715 research outputs found
Chronicles of Oklahoma
Article explores the history of the Civilian Conservation Corps in Tulsa and Oklahoma City. The Corps, formed as a part of New Deal relief labor programs, developed three urban parks in the area
Chronicles of Oklahoma
Article chronicles what life was like inside of the Cherokee Nation before the Civil War. The article focuses on how tribe members interacted with authority figures, mission schools, architecture, and finances
Chronicles of Oklahoma
Article chronicles the creation and history of the Civilian Conservation Corps in Oklahoma. The program was created during the first hundred days of President Franklin D. Roosevelt's New Deal as a means to protect the conservation of parks and camps
On quantum teleportation with beam-splitter-generated entanglement
Following the lead of Cochrane, Milburn, and Munro [Phys. Rev. A {\bf 62},
062307 (2000)], we investigate theoretically quantum teleportation by means of
the number-sum and phase-difference variables. We study Fock-state entanglement
generated by a beam splitter and show that two-mode Fock-state inputs can be
entangled by a beam splitter into close approximations of maximally entangled
eigenstates of the phase difference and the photon-number sum
(Einstein-Podolsky-Rosen -- EPR -- states). Such states could be experimentally
feasible with on-demand single-photon sources. We show that the teleportation
fidelity can reach near unity when such ``quasi-EPR'' states are used as the
quantum channel.Comment: 7 pages (two-column), 7 figures, submitted to Phys. Rev. A. Text
unmodified, postscript error correcte
No-cloning theorem and teleportation criteria for quantum continuous variables
We discuss the criteria presently used for evaluating the efficiency of
quantum teleportation schemes for continuous variables. Using an argument based
upon the difference between 1-to-2 quantum cloning (quantum duplication) and
1-to-infinity cloning (classical measurement), we show that a fidelity value
larger than 2/3 is required for successful quantum teleportation of coherent
states. This value has not been reached experimentally so far.Comment: 4 pages, 1 figure, submitted to Phys. Rev.
Quantum correlated twin atomic beams via photo-dissociation of a molecular Bose-Einstein condensate
We study the process of photo-dissociation of a molecular Bose-Einstein
condensate as a potential source of strongly correlated twin atomic beams. We
show that the two beams can possess nearly perfect quantum squeezing in their
relative numbers.Comment: Corrected LaTeX file layou
Stable nondegenerate optical parametric oscillation at degenerate frequencies in Na:KTP
We report the realization of a light source specifically designed for the
generation of bright continuous-variable entangled beams and for
Heisenberg-limited inteferometry. The source is a nondegenerate, single-mode,
continuous-wave optical parametric oscillator in Na:KTP, operated at frequency
degeneracy and just above threshold, which is also of interest for the study of
critical fluctuations at the transition point. The residual
frequency-difference jitter is 150 kHz for a 3 MHz cold cavity half-width
at half maximum. We observe 4 dB of photon-number-difference squeezing at 200
kHz. The Na:KTP crystal is noncritically phase-matched for a 532 nm pump and
polarization crosstalk is therefore practically nonexistent
Distances and ages of globular clusters using Hipparcos parallaxes of local subdwarfs
We discuss the impact of Population II and Globular Cluster (GCs) stars on
the derivation of the age of the Universe, and on the study of the formation
and early evolution of galaxies, our own in particular. The long-standing
problem of the actual distance scale to Population II stars and GCs is
addressed, and a variety of different methods commonly used to derive distances
to Population II stars are briefly reviewed. Emphasis is given to the
discussion of distances and ages for GCs derived using Hipparcos parallaxes of
local subdwarfs. Results obtained by different authors are slightly different,
depending on different assumptions about metallicity scale, reddenings, and
corrections for undetected binaries. These and other uncertainties present in
the method are discussed. Finally, we outline progress expected in the near
future.Comment: Invited review article to appear in: `Post-Hipparcos Cosmic Candles',
A. Heck & F. Caputo (Eds), Kluwer Academic Publ., Dordrecht, in press. 22
pages including 3 tables and 2 postscript figures, uses Kluwer's crckapb.sty
LaTeX style file, enclose
Brown dwarfs and very low mass stars in the Praesepe open cluster: a dynamically unevolved mass function?
[Abridged] In this paper, we present the results of a photometric survey to
identify low mass and brown dwarf members of the old open cluster Praesepe (age
of 590[+150][-120]Myr and distance of 190[+6.0][-5.8]pc) and use this to infer
its mass function which we compare with that of other clusters. We have
performed an optical (Ic-band) and near-infrared (J and Ks-band) photometric
survey of Praesepe with a spatial coverage of 3.1deg^2. With 5sigma detection
limits of Ic=23.4 and J=20.0, our survey is sensitive to objects with masses
from about 0.6 to 0.05Msol. The mass function of Praesepe rises from 0.6Msol
down to 0.1Msol and then turns-over at ~0.1Msol. The rise observed is in
agreement with the mass function derived by previous studies, including a
survey based on proper motion and photometry. Comparing our mass function with
that for another open cluster with a similar age, the Hyades (age ~ 600Myr), we
see a significant difference. Possible reasons are that dynamical evaporation
has not influenced the Hyades and Praesepe in the same way, or that the
clusters did not have the same initial mass function, or that dynamical
interactions have modified the evolution of one or both clusters. Although a
difference in the binary fractions of the clusters could cause the observed
(i.e. system) mass functions to differ, measurements in the literature give no
evidence for a significant difference in the binary fractions of the two
clusters. Of our cluster candidates, six have masses predicted to be equal to
or below the stellar/substellar boundary at 0.072Msol.Comment: 11 pages, 11 figures, accepted for publication in A&A. Higher
resolution of Figures 2-3-4-5 in A&A published version. Revised version
corrected for Englis
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