2,410 research outputs found
Transfer of Nonclassical Properties from A Microscopic Superposition to Macroscopic Thermal States in The High Temperature Limit
We present several examples where prominent quantum properties are
transferred from a microscopic superposition to thermal states at high
temperatures. Our work is motivated by an analogy of Schrodinger's cat paradox,
where the state corresponding to the virtual cat is a mixed thermal state with
a large average photon number. Remarkably, quantum entanglement can be produced
between thermal states with nearly the maximum Bell-inequality violation even
when the temperatures of both modes approach infinity.Comment: minor corrections, acknowledgments added, Phys.Rev.Lett., in pres
Experimental Violation of Bell's Inequality in Spatial-Parity Space
We report the first experimental violation of Bell's inequality in the
spatial domain using the Einstein--Podolsky--Rosen state. Two-photon states
generated via optical spontaneous parametric downconversion are shown to be
entangled in the parity of their one-dimensional transverse spatial profile.
Superpositions of Bell states are prepared by manipulation of the optical
pump's transverse spatial parity--a classical parameter. The Bell-operator
measurements are made possible by devising simple optical arrangements that
perform rotations in the one-dimensional spatial-parity space of each photon of
an entangled pair and projective measurements onto a basis of even--odd
functions. A Bell-operator value of 2.389 +- 0.016 is recorded, a violation of
the inequality by more than 24 standard deviations.Comment: 10 pages, 3 figures, 1 Tabl
Evidence for continuing current in sprite-producing cloud-to-ground lightning
Includes bibliographical references (page 3642).Radio atmospherics launched by sprite producing positive cloud-to-ground lightning flashes and observed at Palmer Station, Antarctica, exhibit large ELF slow tails following the initial VLF portion, indicating the presence of continuing currents in the source lightning flashes. One-to-one correlation of sferics with NLDN lightning data in both time and arrival azimuth, measured with an accuracy of ±1° at ~12,000 km range, allows unambiguous identification of lightning flashes originating in the storm of interest. Slow-tail measurements at Palmer can potentially be used to measure continuing currents in lightning flashes over nearly half of the Earth's surface
Mechanism of ELF radiation from sprites
Includes bibliographical references (page 3496).Charge and current systems associated with sprites constitute a part of the large scale atmospheric electric circuit, providing a context for physical understanding of recently discovered ELF radiation originating from currents flowing within the body of sprites. It is shown that the impulse of the electric current driven in the conducting body of the sprite by lightning generated transient quasi-electrostatic fields produces significant electromagnetic radiation in the ELF range of frequencies, comparable to that radiated by the causative lightning discharge
An Outbreak of Community-Acquired Foodborne Illness Caused by Methicillin-Resistant Staphylococcus aureus
Infections with methicillin-resistant Staphylococcus aureus (MRSA) are increasingly community acquired. We investigated an outbreak in which a food handler, food specimen, and three ill patrons were culture positive for the same toxin-producing strain of MRSA. This is the first report of an outbreak of gastrointestinal illness caused by community-acquired MRSA
Quantum superpositions and entanglement of thermal states at high temperatures and their applications to quantum-information processing
We study characteristics of superpositions and entanglement of thermal states at high temperatures and discuss their applications to quantum-information processing. We introduce thermal-state qubits and thermal-Bell states, which are a generalization of pure-state qubits and Bell states to thermal mixtures. A scheme is then presented to discriminate between the four thermal-Bell states without photon number resolving detection but with Kerr nonlinear interactions and two single-photon detectors. This enables one to perform quantum teleportation and gate operations for quantum computation with thermal-state qubits
Quantifying Kinematic Substructure in the Milky Way's Stellar Halo
We present and analyze the positions, distances, and radial velocities for
over 4000 blue horizontal-branch (BHB) stars in the Milky Way's halo, drawn
from SDSS DR8. We search for position-velocity substructure in these data, a
signature of the hierarchical assembly of the stellar halo. Using a cumulative
"close pair distribution" (CPD) as a statistic in the 4-dimensional space of
sky position, distance, and velocity, we quantify the presence of
position-velocity substructure at high statistical significance among the BHB
stars: pairs of BHB stars that are close in position on the sky tend to have
more similar distances and radial velocities compared to a random sampling of
these overall distributions. We make analogous mock-observations of 11
numerical halo formation simulations, in which the stellar halo is entirely
composed of disrupted satellite debris, and find a level of substructure
comparable to that seen in the actually observed BHB star sample. This result
quantitatively confirms the hierarchical build-up of the stellar halo through a
signature in phase (position-velocity) space. In detail, the structure present
in the BHB stars is somewhat less prominent than that seen in most simulated
halos, quite possibly because BHB stars represent an older sub-population. BHB
stars located beyond 20 kpc from the Galactic center exhibit stronger
substructure than at kpc.Comment: 29 page, 10 figures, 1 table; accepted by APJ; for related article by
another group see arXiv:1011.192
Mapping the stellar structure of the Milky Way thick disk and halo using SEGUE photometry
We map the stellar structure of the Galactic thick disk and halo by applying
color-magnitude diagram (CMD) fitting to photometric data from the SEGUE
survey, allowing, for the first time, a comprehensive analysis of their
structure at both high and low latitudes using uniform SDSS photometry.
Incorporating photometry of all relevant stars simultaneously, CMD fitting
bypasses the need to choose single tracer populations. Using old stellar
populations of differing metallicities as templates we obtain a sparse 3D map
of the stellar mass distribution at |Z|>1 kpc. Fitting a smooth Milky Way model
comprising exponential thin and thick disks and an axisymmetric power-law halo
allows us to constrain the structural parameters of the thick disk and halo.
The thick-disk scale height and length are well constrained at 0.75+-0.07 kpc
and 4.1+-0.4 kpc, respectively. We find a stellar halo flattening within ~25
kpc of c/a=0.88+-0.03 and a power-law index of 2.75+-0.07 (for 7<R_{GC}<~30
kpc). The model fits yield thick-disk and stellar halo densities at the solar
location of rho_{thick,sun}=10^{-2.3+-0.1} M_sun pc^{-3} and
rho_{halo,sun}=10^{-4.20+-0.05} M_sun pc^{-3}, averaging over any
substructures. Our analysis provides the first clear in situ evidence for a
radial metallicity gradient in the Milky Way's stellar halo: within R<~15 kpc
the stellar halo has a mean metallicity of [Fe/H]=-1.6, which shifts to
[Fe/H]=-2.2 at larger radii. Subtraction of the best-fit smooth and symmetric
model from the overall density maps reveals a wealth of substructures at all
latitudes, some attributable to known streams and overdensities, and some new.
A simple warp cannot account for the low latitude substructure, as
overdensities occur simultaneously above and below the Galactic plane.
(abridged)Comment: 13 pages, 10 figures, accepted for publication in Astrophysical
Journa
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