15,007 research outputs found
Convex Trace Functions on Quantum Channels and the Additivity Conjecture
We study a natural generalization of the additivity problem in quantum
information theory: given a pair of quantum channels, then what is the set of
convex trace functions that attain their maximum on unentangled inputs, if they
are applied to the corresponding output state?
We prove several results on the structure of the set of those convex
functions that are "additive" in this more general sense. In particular, we
show that all operator convex functions are additive for the Werner-Holevo
channel in 3x3 dimensions, which contains the well-known additivity results for
this channel as special cases.Comment: 9 pages, 1 figure. Published versio
Hybrid functionals within the all-electron FLAPW method: implementation and applications of PBE0
We present an efficient implementation of the PBE0 hybrid functional within
the full-potential linearized augmented-plane-wave (FLAPW) method. The
Hartree-Fock exchange term, which is a central ingredient of hybrid
functionals, gives rise to a computationally expensive nonlocal potential in
the one-particle Schroedinger equation. The matrix elements of this exchange
potential are calculated with the help of an auxiliary basis that is
constructed from products of FLAPW basis functions. By representing the Coulomb
interaction in this basis the nonlocal exchange term becomes a Brillouin-zone
(BZ) sum over vector-matrix-vector products. We show that the Coulomb matrix
can be made sparse by a suitable unitary transformation of the auxiliary basis,
which accelerates the computation of the vector-matrix-vector products
considerably. Additionally, we exploit spatial and time-reversal symmetry to
identify the nonvanishing exchange matrix elements in advance and to restrict
the k summations for the nonlocal potential to an irreducible set of k points.
Favorable convergence of the self-consistent-field cycle is achieved by a
nested density-only and density-matrix iteration scheme. We discuss the
convergence with respect to the parameters of our numerical scheme and show
results for a variety of semiconductors and insulators, including oxide
materials, where the PBE0 hybrid functional improves the band gaps and the
description of localized states in comparison with the PBE functional.
Furthermore, we find that in contrast to conventional local
exchange-correlation functionals ferromagnetic EuO is correctly predicted to be
a semiconductor.Comment: 15 pages, 6 figures, 2 table
Current induced rotational torques in the skyrmion lattice phase of chiral magnets
In chiral magnets without inversion symmetry, the magnetic structure can form
a lattice of magnetic whirl lines, a two-dimensional skyrmion lattice,
stabilized by spin-orbit interactions in a small range of temperatures and
magnetic fields. The twist of the magnetization within this phase gives rise to
an efficient coupling of macroscopic magnetic domains to spin currents. We
analyze the resulting spin-transfer effects, and, in particular, focus on the
current induced rotation of the magnetic texture by an angle. Such a rotation
can arise from macroscopic temperature gradients in the system as has recently
been shown experimentally and theoretically. Here we investigate an alternative
mechanism, where small distortions of the skyrmion lattice and the transfer of
angular momentum to the underlying atomic lattice play the key role. We employ
the Landau-Lifshitz-Gilbert equation and adapt the Thiele method to derive an
effective equation of motion for the rotational degree of freedom. We discuss
the dependence of the rotation angle on the orientation of the applied magnetic
field and the distance to the phase transition.Comment: 11 pages, 6 figures; minor changes, published versio
Instability statistics and mixing rates
We claim that looking at probability distributions of \emph{finite time}
largest Lyapunov exponents, and more precisely studying their large deviation
properties, yields an extremely powerful technique to get quantitative
estimates of polynomial decay rates of time correlations and Poincar\'e
recurrences in the -quite delicate- case of dynamical systems with weak chaotic
properties.Comment: 5 pages, 5 figure
Testing spontaneous localization theories with matter-wave interferometry
We propose to test the theory of continuous spontaneous localization (CSL) in
an all-optical time-domain Talbot-Lau interferometer for clusters with masses
exceeding 1000000 amu. By assessing the relevant environmental decoherence
mechanisms, as well as the growing size of the particles relative to the
grating fringes, we argue that it will be feasible to test the quantum
superposition principle in a mass range excluded by recent estimates of the CSL
effect.Comment: 4 pages, 3 figures; corresponds to published versio
CMS-RCNN: Contextual Multi-Scale Region-based CNN for Unconstrained Face Detection
Robust face detection in the wild is one of the ultimate components to
support various facial related problems, i.e. unconstrained face recognition,
facial periocular recognition, facial landmarking and pose estimation, facial
expression recognition, 3D facial model construction, etc. Although the face
detection problem has been intensely studied for decades with various
commercial applications, it still meets problems in some real-world scenarios
due to numerous challenges, e.g. heavy facial occlusions, extremely low
resolutions, strong illumination, exceptionally pose variations, image or video
compression artifacts, etc. In this paper, we present a face detection approach
named Contextual Multi-Scale Region-based Convolution Neural Network (CMS-RCNN)
to robustly solve the problems mentioned above. Similar to the region-based
CNNs, our proposed network consists of the region proposal component and the
region-of-interest (RoI) detection component. However, far apart of that
network, there are two main contributions in our proposed network that play a
significant role to achieve the state-of-the-art performance in face detection.
Firstly, the multi-scale information is grouped both in region proposal and RoI
detection to deal with tiny face regions. Secondly, our proposed network allows
explicit body contextual reasoning in the network inspired from the intuition
of human vision system. The proposed approach is benchmarked on two recent
challenging face detection databases, i.e. the WIDER FACE Dataset which
contains high degree of variability, as well as the Face Detection Dataset and
Benchmark (FDDB). The experimental results show that our proposed approach
trained on WIDER FACE Dataset outperforms strong baselines on WIDER FACE
Dataset by a large margin, and consistently achieves competitive results on
FDDB against the recent state-of-the-art face detection methods
Toxic plants-Detection of colchicine in a fast systematic clinical toxicology screening using liquid chromatography-mass spectrometry
Colchicum autumnale, which can be mistaken for Allium ursinum, contains the alkaloid
colchicine potentially leading to life-threatening up to fatal intoxications. We report
two cases of acute intoxications with unexplained circumstances. Using the authors'
systematic screening approaches, colchicine could be detected in blood plasma and
urine samples using liquid chromatography coupled to linear ion trap mass spectrometry (LC-ITMSn
) and high-resolution tandem mass spectrometry (LC-HRMS/MS).
Metabolites of colchicine could be identified in urine for confirmation of screening
results. Gas chromatography–mass spectrometry (GC-MS) analysis was also conducted, but colchicine could not be detected. Furthermore, colchicine concentration
was estimated via LC-HRMS/MS in plasma samples. Results of the systematic
screening indicated the ingestion of colchicine from both subjects. In both cases, the
parent compound was detected in blood plasma and urine using the LC-HRMS/MS
and LC-ITMSn system. An O-demethylation metabolite was identified in urine
samples of both subjects using LC-HRMS/MS; the N-deacetylation product was also
found in urine samples of both cases via LC-HRMS/MS and LC-ITMSn
. The use of
LC-ITMSn resulted only in the detection of the O-demethylation product in case
2. Plasma concentrations were estimated at 2.5 ng/ml and 4.7 ng/ml for cases 1 and
2, respectively. We demonstrated the detection of this highly toxic alkaloid in blood
plasma and urine using a time-saving and reliable clinical systematic screening.
Furthermore, we identified metabolites of colchicine being rarely discussed in
literature, which can be used as additional screening targets
Nano-wires with surface disorder: Giant localization lengths and dynamical tunneling in the presence of directed chaos
We investigate electron quantum transport through nano-wires with one-sided
surface roughness in the presence of a perpendicular magnetic field.
Exponentially diverging localization lengths are found in the
quantum-to-classical crossover regime, controlled by tunneling between regular
and chaotic regions of the underlying mixed classical phase space. We show that
each regular mode possesses a well-defined mode-specific localization length.
We present analytic estimates of these mode localization lengths which agree
well with the numerical data. The coupling between regular and chaotic regions
can be determined by varying the length of the wire leading to intricate
structures in the transmission probabilities. We explain these structures
quantitatively by dynamical tunneling in the presence of directed chaos.Comment: 15 pages, 12 figure
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