4,539 research outputs found
Quantum Noise in Multipixel Image Processing
We consider the general problem of the quantum noise in a multipixel
measurement of an optical image. We first give a precise criterium in order to
characterize intrinsic single mode and multimode light. Then, using a
transverse mode decomposition, for each type of possible linear combination of
the pixels' outputs we give the exact expression of the detection mode, i.e.
the mode carrying the noise. We give also the only way to reduce the noise in
one or several simultaneous measurements.Comment: 8 pages and 1 figur
Synchronization of Sound Sources
Sound generation and -interaction is highly complex, nonlinear and
self-organized. Already 150 years ago Lord Rayleigh raised the following
problem: Two nearby organ pipes of different fundamental frequencies sound
together almost inaudibly with identical pitch. This effect is now understood
qualitatively by modern synchronization theory (M. Abel et al., J. Acoust. Soc.
Am., 119(4), 2006). For a detailed, quantitative investigation, we substituted
one pipe by an electric speaker. We observe that even minute driving signals
force the pipe to synchronization, thus yielding three decades of
synchronization -- the largest range ever measured to our knowledge.
Furthermore, a mutual silencing of the pipe is found, which can be explained by
self-organized oscillations, of use for novel methods of noise abatement.
Finally, we develop a specific nonlinear reconstruction method which yields a
perfect quantitative match of experiment and theory.Comment: 5 pages, 4 figure
Three-Nucleon Continuum by means of the Hyperspherical Adiabatic Method
This paper investigates the possible use of the Hyperspherical Adiabatic
basis in the description of scattering states of a three-body system. In
particular, we analyze a 1+2 collision process below the three-body breakup.
The convergence patterns for the observables of interest are analyzed by
comparison to a unitary equivalent Hyperspherical Harmonic expansion.
Furthermore, we compare and discuss two different possible choices for
describing the asymptotic configurations of the system, related to the use of
Jacobi or hyperspherical coordinates. In order to illustrate the difficulties
and advantages of the approach two simple numerical applications are shown in
the case of neutron-deuteron scattering at low energies using s-wave
interactions. We found that the optimization driven by the Hyperspherical
Adiabatic basis is not as efficient for scattering states as in bound state
applications.Comment: 29 pages, 5 figures, accepted for publication in Few-Body Systems (in
press
Optimality Theory as a Framework for Lexical Acquisition
This paper re-investigates a lexical acquisition system initially developed
for French.We show that, interestingly, the architecture of the system
reproduces and implements the main components of Optimality Theory. However, we
formulate the hypothesis that some of its limitations are mainly due to a poor
representation of the constraints used. Finally, we show how a better
representation of the constraints used would yield better results
Twin polaritons in semiconductor microcavities
The quantum correlations between the beams generated by polariton pair
scattering in a semiconductor microcavity above the parametric oscillation
threshold are computed analytically. The influence of various parameters like
the cavity-exciton detuning, the intensity mismatch between the signal and
idler beams and the amount of spurious noise is analyzed. We show that very
strong quantum correlations between the signal and idler polaritons can be
achieved. The quantum effects on the outgoing light fields are strongly reduced
due to the large mismatch in the coupling of the signal and idler polaritons to
the external photons
Conditional preparation of a quantum state in the continuous variable regime: generation of a sub-Poissonian state from twin beams
We report the first experimental demonstration of conditional preparation of
a non classical state of light in the continuous variable regime. Starting from
a non degenerate OPO which generates above threshold quantum intensity
correlated signal and idler "twin beams", we keep the recorded values of the
signal intensity only when the idler falls inside a band of values narrower
than its standard deviation. By this very simple technique, we generate a
sub-Poissonian state 4.4dB below shot noise from twin beams exhibiting 7.5dB of
noise reduction in the intensity difference.Comment: 4 pages, Accepted in Phys. Rev. Let
Residual Symmetries in the Spectrum of Periodically Driven Alkali Rydberg States
We identify a fundamental structure in the spectrum of microwave driven
alkali Rydberg states, which highlights the remnants of the Coulomb symmetry in
the presence of a non-hydrogenic core. Core-induced corrections with respect to
the hydrogen spectrum can be accounted for by a perturbative approach.Comment: 7 pages, 2 figures, to be published in Europhysics Letter
Characterizing Quantum Properties of a Measurement Apparatus: Insights from the Retrodictive Approach
Using the retrodictive approach of quantum physics, we show that the state
retrodicted from the response of a measurement apparatus is a convenient tool
to fully characterize its quantum properties. We translate in terms of this
state some interesting aspects of the quantum behavior of a detector, such as
the non-classicality or the non-gaussian character of its measurements. We also
introduce estimators - the projectivity, the ideality, the fidelity or the
detectivity of measurements perfomed by the apparatus - which directly follow
from the retrodictive approach. Beyond their fundamental significance for
describing general quantum measurements, these properties are crucial in
several protocols, in particular in the conditional preparation of
non-classical states of light or in measurement-driven quantum information
processing
Non-perturbative Gluons and Pseudoscalar Mesons in Baryon Spectroscopy
We study baryon spectroscopy including the effects of pseudoscalar meson
exchange and one gluon exchange potentials between quarks, governed by
. The non-perturbative, hyperspherical method calculations show that
one can obtain a good description of the data by using a quark-meson coupling
constant that is compatible with the measured pion-nucleon coupling constant,
and a reasonably small value of .Comment: 12 pages; Submitted to Phys. Rev. C. Rapid Communication
Nano-displacement measurements using spatially multimode squeezed light
We demonstrate the possibility of surpassing the quantum noise limit for
simultaneous multi-axis spatial displacement measurements that have zero mean
values. The requisite resources for these measurements are squeezed light beams
with exotic transverse mode profiles. We show that, in principle, lossless
combination of these modes can be achieved using the non-degenerate Gouy phase
shift of optical resonators. When the combined squeezed beams are measured with
quadrant detectors, we experimentally demonstrate a simultaneous reduction in
the transverse x- and y- displacement fluctuations of 2.2 dB and 3.1 dB below
the quantum noise limit.Comment: 21 pages, 9 figures, submitted to "Special Issue on Fluctuations &
Noise in Photonics & Quantum Optics" of J. Opt.
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