13,159 research outputs found
Entanglement of remote atomic qubits
We report observations of entanglement of two remote atomic qubits, achieved
by generating an entangled state of an atomic qubit and a single photon at Site
A, transmitting the photon to Site B in an adjacent laboratory through an
optical fiber, and converting the photon into an atomic qubit. Entanglement of
the two remote atomic qubits is inferred by performing, locally, quantum state
transfer of each of the atomic qubits onto a photonic qubit and subsequent
measurement of polarization correlations in violation of the Bell inequality
|S| <2. We experimentally determine S =2.16 +/- 0.03. Entanglement of two
remote atomic qubits, each qubit consisting of two independent spin wave
excitations, and reversible, coherent transfer of entanglement between matter
and light, represent important advances in quantum information science.Comment: 5 pages, 3 figure
Coupled cavity QED for coherent control of photon transmission (I): Green function approach for hybrid systems with two-level doping
This is the first one of a series of our papers theoretically studying the
coherent control of photon transmission along the coupled resonator optical
waveguide (CROW) by doping artificial atoms for various hybrid structures. We
will provide the several approaches correspondingly based on Green function,
the mean field method and spin wave theory et al. In the present paper we adopt
the two-time Green function approach to study the coherent transmission photon
in a CROW with homogeneous couplings, each cavity of which is doped by a
two-level artificial atom. We calculate the two-time correlation function for
photon in the weak-coupling case. Its poles predict the exact dispersion
relation, which results in the group velocity coherently controlled by the
collective excitation of the doping atoms. We emphasize the role of the
population inversion of doping atoms induced by some polarization mechanism.Comment: 11 pages, 9 figure
Evolutionary tracks for Betelgeuse
We have constructed a series of non-rotating quasi-hydrostatic evolutionary
models for the M2 Iab supergiant Betelgeuse (). Our models are
constrained by multiple observed values for the temperature, luminosity,
surface composition and mass loss for this star, along with the parallax
distance and high resolution imagery that determines its radius. We have then
applied our best-fit models to analyze the observed variations in surface
luminosity and the size of detected surface bright spots as the result of
up-flowing convective material from regions of high temperature in the surface
convective zone. We also attempt to explain the intermittently observed
periodic variability in a simple radial linear adiabatic pulsation model. Based
upon the best fit to all observed data, we suggest a best progenitor mass
estimate of and a current age from the start of the
zero-age main sequence of Myr based upon the observed ejected mass
while on the giant branch.Comment: 27 pages, 11 figures, Revised per referee suggestions, Accepted for
publication in the Astrophysical Journa
Influence of surface passivation on ultrafast carrier dynamics and terahertz radiation generation in GaAs
The carrier dynamics of photoexcited electrons in the vicinity of the surface
of (NH4)2S-passivated GaAs were studied via terahertz (THz) emission
spectroscopy and optical-pump THz-probe spectroscopy. THz emission spectroscopy
measurements, coupled with Monte Carlo simulations of THz emission, revealed
that the surface electric field of GaAs reverses after passivation. The
conductivity of photoexcited electrons was determined via optical-pump
THz-probe spectroscopy, and was found to double after passivation. These
experiments demonstrate that passivation significantly reduces the surface
state density and surface recombination velocity of GaAs. Finally, we have
demonstrated that passivation leads to an enhancement in the power radiated by
photoconductive switch THz emitters, thereby showing the important influence of
surface chemistry on the performance of ultrafast THz photonic devices.Comment: 4 pages, 3 figures, to appear in Applied Physics Letter
Spectral analysis of Gene co-expression network of Zebrafish
We analyze the gene expression data of Zebrafish under the combined framework
of complex networks and random matrix theory. The nearest neighbor spacing
distribution of the corresponding matrix spectra follows random matrix
predictions of Gaussian orthogonal statistics. Based on the eigenvector
analysis we can divide the spectra into two parts, first part for which the
eigenvector localization properties match with the random matrix theory
predictions, and the second part for which they show deviation from the theory
and hence are useful to understand the system dependent properties. Spectra
with the localized eigenvectors can be characterized into three groups based on
the eigenvalues. We explore the position of localized nodes from these
different categories. Using an overlap measure, we find that the top
contributing nodes in the different groups carry distinguished structural
features. Furthermore, the top contributing nodes of the different localized
eigenvectors corresponding to the lower eigenvalue regime form different
densely connected structure well separated from each other. Preliminary
biological interpretation of the genes, associated with the top contributing
nodes in the localized eigenvectors, suggests that the genes corresponding to
same vector share common features.Comment: 6 pages, four figures (accepted in EPL
Deflection of Slow Light by Magneto-Optically Controlled Atomic Media
We present a semi-classical theory for light deflection by a coherent
-type three-level atomic medium in an inhomogeneous magnetic field or
an inhomogeneous control laser. When the atomic energy levels (or the Rabi
coupling by the control laser) are position-dependent due to the Zeeman effect
by the inhomogeneous magnetic field (or the inhomogeneity of the control field
profile), the spatial dependence of the refraction index of the atomic medium
will result in an observable deflection of slow signal light when the
electromagnetically induced transparency happens to avoid medium absorption.
Our theoretical approach based on Fermat's principle in geometrical optics not
only provides a consistent explanation for the most recent experiment in a
straightforward way, but also predicts the new effects for the slow signal
light deflection by the atomic media in an inhomogeneous off-resonant control
laser field.Comment: 4 pages, 3 figure
Leukemia-related chromosomal loss detected in hematopoietic progenitor cells of benzene-exposed workers.
Benzene exposure causes acute myeloid leukemia and hematotoxicity, shown as suppression of mature blood and myeloid progenitor cell numbers. As the leukemia-related aneuploidies monosomy 7 and trisomy 8 previously had been detected in the mature peripheral blood cells of exposed workers, we hypothesized that benzene could cause leukemia through the induction of these aneuploidies in hematopoietic stem and progenitor cells. We measured loss and gain of chromosomes 7 and 8 by fluorescence in situ hybridization in interphase colony-forming unit-granulocyte-macrophage (CFU-GM) cells cultured from otherwise healthy benzene-exposed (n=28) and unexposed (n=14) workers. CFU-GM monosomy 7 and 8 levels (but not trisomy) were significantly increased in subjects exposed to benzene overall, compared with levels in the control subjects (P=0.0055 and P=0.0034, respectively). Levels of monosomy 7 and 8 were significantly increased in subjects exposed to <10 p.p.m. (20%, P=0.0419 and 28%, P=0.0056, respectively) and ≥ 10 p.p.m. (48%, P=0.0045 and 32%, 0.0354) benzene, compared with controls, and significant exposure-response trends were detected (P(trend)=0.0033 and 0.0057). These data show that monosomies 7 and 8 are produced in a dose-dependent manner in the blood progenitor cells of workers exposed to benzene, and may be mechanistically relevant biomarkers of early effect for benzene and other leukemogens
A study of acute respiratory disease in families exposed to different levels of Air pollution in the Great Salt Lake basin, Utah, 1971-1972 and 1972-1973.
The reported incidence of acute respiratory illness in families exposed to different concentrations of air pollution was studied during two consecutive school years. The purpose of the study was to determine the effect of increased exposure to sulfur dioxide and suspended particulate matter. In each of four study communities, the mothers of approximately 250 white families were contacted biweekly to obtain information regarding the occurrence of respiratory symptoms in each family member. Annual mean ambient sulfur dioxide concentrations in one community for the three years included in the study (1971-1973) were well above the current air quality standard of 80 micrograms/m3, while in the other three communities the annual sulfur dioxide concentrations were much lower (usually less than 40 micrograms/m3). Suspended particulate matter concentrations in high sulfur dioxide community were close to the limit designated by the annual standard (75 micrograms/m3) but actual exposures in the four communities probably were not excessive. Regression analyses of the data collected showed inconsistent associations between illness rates and educational attainment of the head of household, crowding in the home, bronchitis in parents or smoking of parents. However, once the effects of these factors were removed the adjusted rates showed little association with community of residence. It was concluded that the higher concentrations of sulfur dioxide in the Utah atmosphere could not be the cause of increases in acute respiratory illness in the exposed populations
Probing the magnetic ground state of the molecular Dysprosium triangle
We present zero field muon spin lattice relaxation measurements of a
Dysprosium triangle molecular magnet. The local magnetic fields sensed by the
implanted muons indicate the coexistence of static and dynamic internal
magnetic fields below K. Bulk magnetization and heat capacity
measurements show no indication of magnetic ordering below this temperature. We
attribute the static fields to the slow relaxation of the magnetization in the
ground state of Dy3. The fluctuation time of the dynamic part of the field is
estimated to be ~0.55 s at low temperaturesComment: 5 pages, 5 figures, accepted for publication in Phys. Rev.
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