29,190 research outputs found
Overview of the Status and Strangeness Capabilities of STAR
STAR is a large acceptance spectrometer capable of precision measurements of
a wide variety of strange particles. We discuss the STAR detector, its
configuration during the first two years of RHIC operation, and its initial
performance for Au+Au collisions. The expected performance for strangeness
physics and initial data on strange particle reconstruction in Au+Au collisions
are presented.Comment: Proceedings of the Fifth International Conference on Strangeness in
Quark Matter, Berkeley, California, July 20-25, 200
Heralded Two-Photon Entanglement from Probabilistic Quantum Logic Operations on Multiple Parametric Down-Conversion Sources
An ideal controlled-NOT gate followed by projective measurements can be used
to identify specific Bell states of its two input qubits. When the input qubits
are each members of independent Bell states, these projective measurements can
be used to swap the post-selected entanglement onto the remaining two qubits.
Here we apply this strategy to produce heralded two-photon polarization
entanglement using Bell states that originate from independent parametric
down-conversion sources, and a particular probabilistic controlled-NOT gate
that is constructed from linear optical elements. The resulting implementation
is closely related to an earlier proposal by Sliwa and Banaszek
[quant-ph/0207117], and can be intuitively understood in terms of familiar
quantum information protocols. The possibility of producing a ``pseudo-demand''
source of two-photon entanglement by storing and releasing these heralded pairs
from independent cyclical quantum memory devices is also discussed.Comment: 5 pages, 4 figures; submitted to IEEE Journal of Selected Topics in
Quantum Electronics, special issue on "Quantum Internet Technologies
Study of information transfer optimization for communication satellites
The results are presented of a study of source coding, modulation/channel coding, and systems techniques for application to teleconferencing over high data rate digital communication satellite links. Simultaneous transmission of video, voice, data, and/or graphics is possible in various teleconferencing modes and one-way, two-way, and broadcast modes are considered. A satellite channel model including filters, limiter, a TWT, detectors, and an optimized equalizer is treated in detail. A complete analysis is presented for one set of system assumptions which exclude nonlinear gain and phase distortion in the TWT. Modulation, demodulation, and channel coding are considered, based on an additive white Gaussian noise channel model which is an idealization of an equalized channel. Source coding with emphasis on video data compression is reviewed, and the experimental facility utilized to test promising techniques is fully described
Floppy modes and the free energy: Rigidity and connectivity percolation on Bethe Lattices
We show that negative of the number of floppy modes behaves as a free energy
for both connectivity and rigidity percolation, and we illustrate this result
using Bethe lattices. The rigidity transition on Bethe lattices is found to be
first order at a bond concentration close to that predicted by Maxwell
constraint counting. We calculate the probability of a bond being on the
infinite cluster and also on the overconstrained part of the infinite cluster,
and show how a specific heat can be defined as the second derivative of the
free energy. We demonstrate that the Bethe lattice solution is equivalent to
that of the random bond model, where points are joined randomly (with equal
probability at all length scales) to have a given coordination, and then
subsequently bonds are randomly removed.Comment: RevTeX 11 pages + epsfig embedded figures. Submitted to Phys. Rev.
Investigation of a single-photon source based on quantum interference
We report on an experimental investigation of a single-photon source based on
a quantum interference effect first demonstrated by Koashi, Matsuoka, and
Hirano [Phys. Rev. A 53, 3621 (1996)]. For certain types of measurement-based
quantum information processing applications this technique may be useful as a
high rate, but random, source of single photons.Comment: Submitted to the New J. Phys. Focus Issue on "Measurement-based
quantum information processing
Spin transport in a unitary Fermi gas close to the BCS transition
We consider spin transport in a two-component ultracold Fermi gas with
attractive interspecies interactions close to the BCS pairing transition. In
particular, we consider the spin-transport relaxation rate and the
spin-diffusion constant. Upon approaching the transition, the scattering
amplitude is enhanced by pairing fluctuations. However, as the system
approaches the transition, the spectral weight for excitations close to the
Fermi level is decreased by the formation of a pseudogap. To study the
consequence of these two competing effects, we determine the spin-transport
relaxation rate and the spin-diffusion constant using both a Boltzmann approach
and a diagrammatic approach. The former ignores pseudogap physics and finite
lifetime effects. In the latter, we incorporate the full pseudogap physics and
lifetime effects, but we ignore vertex corrections, so that we effectively
calculate single-particle relaxation rates instead of transport relaxation
rates. We find that there is qualitative agreement between these two approaches
although the results for the transport coefficients differ quantitatively.Comment: 9 pages, 10 figure
Affective iconic words benefit from additional sound–meaning integration in the left amygdala
Recent studies have shown that a similarity between sound and meaning of a word (i.e., iconicity) can help more readily access the meaning of that word, but the neural mechanisms underlying this beneficial role of iconicity in semantic processing remain largely unknown. In an fMRI study, we focused on the affective domain and examined whether affective iconic words (e.g., high arousal in both sound and meaning) activate additional brain regions that integrate emotional information from different domains (i.e., sound and meaning). In line with our hypothesis, affective iconic words, compared to their non‐iconic counterparts, elicited additional BOLD responses in the left amygdala known for its role in multimodal representation of emotions. Functional connectivity analyses revealed that the observed amygdalar activity was modulated by an interaction of iconic condition and activations in two hubs representative for processing sound (left superior temporal gyrus) and meaning (left inferior frontal gyrus) of words. These results provide a neural explanation for the facilitative role of iconicity in language processing and indicate that language users are sensitive to the interaction between sound and meaning aspect of words, suggesting the existence of iconicity as a general property of human language
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