1,145 research outputs found
Extremal Quantum Correlations and Cryptographic Security
We investigate a fundamental property of device independent security in
quantum cryptography by characterizing probability distributions which are
necessarily independent of the measurement results of any eavesdropper. We show
that probability distributions that are secure in this sense are exactly the
extremal quantum probability distributions. This allows us to give a
characterization of security in algebraic terms. We apply the method to common
examples for two-party as well as multi-party setups and present a scheme for
verifying security of probability distributions with two parties, two
measurement settings, and two outcomes.Comment: 7 pages, 2 figures, revised version, accepted for publication in
Phys. Rev. Let
Pericardial biopsy and fenestration
Employing a video thoracoscopic pericardial fenestration constitutes a promising technique for the investigation and treatment of chronic pericardial effusions. It combines the benefit of low invasiveness with the advantages of open biopsy. The procedure simultaneously allows both an accurate diagnosis under visual control (inspection, aspiration, well targeted biopsy of pathological processes) and the performance of effective therapeutic intervention. Without imposing unacceptable stress, it also facilitates rapid symptom relief in patients with advanced malignant disease whose general condition is severely impaire
Continuous Variable Quantum Key Distribution: Finite-Key Analysis of Composable Security against Coherent Attacks
We provide a security analysis for continuous variable quantum key
distribution protocols based on the transmission of squeezed vacuum states
measured via homodyne detection. We employ a version of the entropic
uncertainty relation for smooth entropies to give a lower bound on the number
of secret bits which can be extracted from a finite number of runs of the
protocol. This bound is valid under general coherent attacks, and gives rise to
keys which are composably secure. For comparison, we also give a lower bound
valid under the assumption of collective attacks. For both scenarios, we find
positive key rates using experimental parameters reachable today.Comment: v2: new author, technical inaccuracy corrected, new plots, v3:
substantially improved key rates against coherent attacks (due to correction
of an error in the numerical computation
Implementation of Quantum Key Distribution with Composable Security Against Coherent Attacks using Einstein-Podolsky-Rosen Entanglement
Secret communication over public channels is one of the central pillars of a
modern information society. Using quantum key distribution (QKD) this is
achieved without relying on the hardness of mathematical problems which might
be compromised by improved algorithms or by future quantum computers.
State-of-the-art QKD requires composable security against coherent attacks for
a finite number of samples. Here, we present the first implementation of QKD
satisfying this requirement and additionally achieving security which is
independent of any possible flaws in the implementation of the receiver. By
distributing strongly Einstein-Podolsky-Rosen entangled continuous variable
(CV) light in a table-top arrangement, we generated secret keys using a highly
efficient error reconciliation algorithm. Since CV encoding is compatible with
conventional optical communication technology, we consider our work to be a
major promotion for commercialized QKD providing composable security against
the most general channel attacks.Comment: 7 pages, 3 figure
Momentum-resolved electron-phonon interaction in lead determined by neutron resonance spin-echo spectroscopy
Neutron resonance spin-echo spectroscopy was used to monitor the temperature
evolution of the linewidths of transverse acoustic phonons in lead across the
superconducting transition temperature, , over an extended range of the
Brillouin zone. For phonons with energies below the superconducting energy gap,
a linewidth reduction of maximum amplitude eV was observed below
. The electron-phonon contribution to the phonon lifetime extracted from
these data is in satisfactory overall agreement with {\it ab-initio}
lattice-dynamical calculations, but significant deviations are found
Optimality of entropic uncertainty relations
The entropic uncertainty relation proven by Maassen and Uffink for arbitrary
pairs of two observables is known to be non-optimal. Here, we call an
uncertainty relation optimal, if the lower bound can be attained for any value
of either of the corresponding uncertainties. In this work we establish optimal
uncertainty relations by characterising the optimal lower bound in scenarios
similar to the Maassen-Uffink type. We disprove a conjecture by Englert et al.
and generalise various previous results. However, we are still far from a
complete understanding and, based on numerical investigation and analytical
results in small dimension, we present a number of conjectures.Comment: 24 pages, 10 figure
EC87-160 Musk Thistle....Its Appearance, Spread and Control
Extension circular 87-160 is about musk thistle, its appearance, spread and control
A selective view of climatological data and likelihood estimation
This article gives a narrative overview of what constitutes climatological data and their typical features, with a focus on aspects relevant to statistical modeling. We restrict the discussion to univariate spatial fields and focus on maximum likelihood estimation. To address the problem of enormous datasets, we study three common approximation schemes: tapering, direct misspecification, and composite likelihood for Gaussian and nonGaussian distributions. We focus particularly on the so-called 'sinh-arcsinh distribution', obtained through a specific transformation of the Gaussian distribution. Because it has flexible marginal distributions - possibly skewed and/or heavy-tailed - it has a wide range of applications. One appealing property of the transformation involved is the existence of an explicit inverse transformation that makes likelihood-based methods straightforward. We describe a simulation study illustrating the effects of the different approximation schemes. To the best of our knowledge, a direct comparison of tapering, direct misspecification, and composite likelihood has never been made previously, and we show that direct misspecification is inferior. In some metrics, composite likelihood has a minor advantage over tapering. We use the estimation approaches to model a high-resolution global climate change field. All simulation code is available as a Docker container and is thus fully reproducible. Additionally, the present article describes where and how to get various climate datasets. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND licens
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