38,001 research outputs found
Nonlinear photon transport in a semiconductor waveguide-cavity system containing a single quantum dot: Anharmonic cavity-QED regime
We present a semiconductor master equation technique to study the
input/output characteristics of coherent photon transport in a semiconductor
waveguide-cavity system containing a single quantum dot. We use this approach
to investigate the effects of photon propagation and anharmonic cavity-QED for
various dot-cavity interaction strengths, including weakly-coupled,
intermediately-coupled, and strongly-coupled regimes. We demonstrate that for
mean photon numbers much less than 0.1, the commonly adopted weak excitation
(single quantum) approximation breaks down, even in the weak coupling regime.
As a measure of the anharmonic multiphoton-correlations, we compute the Fano
factor and the correlation error associated with making a semiclassical
approximation. We also explore the role of electron--acoustic-phonon scattering
and find that phonon-mediated scattering plays a qualitatively important role
on the light propagation characteristics. As an application of the theory, we
simulate a conditional phase gate at a phonon bath temperature of K in the
strong coupling regime.Comment: To appear in PR
Current status of MCNP6 as a simulation tool useful for space and accelerator applications
For the past several years, a major effort has been undertaken at Los Alamos
National Laboratory (LANL) to develop the transport code MCNP6, the latest LANL
Monte-Carlo transport code representing a merger and improvement of MCNP5 and
MCNPX. We emphasize a description of the latest developments of MCNP6 at higher
energies to improve its reliability in calculating rare-isotope production,
high-energy cumulative particle production, and a gamut of reactions important
for space-radiation shielding, cosmic-ray propagation, and accelerator
applications. We present several examples of validation and verification of
MCNP6 compared to a wide variety of intermediate- and high-energy experimental
data on reactions induced by photons, mesons, nucleons, and nuclei at energies
from tens of MeV to about 1 TeV/nucleon, and compare to results from other
modern simulation tools.Comment: 4 pages, 3 figures, Proc. 11th Conference on the Intersections of
Particle and Nuclear Physics (CIPANP 2012), St. Petersburg, FL, May 28 - June
3, 201
Phonon-dressed Mollow triplet in the regime of cavity-QED
We study the resonance fluorescence spectra of a driven quantum dot placed
inside a high semiconductor cavity and interacting with an acoustic phonon
bath. The dynamics is calculated using a time-convolutionless master equation
obtained in the polaron frame. We demonstrate pronounced spectral broadening of
the Mollow sidebands through cavity-emission which, for small cavity-coupling
rates, increases quadratically with the Rabi frequency. However, for larger
cavity coupling rates, this broadening dependence is found to be more complex.
This field-dependent Mollow triplet broadening is primarily a consequence of
the triplet peaks sampling different parts of the asymmetric phonon bath, and
agrees directly with recent experiments with semiconductor micropillars. The
influence from the detuned cavity photon bath and multi-photon effects is shown
to play a qualitatively important role on the fluorescence spectra.Comment: 4 pages, 4 figure
Daylight quantum key distribution over 1.6 km
Quantum key distribution (QKD) has been demonstrated over a point-to-point
-km atmospheric optical path in full daylight. This record
transmission distance brings QKD a step closer to surface-to-satellite and
other long-distance applications.Comment: 4 pages, 2 figures, 1 table. Submitted to PRL on 14 January 2000 for
publication consideratio
Practical free-space quantum key distribution over 1 km
A working free-space quantum key distribution (QKD) system has been developed
and tested over an outdoor optical path of ~1 km at Los Alamos National
Laboratory under nighttime conditions. Results show that QKD can provide secure
real-time key distribution between parties who have a need to communicate
secretly. Finally, we examine the feasibility of surface to satellite QKD.Comment: 5 pages, 2 figures, 2 tables. Submitted to Physics Review Letters,
May 199
The twisted fourth moment of the Riemann zeta function
We compute the asymptotics of the fourth moment of the Riemann zeta function
times an arbitrary Dirichlet polynomial of length Comment: 28 pages. v2: added reference
Extreme times in financial markets
We apply the theory of continuous time random walks to study some aspects of
the extreme value problem applied to financial time series. We focus our
attention on extreme times, specifically the mean exit time and the mean
first-passage time. We set the general equations for these extremes and
evaluate the mean exit time for actual data.Comment: 6 pages, 3 figure
Local atomic structure and discommensurations in the charge density wave of CeTe3
The local structure of CeTe3 in the incommensurate charge density wave
(IC-CDW) state has been obtained using atomic pair distribution function (PDF)
analysis of x-ray diffraction data. Local atomic distortions in the Te-nets due
to the CDW are larger than observed crystallographically, resulting in distinct
short and long Te-Te bonds. Observation of different distortion amplitudes in
the local and average structures are explained by the discommensurated nature
of the CDW since the PDF is sensitive to the local displacements within the
commensurate regions whereas the crystallographic result averages over many
discommensurated domains. The result is supported by STM data. This is the
first quantitative local structural study within the commensurate domains in an
IC-CDW system.Comment: 4 pages, 4 figure
Enhanced dielectrophoresis of nanocolloids by dimer formation
We investigate the dielectrophoretic motion of charge-neutral, polarizable
nanocolloids through molecular dynamics simulations. Comparison to analytical
results derived for continuum systems shows that the discrete charge
distributions on the nanocolloids have a significant impact on their coupling
to the external field. Aggregation of nanocolloids leads to enhanced
dielectrophoretic transport, provided that increase in the dipole moment upon
aggregation can overcome the related increase in friction. The dimer
orientation and the exact structure of the nanocolloid charge distribution are
shown to be important in the enhanced transport
350 Micron Dust Emission from High Redshift Objects
We report observations of a sample of high redshift sources (1.8<z<4.7),
mainly radio-quiet quasars, at 350 microns using the SHARC bolometer camera at
the Caltech Submillimeter Observatory. Nine sources were detected (>4-sigma)
and upper limits were obtained for 11 with 350 micron flux density limits
(3-sigma) in the range 30-125mJy. Combining published results at other
far-infrared and millimeter wavelengths with the present data, we are able to
estimate the temperature of the dust, finding relatively low values, averaging
50K. From the spectral energy distribution, we derive dust masses of a few 10^8
M_sun and luminosities of 4-33x10^{12} L_sun (uncorrected for any
magnification) implying substantial star formation activity. Thus both the
temperature and dust masses are not very different from those of local
ultraluminous infrared galaxies. For this redshift range, the 350 micron
observations trace the 60-100 micron rest frame emission and are thus directly
comparable with IRAS studies of low redshift galaxies.Comment: 5 pages, 2 PS figures. Accepted for publication in Astrophysical
Journal Letter
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