115,510 research outputs found
Interferometry from Space: A Great Dream
During some thirty years, 1980-2010, technical studies of optical
interferometry from instruments in space were pursued as promising for higher
spatial resolution and for higher astrometric accuracy. Nulling interferometry
was studied for both high spatial resolution and high contrast. These studies
were great dreams deserving further historical attention. ESA's interest in
interferometry began in the early 1980s. The studies of optical interferometry
for the global astrometry mission GAIA began in 1993 and ended in 1998 when
interferometry was dropped as unsuited for the purpose, and the Gaia mission to
be launched in 2013 is not based on interferometry. \c{opyright} Anita
Publications. All rights reserved.Comment: 12 pages, 7 figures. In: Asian Journal of Physics Vol. 23, Nos 1 & 2
(2014), Special Issue on History of Physics & Astronomy, Guest Editor:
Virginia Trimbl
Landau-Zener-Stuckelberg interferometry
A transition between energy levels at an avoided crossing is known as a
Landau-Zener transition. When a two-level system (TLS) is subject to periodic
driving with sufficiently large amplitude, a sequence of transitions occurs.
The phase accumulated between transitions (commonly known as the Stuckelberg
phase) may result in constructive or destructive interference. Accordingly, the
physical observables of the system exhibit periodic dependence on the various
system parameters. This phenomenon is often referred to as
Landau-Zener-Stuckelberg (LZS) interferometry. Phenomena related to LZS
interferometry occur in a variety of physical systems. In particular, recent
experiments on LZS interferometry in superconducting TLSs (qubits) have
demonstrated the potential for using this kind of interferometry as an
effective tool for obtaining the parameters characterizing the TLS as well as
its interaction with the control fields and with the environment. Furthermore,
strong driving could allow for fast and reliable control of the quantum system.
Here we review recent experimental results on LZS interferometry, and we
present related theory.Comment: 34 single-column pages, 11 figure
Modern optical astronomy: technology and impact of interferometry
The present `state of the art' and the path to future progress in high
spatial resolution imaging interferometry is reviewed. The review begins with a
treatment of the fundamentals of stellar optical interferometry, the origin,
properties, optical effects of turbulence in the Earth's atmosphere, the
passive methods that are applied on a single telescope to overcome atmospheric
image degradation such as speckle interferometry, and various other techniques.
These topics include differential speckle interferometry, speckle spectroscopy
and polarimetry, phase diversity, wavefront shearing interferometry,
phase-closure methods, dark speckle imaging, as well as the limitations imposed
by the detectors on the performance of speckle imaging. A brief account is
given of the technological innovation of adaptive-optics (AO) to compensate
such atmospheric effects on the image in real time. A major advancement
involves the transition from single-aperture to the dilute-aperture
interferometry using multiple telescopes. Therefore, the review deals with
recent developments involving ground-based, and space-based optical arrays.
Emphasis is placed on the problems specific to delay-lines, beam recombination,
polarization, dispersion, fringe-tracking, bootstrapping, coherencing and
cophasing, and recovery of the visibility functions. The role of AO in
enhancing visibilities is also discussed. The applications of interferometry,
such as imaging, astrometry, and nulling are described. The mathematical
intricacies of the various `post-detection' image-processing techniques are
examined critically. The review concludes with a discussion of the
astrophysical importance and the perspectives of interferometry.Comment: 65 pages LaTeX file including 23 figures. Reviews of Modern Physics,
2002, to appear in April issu
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