1,642 research outputs found
Photon polarization entanglement induced by biexciton: experimental evidence for violation of Bell's inequality
We have investigated the polarization entanglement between photon pairs
generated from a biexciton in a CuCl single crystal via resonant hyper
parametric scattering. The pulses of a high repetition pump are seen to provide
improved statistical accuracy and the ability to test Bell's inequality. Our
results clearly violate the inequality and thus manifest the quantum
entanglement and nonlocality of the photon pairs. We also analyzed the quantum
state of our photon pairs using quantum state tomography.Comment: 4 pages, 5 figure
Quantum diffraction and interference of spatially correlated photon pairs and its Fourier-optical analysis
We present one- and two-photon diffraction and interference experiments
involving parametric down-converted photon pairs. By controlling the divergence
of the pump beam in parametric down-conversion, the diffraction-interference
pattern produced by an object changes from a quantum (perfectly correlated)
case to a classical (uncorrelated) one. The observed diffraction and
interference patterns are accurately reproduced by Fourier-optical analysis
taking into account the quantum spatial correlation. We show that the relation
between the spatial correlation and the object size plays a crucial role in the
formation of both one- and two-photon diffraction-interference patterns.Comment: 10 pages, 13 figures, rev.
Can the Steep Mass Profile of A1689 Be Explained by a Triaxial Dark Halo?
The steep mass profile of A1689 derived from recent detailed lensing
observations is not readily reconciled with the low concentration halos
predicted by the standard CDM model. However, halo triaxiality may act to bias
the profile constraints derived assuming a spherically symmetric mass
distribution, since lensing relates only to the projected mass distribution. A
degree of halo triaxiality is inherent to the CDM structure formation, arising
from the collision-less nature of the dark matter. Here we compare the
CDM-based model predictions of triaxial halo with the precise lensing
measurements of A1689 based on the ACS/HST and Subaru data, over a wide range
of 10kpc<r<2Mpc. The model lensing profiles cover the intrinsic spread of halo
mass and shape, and are projected over all inclinations when comparing with the
data. We show that the model parameters are only weakly constrained and
strongly degenerate mainly because of the lack of information along the line of
sight. In particular, the limits on the concentration parameter become less
restrictive with increasing triaxiality. Yet, by comparing the obtained
constraints with expected probability distributions for the axis ratio and
concentration parameters computed from numerical simulations, we find that ~6%
of cluster-size halos in the CDM model can match the A1689 lensing observations
at the 2-sigma level, corresponding to cases where the major-axis of the halo
is aligned with the line of sight. Thus halo triaxiality could reduce the
apparent discrepancy between theory and observation. This hypothesis needs to
be further explored by a statistical lensing study for other clusters as well
as by complementary three-dimensional information derived using X-ray,
kinematics, and SZ effect observations.Comment: 7 pages, 6 figures, accepted for publication in Ap
Four-Photon Quantum Interferometry at a Telecom Wavelength
We report the experimental demonstration of four-photon quantum interference
using telecom-wavelength photons. Realization of multi-photon quantum
interference is essential to linear optics quantum information processing and
measurement-based quantum computing. We have developed a source that
efficiently emits photon pairs in a pure spectrotemporal mode at a telecom
wavelength region, and have demonstrated the quantum interference exhibiting
the reduced fringe intervals that correspond to the reduced de Broglie
wavelength of up to the four photon `NOON' state. Our result should open a path
to practical quantum information processing using telecom-wavelength photons.Comment: 4 pages, 4 figure
Strong Turbulence in the Cool Cores of Galaxy Clusters: Can Tsunamis Solve the Cooling Flow Problem?
Based on high-resolution two-dimensional hydrodynamic simulations, we show
that the bulk gas motions in a cluster of galaxies, which are naturally
expected during the process of hierarchical structure formation of the
universe, have a serous impact on the core. We found that the bulk gas motions
represented by acoustic-gravity waves create local but strong turbulence, which
reproduces the complicated X-ray structures recently observed in cluster cores.
Moreover, if the wave amplitude is large enough, they can suppress the
radiative cooling of the cores. Contrary to the previous studies, the heating
is operated by the turbulence, not weak shocks. The turbulence could be
detected in near-future space X-ray missions such as ASTRO-E2.Comment: Movies are available at http://th.nao.ac.jp/tsunami/index.ht
HCN to HCO^+ Millimeter Line Diagnostics of AGN Molecular Torus I : Radiative Transfer Modeling
We explore millimeter line diagnostics of an obscuring molecular torus
modeled by a hydrodynamic simulation with three-dimensional nonLTE radiative
transfer calculations. Based on the results of high-resolution hydrodynamic
simulation of the molecular torus around an AGN, we calculate intensities of
HCN and HCO^{+} rotational lines as two representative high density tracers.
The three-dimensional radiative transfer calculations shed light on a
complicated excitation state in the inhomogeneous torus, even though a
spatially uniform chemical structure is assumed. Our results suggest that HCN
must be much more abundant than HCO^{+} in order to obtain a high ratio
() observed in some of the nearby galaxies. There is a
remarkable dispersion in the relation between integrated intensity and column
density, indicative of possible shortcomings of HCN(1-0) and HCO^{+}(1-0) lines
as high density tracers. The internal structures of the inhomogeneous molecular
torus down to subparsec scale in external galaxies will be revealed by the
forthcoming Atacama Large Millimeter/submillimeter Array (ALMA). The
three-dimensional radiative transfer calculations of molecular lines with
high-resolution hydrodynamic simulation prove to be a powerful tool to provide
a physical basis for molecular line diagnostics of the central regions of
external galaxies.Comment: 29 pages, 13 figures, Accepted for publication in ApJ, For high
resolution figures see http://alma.mtk.nao.ac.jp/~masako/MS72533v2.pd
Three Dimensional Simulation of Gamma Ray Emission from Asymmetric Supernovae and Hypernovae
Hard X- and -ray spectra and light curves resulting from radioactive
decays are computed for aspherical (jet-like) and energetic supernova models
(representing a prototypical hypernova SN 1998bw), using a 3D energy- and
time-dependent Monte Carlo scheme. The emission is characterized by (1) early
emergence of high energy emission, (2) large line-to-continuum ratio, and (3)
large cut-off energy by photoelectric absorptions in hard X-ray energies. These
three properties are not sensitively dependent on the observer's direction. On
the other hand, fluxes and line profiles depend sensitively on the observer's
direction, showing larger luminosity and larger degree of blueshift for an
observer closer to the polar () direction. Strategies to derive the degree
of asphericity and the observer's direction from (future) observations are
suggested on the basis of these features, and an estimate on detectability of
the high energy emission by the {\it INTEGRAL} and future observatories is
presented. Also presented is examination on applicability of a gray effective
-ray opacity for computing the energy deposition rate in the aspherical
SN ejecta. The 3D detailed computations show that the effective -ray
opacity cm g reproduces the
detailed energy-dependent transport for both spherical and aspherical
(jet-like) geometry.Comment: 24 pages, 13 figures. Figure 7 added in the accepted version. ApJ,
644 (01 June 2006 issue), in press. Resolution of figures lower than the
published versio
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