1,436 research outputs found
Quantum repeaters with individual rare-earth ions at telecommunication wavelengths
We present a quantum repeater scheme that is based on individual erbium and
europium ions. Erbium ions are attractive because they emit photons at
telecommunication wavelength, while europium ions offer exceptional spin
coherence for long-term storage. Entanglement between distant erbium ions is
created by photon detection. The photon emission rate of each erbium ion is
enhanced by a microcavity with high Purcell factor, as has recently been
demonstrated. Entanglement is then transferred to nearby europium ions for
storage. Gate operations between nearby ions are performed using dynamically
controlled electric-dipole coupling. These gate operations allow entanglement
swapping to be employed in order to extend the distance over which entanglement
is distributed. The deterministic character of the gate operations allows
improved entanglement distribution rates in comparison to atomic ensemble-based
protocols. We also propose an approach that utilizes multiplexing in order to
enhance the entanglement distribution rate.Comment: 13 pages, 4 figure
Chaos Near to the Critical Point: Butterfly Effect and Pole-Skipping
We study the butterfly effect and pole-skipping phenomenon for the 1RCBH
model which enjoys a critical point in its phase diagram. Using the holographic
idea, we compute the butterfly velocity and interestingly find that this
velocity can probe the critical behavior of this model. We calculate the
dynamical exponent of this quantity near the critical point and find a perfect
agreement with the value of the other quantity's dynamical exponent near this
critical point. We also find that at chaos point, the phenomenon of
pole-skipping appears which is a sign of a multivalued retarded correlation
function. We briefly address the butterfly velocity and pole-skipping for the
AdS-RN black hole solution which on its boundary a strongly coupled charged
field theory lives. For both of these models, we find at each
point of parameter space where is the speed of sound wave propagation.Comment: 27 pages, 1 figuer
Feature Classification for Robust Shape-Based Collaborative Tracking and Model Updating
Abstract A new collaborative tracking approach is introduced which takes advantage of classified features. The core of this tracker is a single tracker that is able to detect occlusions and classify features contributing in localizing the object. Features are classified in four classes: good, suspicious, malicious, and neutral. Good features are estimated to be parts of the object with a high degree of confidence. Suspicious ones have a lower, yet significantly high, degree of confidence to be a part of the object. Malicious features are estimated to be generated by clutter, while neutral features are characterized with not a sufficient level of uncertainty to be assigned to the tracked object. When there is no occlusion, the single tracker acts alone, and the feature classification module helps it to overcome distracters such as still objects or little clutter in the scene. When more than one desired moving objects bounding boxes are close enough, the collaborative tracker is activated and it exploits the advantages of the classified features to localize each object precisely as well as updating the objects shape models more precisely by assigning again the classified features to the objects. The experimental results show successful tracking compared with the collaborative tracker that does not use the classified features. Moreover, more precise updated object shape models will be shown
On flood risk pooling in Europe
In this paper, we review and discuss some challenges in insuring flood risk in Europe on the national level, including high correlation of damages. Making use of recent advances in extreme value theory, we, furthermore, model flood risk with heavy-tailed distributions and their truncated counterparts and apply the discussed techniques to an inflation- and building-value-adjusted annual data set of flood losses in Europe. The analysis leads to Value-at-Risk estimates for individual countries and for Europe as a whole, allowing to quantify the diversification potential for flood risk in Europe. Finally, we identify optimal risk pooling possibilities in case a joint insurance strategy on the European level cannot be realized and quantify the resulting inefficiency in terms of additional necessary solvency capital. Thus, the results also contribute to the ongoing discussion on how public risk transfer mechanisms can supplement missing private insurance coverage
Joint Communication and Sensing in RIS-enabled mmWave Networks
Empowering cellular networks with augmented sensing capabilities is one of
the key research areas in 6G communication systems. Recently, we have witnessed
a plethora of efforts to devise solutions that integrate sensing capabilities
into communication systems, i.e., joint communication and sensing (JCAS).
However, most prior works do not consider the impact of reconfigurable
intelligent surfaces (RISs) on JCAS systems, especially at millimeter-wave
(mmWave) bands. Given that RISs are expected to become an integral part of
cellular systems, it is important to investigate their potential in cellular
networks beyond communication goals. In this paper, we study mmWave orthogonal
frequency-division multiplexing (OFDM) JCAS systems in the presence of RISs.
Specifically, we jointly design the hybrid beamforming and RIS phase shifts to
guarantee the sensing functionalities via minimizing a chordal-distance metric,
subject to signal-to-interference-plus-noise (SINR) and power constraints. The
non-convexity of the investigated problem poses a challenge which we address by
proposing a solution based on the penalty method and manifold-based alternating
direction method of multipliers (ADMM). Simulation results demonstrate that
under various settings both sensing and communication experience improved
performance when the RIS is adequately designed. In addition, we discuss the
tradeoff between sensing and communication
Surface sampling within a pediatric ward—how multiple factors affect cleaning efficacy
BACKGROUND: The objectives of this study were to assess the number of organisms present on different surfaces within a clinical environment before and after cleaning took place, and to identify the impact of cleaning. The study involved extensive 2-week microbiological environmental monitoring of an entire ward before and after cleaning; the ward was located within a pediatric hematology-oncology ward comprised of a day unit and outpatient ward. METHODS: Tryptone soya agar contact plates were used to take a total of 1,160 surface samples before and after cleaning from 55 predetermined sites. Samples were taken from representative surfaces throughout the ward representing a variety of materials, surface heights, functions, and distances from patients, as well as both high-touch and infrequently touched surfaces. RESULTS: After surface cleaning was undertaken within the ward, there was a significant difference between the amount of colony-forming units (CFUs) recovered before and after cleaning (P < .0001). Cleaning produced an average CFU reduction of 68% throughout the ward environment. The corridor was the most contaminated area within the ward. There were differences in the CFUs among the various areas within the ward, which were cleaned with varying efficiency. The surface material, who interacted with the surface, levels of initial contamination, perceived risk, and perceived cleanability were all found to have a varying impact on the cleaning effectiveness. CONCLUSIONS: To the authors' current knowledge, this is the only study to assess cleaning within a pediatric ward by taking samples directly before and after cleaning. The standard of cleaning undertaken within the ward is open for discussion, and these data highlight the need for an improved cleaning intervention and can provide insight into the multitude of factors that must be considered when designing an effective training protocol
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