, magnetic, dielectric, and magnetoelectric properties of
HoFe(BO) and HoNdFe(BO) are
investigated. Both compounds show a second order Ne\'{e}l transition above 30 K
and a first order spin reorientation transition below 10 K.
HoFe(BO) develops a spontaneous electrical polarization below the
Ne\'{e}l temperature (T) which is diminished in external magnetic fields.
No magnetoelectric effect could be observed in HoFe(BO). In
contrast, the solid solution HoNdFe(BO) exhibits
both, a spontaneous polarization below T and a magnetoelectric effect at
higher fields that extends to high temperatures. The superposition of
spontaneous polarization, induced by the internal magnetic field in the ordered
state, and the magnetoelectric polarizations due to the external field results
in a complex behavior of the total polarization measured as a function of
temperature and field.Comment: 12 pages, 15 figure
Multiple General Anesthesia in Children: A Systematic Review of Its Effect on Neurodevelopment
The effect of multiple general anesthesia (mGA) procedures administered in early life is a critical theme and has led the Food and Drug Administration (FDA) to issue an alert. This systematic review seeks to explore the potential effects on neurodevelopment of mGA on patients under 4 years. The Medline, Embase and Web of Science databases were searched for publications up to 31 March 2021. The databases were searched for publications regarding “children multiple general anesthesia OR pediatric multiple general anesthesia”. Case reports, animal studies and expert opinions were excluded. Systematic reviews were not included, but they were screened to identify any possible additional information. A total of 3156 studies were identified. After removing the duplicates, screening the remaining records and analyzing the systematic reviews’ bibliography, 10 studies were considered suitable for inclusion. Comprehensively, a total cohort of 264.759 unexposed children and 11.027 exposed children were assessed for neurodevelopmental outcomes. Only one paper did not find any statistically significant difference between exposed and unexposed children in terms of neurodevelopmental alterations. Controlled studies on mGA administered before 4 years of age support that there might be a greater risk of neurodevelopmental delay in children receiving mGA, warranting the need for careful risk/benefit considerations
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