Search results for "methods"
showing 10 items of 4526 documents
Two-dimensional temporal coherence coding for super resolved imaging
2009
In this paper, we present an approach that can be used for transmission of 2D spatial information through space-limited systems capable of transmitting even only a single spatial pixel. The input 2D object is illuminated with temporally incoherent illumination. The axial coherence length is very short and it equals only a few microns. Attached to the input object spatial random phase mask generates different axial shift for every pixel of the input. The temporal delays of the encoding (axial shifts) of every pixel are longer than the coherence length of the illuminating source. Therefore no temporal correlation exists between the various pixels of the input. A lens combines all spatial pixe…
Towards an Understanding of the Dynamics of the Milky Way
2005
Determination of outer rotation curve using Galactic masers The rotation curve of the Galaxy is poorly determined outside the solar circle (e.g. Honma & Sofue 1997). The situation makes difficult to derive the dynamical mass of the Galaxy, which is essential for inferring the amount of Galactic dark gravitating matter. We selected Galactic masers in this study since they distributed over the whole Galaxy. Moreover, they can observed with VLBI at extremely high angular resolution, allowing a measurement of the annual parallax, and thus the source’s distance, and its proper motion due to Galactic rotation with phase referencing VLBI astrometric observation. We have already performed phase-ref…
The FIGARO II experiment: a general outline of the mission and the principal scientific results
1992
The FIGARO II (French Italian Gamma-Ray Observatory) experiment has been launched successfully three times: in July 1986 from Milo (Trapani), in November 1988 from Charleville (Australia) and in July 1990 again from Milo. In the first flight the observational program was limited to the Crab pulsar PSR0531+21 only because of a telemetry failure: the high sensitivity of FIGARO II allowed an accurate study of the pulse shape as well as a phase-resolved spectroscopy. It was also possible to evaluate the dispersion measure of the Crab pulsar at the flight date from the time delay between gamma-ray and radio pulses. The major results of the second flight were a stringent upper limit to the low-en…
Distillation of entanglement between distant systems by repeated measurements on an entanglement mediator
2004
A recently proposed purification method, in which the Zeno-like measurements of a subsystem can bring about a distillation of another subsystem in interaction with the former, is utilized to yield entangled states between distant systems. It is shown that the measurements of a two-level system locally interacting with other two spatially separated not coupled subsystems, can distill entangled states from the latter irrespectively of the initial states of the two subsystems.
Nonadiabatic quantum search algorithms
2007
7 pages, 4 figures.-- PACS nrs.: 03.67.Lx, 05.45.Mt, 72.15.Rn.-- ISI Article Identifier: 000251326400049.-- ArXiv pre-print available at: http://arxiv.org/abs/0706.1139
Tomographic approach to the violation of Bell's inequalities for quantum states of two qutrits
2009
The tomographic method is employed to investigate the presence of quantum correlations in two classes of parameter-dependent states of two qutrits. The violation of some Bell's inequalities in a wide domain of the parameter space is shown. A comparison between the tomographic approach and a recent method elaborated by Wu, Poulsen and Molmer shows the better adequacy of the former method with respect to the latter one.
Scale-free relaxation of a wave packet in a quantum well with power-law tails
2013
We propose a setup for which a power-law decay is predicted to be observable for generic and realistic conditions. The system we study is very simple: A quantum wave packet initially prepared in a potential well with (i) tails asymptotically decaying like ~ x^{-2} and (ii) an eigenvalues spectrum that shows a continuous part attached to the ground or equilibrium state. We analytically derive the asymptotic decay law from the spectral properties for generic, confined initial states. Our findings are supported by realistic numerical simulations for state-of-the-art expansion experiments with cold atoms.
Single-Dish Radio Polarimetry in the F-GAMMA Program with the Effelsberg 100-m Radio Telescope
2013
Studying the variability of polarized AGN jet emission in the radio band is crucial for understanding the dynamics of moving shocks as well as the structure of the underlying magnetic field. The 100-m Effelsberg Telescope is a high-quality instrument for studying the long-term variability of both total and polarized intensity as well as the electric-vector position angle. Since 2007, the F-GAMMA program has been monitoring the linear polarized emission of roughly 60 blazars at 11 frequencies between 2.7 and 43 GHz. Here, we describe the calibration of the polarimetric data at 5 and 10 GHz and the resulting F-GAMMA full-Stokes light curves for the exemplary case of the radio galaxy 3C 111.
Monte Carlo evaluation of a CZT 3D spectrometer suitable for a Hard X- and soft-γ rays polarimetry balloon borne experiment
2015
Today, the measurement of the polarization status of cosmic sources high-energy' emission, is recognized as a key observational parameter to understand the active production mechanism and its geometry. Therefore, a mandatory requirement for new instrumentations operating in this energ.-y range will be to provide high sensitivity for polarimetric measurements. In this framework, we have presented the concept of a small high-performance imaging spectrometer optimized for polarimetry between 100 and 600 keV suitable for a stratospheric balloon-borne payload and as a pathfinder for a future satellite mission. The detector with 3D spatial resolution is based on a CZT spectrometer in a highly seg…
Hot electron noise in n-type GaAs in crossed electric and magnetic fields
2006
A Monte Carlo analysis of hot electron transport properties of bulk \textit{n}-type GaAs in crossed electric and magnetic fields is presented. %Magnetic field strengths allowing negligible quantum effects in the electron dynamics during free flights are considered. Effects due to the nonparabolicity of bands are properly taken into account by means of a local parabolic approximation. Stochastic properties of electron transport are analyzed by computing the velocity auto-correlation function and the spectral density of fluctuations. It is shown how the presence of the magnetic field is able to deeply modify electron noise up to high electric field strengths. The resulting features of the vel…