20,653 research outputs found
Universal measurement of quantum correlations of radiation
A measurement technique is proposed which, in principle, allows one to
observe the general space-time correlation properties of a quantized radiation
field. Our method, called balanced homodyne correlation measurement, unifies
the advantages of balanced homodyne detection with those of homodyne
correlation measurements.Comment: 4 pages, 4 figures, small misprints were corrected, accepted to Phys.
Rev. Let
L- and K-band LMSS propagation measurements using MARECS-B, OLYMPUS, and ACTS
L-band measurements of land mobile satellite systems (LMSS) propagation effects were last made at the end of 1988, but some voids were left in the database, making modeling of low elevation roadside tree shadowing and multipath reflections difficult for some path geometries. Transmission of a pilot tone from MARECS-B at 55 deg West during Sep. and Dec. 1991 gave an opportunity to fill the gaps in the experimental results. Two campaigns during which fade data were obtained at elevation angles from 7 deg to 40 deg are described. Below 15 deg, specular terrain reflections in a non-shadowing, hilly environment were observed to introduce significant fading. Although the reflecting surface was at a distance of up to several km, it is shown that the reflected signals are delayed by less than 1 microsec. Mobile measurements were also attempted receiving the 20 GHz Olympus beacon, but antenna pointing problems restricted first results to straight-line driving
Mobile satellite propagation measurements and modeling: A review of results for systems engineers
An overview of Mobile Satellite System (MSS) propagation measurements and modeling is given, including a summary of results. The simple models presented should be of some use to systems engineers. A complete summary of propagation experiments with literature references is included
Mass Hierarchy Resolution in Reactor Anti-neutrino Experiments: Parameter Degeneracies and Detector Energy Response
Determination of the neutrino mass hierarchy using a reactor neutrino
experiment at 60 km is analyzed. Such a measurement is challenging due to
the finite detector resolution, the absolute energy scale calibration, as well
as the degeneracies caused by current experimental uncertainty of . The standard method is compared with a proposed Fourier
transformation method. In addition, we show that for such a measurement to
succeed, one must understand the non-linearity of the detector energy scale at
the level of a few tenths of percent.Comment: 7 pages, 6 figures, accepted by PR
NASA Workshop on future directions in surface modeling and grid generation
Given here is a summary of the paper sessions and panel discussions of the NASA Workshop on Future Directions in Surface Modeling and Grid Generation held a NASA Ames Research Center, Moffett Field, California, December 5-7, 1989. The purpose was to assess U.S. capabilities in surface modeling and grid generation and take steps to improve the focus and pace of these disciplines within NASA. The organization of the workshop centered around overviews from NASA centers and expert presentations from U.S. corporations and universities. Small discussion groups were held and summarized by group leaders. Brief overviews and a panel discussion by representatives from the DoD were held, and a NASA-only session concluded the meeting. In the NASA Program Planning Session summary there are five recommended steps for NASA to take to improve the development and application of surface modeling and grid generation
Waveguide QED: Many-Body Bound State Effects on Coherent and Fock State Scattering from a Two-Level System
Strong coupling between a two-level system (TLS) and bosonic modes produces
dramatic quantum optics effects. We consider a one-dimensional continuum of
bosons coupled to a single localized TLS, a system which may be realized in a
variety of plasmonic, photonic, or electronic contexts. We present the exact
many-body scattering eigenstate obtained by imposing open boundary conditions.
Multi-photon bound states appear in the scattering of two or more photons due
to the coupling between the photons and the TLS. Such bound states are shown to
have a large effect on scattering of both Fock and coherent state wavepackets,
especially in the intermediate coupling strength regime. We compare the
statistics of the transmitted light with a coherent state having the same mean
photon number: as the interaction strength increases, the one-photon
probability is suppressed rapidly, and the two- and three-photon probabilities
are greatly enhanced due to the many-body bound states. This results in
non-Poissonian light.Comment: 10 page
Locating the source of projectile fluid droplets
The ill-posed projectile problem of finding the source height from spattered
droplets of viscous fluid is a longstanding obstacle to accident reconstruction
and crime scene analysis. It is widely known how to infer the impact angle of
droplets on a surface from the elongation of their impact profiles. However,
the lack of velocity information makes finding the height of the origin from
the impact position and angle of individual drops not possible. From aggregate
statistics of the spatter and basic equations of projectile motion, we
introduce a reciprocal correlation plot that is effective when the polar launch
angle is concentrated in a narrow range. The vertical coordinate depends on the
orientation of the spattered surface, and equals the tangent of the impact
angle for a level surface. When the horizontal plot coordinate is twice the
reciprocal of the impact distance, we can infer the source height as the slope
of the data points in the reciprocal correlation plot. If the distribution of
launch angles is not narrow, failure of the method is evident in the lack of
linear correlation. We perform a number of experimental trials, as well as
numerical calculations and show that the height estimate is insensitive to
aerodynamic drag. Besides its possible relevance for crime investigation,
reciprocal-plot analysis of spatter may find application to volcanism and other
topics and is most immediately applicable for undergraduate science and
engineering students in the context of crime-scene analysis.Comment: To appear in the American Journal of Physics (ms 23338). Improved
readability and organization in this versio
Caging dynamics in a granular fluid
We report an experimental investigation of the caging motion in a uniformly
heated granular fluid, for a wide range of filling fractions, . At low
the classic diffusive behavior of a fluid is observed. However, as
is increased, temporary cages develop and particles become increasingly
trapped by their neighbors. We statistically analyze particle trajectories and
observe a number of robust features typically associated with dense molecular
liquids and colloids. Even though our monodisperse and quasi-2D system is known
to not exhibit a glass transition, we still observe many of the precursors
usually associated with glassy dynamics. We speculate that this is due to a
process of structural arrest provided, in our case, by the presence of
crystallization.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Let
Quantum-state input-output relations for absorbing cavities
The quantized electromagnetic field inside and outside an absorbing high-
cavity is studied, with special emphasis on the absorption losses in the
coupling mirror and their influence on the outgoing field. Generalized operator
input-output relations are derived, which are used to calculate the Wigner
function of the outgoing field. To illustrate the theory, the preparation of
the outgoing field in a Schr\"{o}dinger cat-like state is discussed.Comment: 12 pages, 5 eps figure
Leaky cavities with unwanted noise
A phenomenological approach is developed that allows one to completely
describe the effects of unwanted noise, such as the noise associated with
absorption and scattering, in high-Q cavities. This noise is modeled by a block
of beam splitters and an additional input-output port. The replacement schemes
enable us to formulate appropriate quantum Langevin equations and input-output
relations. It is demonstrated that unwanted noise renders it possible to
combine a cavity input mode and the intracavity mode in a nonmonochromatic
output mode. Possible applications to unbalanced and cascaded homodyning of the
intracavity mode are discussed and the advantages of the latter method are
shown.Comment: 13 pages, 7 figures; published versio
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