2,697 research outputs found
Dependence of the decoherence of polarization states in phase-damping channels on the frequency spectrum envelope of photons
We consider the decoherence of photons suffering in phase-damping channels.
By exploring the evolutions of single-photon polarization states and two-photon
polarization-entangled states, we find that different frequency spectrum
envelopes of photons induce different decoherence processes. A white frequency
spectrum can lead the decoherence to an ideal Markovian process. Some color
frequency spectrums can induce asymptotical decoherence, while, some other
color frequency spectrums can make coherence vanish periodically with variable
revival amplitudes. These behaviors result from the non-Markovian effects on
the decoherence process, which may give rise to a revival of coherence after
complete decoherence.Comment: 7 pages, 4 figures, new results added, replaced by accepted versio
A Fair and Secure Cluster Formation Process for Ad Hoc Networks
An efficient approach for organizing large ad hoc networks is to divide the nodes
into multiple clusters and designate, for each cluster, a clusterhead which is responsible for
holding intercluster control information. The role of a clusterhead entails rights and duties.
On the one hand, it has a dominant position in front of the others because it manages the
connectivity and has access to other nodeÂżs sensitive information. But on the other hand, the
clusterhead role also has some associated costs. Hence, in order to prevent malicious nodes
from taking control of the group in a fraudulent way and avoid selfish attacks from suitable
nodes, the clusterhead needs to be elected in a secure way. In this paper we present a novel
solution that guarantees the clusterhead is elected in a cheat-proof manner
Cavity QED treatment of scattering-induced efficient free-space excitation and collection in high-Q whispering-gallery microcavities
Whispering-gallery microcavity laser possesses ultralow threshold, whereas
convenient free-space optical excitation and collection suffer from low
efficiencies due to its rotational symmetry. Here we analytically study a
three-dimensional microsphere coupled to a nano-sized scatterer in the
framework of quantum optics. It is found that the scatterer is capable of
coupling light in and out of the whispering-gallery modes (WGMs) without
seriously degrading their high-Q properties, while the microsphere itself plays
the role of a lens to focus the input beam on the scatterer and vice versa. Our
analytical results show that (1) the high-Q WGMs can be excited in free space,
and (2) over 50% of the microcavity laser emission can be collected within less
than . This coupling system holds great potential for low
threshold microlasers free of external couplers.Comment: 10 pages, 8 figure
Strongly enhanced light-matter interaction in a hybrid photonic-plasmonic resonator
We propose a hybrid photonic-plasmonic resonant structure which consists of a
metal nanoparticle (MNP) and a whispering gallery mode (WGM) microcavity. It is
found that the hybrid mode enables a strong interaction between the light and
matter, and the single-atom cooperativity is enhanced by more than two orders
of magnitude compared to that in a bare WGM microcavity. This remarkable
improvement originates from two aspects: (1) the MNP offers a highly enhanced
local field in the vicinity of an emitter, and (2), surprisingly, the
high-\textit{Q} property of WGMs can be maintained in the presence of the MNP.
Thus the present system has great advantages over a single microcavity or a
single MNP, and holds great potential in quantum optics, nonlinear optics and
highly sensitive biosening.Comment: 5 pages, 4 figure
Effects of space flight factors on genetic diversity of Buchloe dactyloides seeds
The objective of this research was to investigate the effects of space flight factors on Buchloe dactyloides âJingyin No.3â seeds. After the retrieval, basic turf characters of plants were tested. Among the 100 plants tested, 21 showed great change on phenotype characters, including leaf blade length and width, height, stem diameter, number of tillers, number and length of stolon, length of stolon inter node, leaf color and extent of leaf turning yellow. 33 primers were screened in inter-simple sequence repeats (ISSR) analysis to evaluate DNA variation between mutations and their ground controls. Results show that 15.6 reliable bands were generated by 7 primers, of which 12.9 (80.9%) were polymorphic. Based on the study, we can conclude that the space flight factors could induce inheritable mutagenic changes on B. dactyloides seeds, and do further research to demonstrate these changes in genetic material of the mutants.Key words: Genetic diversity, Buchloe dactyloides, spaceflight, inter-simple sequence repeats
Coupling of a Single Diamond Nanocrystal to a Whispering-Gallery Microcavity: Photon Transportation Benefitting from Rayleigh Scattering
We study the Rayleigh scattering induced by a diamond nanocrystal in a
whispering-gallery-microcavity--waveguide coupling system, and find that it
plays a significant role in the photon transportation. On one hand, this study
provides a new insight into future solid-state cavity quantum electrodynamics
toward strong coupling physics. On the other hand, benefitting from this
Rayleigh scattering, novel photon transportation such as dipole induced
transparency and strong photon antibunching can occur simultaneously. As
potential applications, this system can function as high-efficiency photon
turnstiles. In contrast to [B. Dayan \textit{et al.}, \textrm{Science}
\textbf{319},1062 (2008)], the photon turnstiles proposed here are highly
immune to nanocrystal's azimuthal position.Comment: 4 pages, 4 figure
Structural analysis of ferromagnetic Mn-doped ZnO thin films deposited by radio frequency magnetron sputtering
We report on the structural analysis of ferromagnetic Mn-doped ZnO thin films deposited by radio frequency magnetron sputtering, using transmission electron microscopy (TEM), high-resolution x-ray diffraction, and Rutherford backscattering spectroscopy (RBS) measurements. The ferromagnetic Mn-doped ZnO film showed magnetization hysteresis at 5 and 300 K. A TEM analysis revealed that the Mn-doped ZnO included a high density of round-shaped cubic and elongated hexagonal MnZn oxide precipitates. The incorporation of Mn caused a large amount of structural disorder in the crystalline columnar ZnO lattice, although the wurtzite crystal structure was maintained. The observed ferromagnetism is discussed based on the structural characteristics indicated by TEM and the behavior of Mn when it is substituted into a ZnO lattice derived from RBS measurements
Data-driven generation of 4D velocity profiles in the aneurysmal ascending aorta
Numerical simulations of blood flow are a valuable tool to investigate the
pathophysiology of ascending thoracic aortic aneurysms (ATAA). To accurately
reproduce hemodynamics, computational fluid dynamics (CFD) models must employ
realistic inflow boundary conditions (BCs). However, the limited availability
of in vivo velocity measurements still makes researchers resort to idealized
BCs. In this study we generated and thoroughly characterized a large dataset of
synthetic 4D aortic velocity profiles suitable to be used as BCs for CFD
simulations. 4D flow MRI scans of 30 subjects with ATAA were processed to
extract cross-sectional planes along the ascending aorta, ensuring spatial
alignment among all planes and interpolating all velocity fields to a reference
configuration. Velocity profiles of the clinical cohort were extensively
characterized by computing flow morphology descriptors of both spatial and
temporal features. By exploiting principal component analysis (PCA), a
statistical shape model (SSM) of 4D aortic velocity profiles was built and a
dataset of 437 synthetic cases with realistic properties was generated.
Comparison between clinical and synthetic datasets showed that the synthetic
data presented similar characteristics as the clinical population in terms of
key morphological parameters. The average velocity profile qualitatively
resembled a parabolic-shaped profile, but was quantitatively characterized by
more complex flow patterns which an idealized profile would not replicate.
Statistically significant correlations were found between PCA principal modes
of variation and flow descriptors. We built a data-driven generative model of
4D aortic velocity profiles, suitable to be used in computational studies of
blood flow. The proposed software system also allows to map any of the
generated velocity profiles to the inlet plane of any virtual subject given its
coordinate set.Comment: 21 pages, 5 figures, 2 tables To be submitted to "Computer methods
and programs in biomedicine" Scripts: https://github.com/saitta-s/flow4D
Synthetic velocity profiles: //doi.org/10.5281/zenodo.725198
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