8,350 research outputs found
Quantum Tomography
This is the draft version of a review paper which is going to appear in
"Advances in Imaging and Electron Physics"Comment: To appear in "Advances in Imaging and Electron Physics". Some figs
with low resolutio
No-reference image quality assessment through the von Mises distribution
An innovative way of calculating the von Mises distribution (VMD) of image
entropy is introduced in this paper. The VMD's concentration parameter and some
fitness parameter that will be later defined, have been analyzed in the
experimental part for determining their suitability as a image quality
assessment measure in some particular distortions such as Gaussian blur or
additive Gaussian noise. To achieve such measure, the local R\'{e}nyi entropy
is calculated in four equally spaced orientations and used to determine the
parameters of the von Mises distribution of the image entropy. Considering
contextual images, experimental results after applying this model show that the
best-in-focus noise-free images are associated with the highest values for the
von Mises distribution concentration parameter and the highest approximation of
image data to the von Mises distribution model. Our defined von Misses fitness
parameter experimentally appears also as a suitable no-reference image quality
assessment indicator for no-contextual images.Comment: 29 pages, 11 figure
Creation, storage, and on-demand release of optical quantum states with a negative Wigner function
Highly nonclassical quantum states of light, characterized by Wigner
functions with negative values, have been created so far only in a heralded
fashion. In this case, the desired output emerges rarely and randomly from a
quantum-state generator. An important example is the heralded production of
high-purity single-photon states, typically based on some nonlinear optical
interaction. In contrast, on-demand single-photon sources were also reported,
exploiting the quantized level structure of matter systems. These sources,
however, lead to highly impure output states, composed mostly of vacuum. While
such impure states may still exhibit certain single-photon-like features such
as anti-bunching, they are not enough nonclassical for advanced quantum
information processing. On the other hand, the intrinsic randomness of pure,
heralded states can be circumvented by first storing and then releasing them on
demand. Here we propose such a controlled release, and we experimentally
demonstrate it for heralded single photons. We employ two optical cavities,
where the photons are both created and stored inside one cavity, and finally
released through a dynamical tuning of the other cavity. We demonstrate storage
times of up to 300 ns, while keeping the single-photon purity around 50% after
storage. This is the first demonstration of a negative Wigner function at the
output of an on-demand photon source or a quantum memory. In principle, our
storage system is compatible with all kinds of nonclassical states, including
those known to be essential for many advanced quantum information protocols.Comment: 14 pages, 5 figure
Quantum homodyne tomography with a priori constraints
I present a novel algorithm for reconstructing the Wigner function from
homodyne statistics. The proposed method, based on maximum-likelihood
estimation, is capable of compensating for detection losses in a numerically
stable way.Comment: 4 pages, REVTeX, 2 figure
The estimation of geoacoustic properties from broadband acoustic data, focusing on instantaneous frequency techniques
The compressional wave velocity and attenuation of marine sediments are fundamental to marine science. In order to obtain reliable estimates of these parameters it is necessary to examine in situ acoustic data, which is generally broadband. A variety of techniques for estimating the compressional wave velocity and attenuation from broadband acoustic data are reviewed. The application of Instantaneous Frequency (IF) techniques to data collected from a normal-incidence chirp profiler is examined. For the datasets examined the best estimates of IF are obtained by dividing the chirp profile into a series of sections, estimating the IF of each trace in the section using the first moments of the Wigner Ville distribution, and stacking the resulting IF to obtain a composite IF for the section. As the datasets examined cover both gassy and saturated sediments, this is likely to be the optimum technique for chirp datasets collected from all sediment environments
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