53,216 research outputs found
Time- and frequency-domain polariton interference
We present experimental observations of interference between an atomic spin
coherence and an optical field in a {\Lambda}-type gradient echo memory. The
interference is mediated by a strong classical field that couples a weak probe
field to the atomic coherence through a resonant Raman transition. Interference
can be observed between a prepared spin coherence and another propagating
optical field, or between multiple {\Lambda} transitions driving a single spin
coherence. In principle, the interference in each scheme can yield a near unity
visibility.Comment: 11 pages, 5 figure
High efficiency coherent optical memory with warm rubidium vapour
By harnessing aspects of quantum mechanics, communication and information
processing could be radically transformed. Promising forms of quantum
information technology include optical quantum cryptographic systems and
computing using photons for quantum logic operations. As with current
information processing systems, some form of memory will be required. Quantum
repeaters, which are required for long distance quantum key distribution,
require optical memory as do deterministic logic gates for optical quantum
computing. In this paper we present results from a coherent optical memory
based on warm rubidium vapour and show 87% efficient recall of light pulses,
the highest efficiency measured to date for any coherent optical memory. We
also show storage recall of up to 20 pulses from our system. These results show
that simple warm atomic vapour systems have clear potential as a platform for
quantum memory
Storage and Manipulation of Light Using a Raman Gradient Echo Process
The Gradient Echo Memory (GEM) scheme has potential to be a suitable protocol
for storage and retrieval of optical quantum information. In this paper, we
review the properties of the -GEM method that stores information in
the ground states of three-level atomic ensembles via Raman coupling. The
scheme is versatile in that it can store and re-sequence multiple pulses of
light. To date, this scheme has been implemented using warm rubidium gas cells.
There are different phenomena that can influence the performance of these
atomic systems. We investigate the impact of atomic motion and four-wave mixing
and present experiments that show how parasitic four-wave mixing can be
mitigated. We also use the memory to demonstrate preservation of pulse shape
and the backward retrieval of pulses.Comment: 26 pages, 13 figure
Extended Scaling for the high dimension and square lattice Ising Ferromagnets
In the high dimension (mean field) limit the susceptibility and the second
moment correlation length of the Ising ferromagnet depend on temperature as
chi(T)=tau^{-1} and xi(T)=T^{-1/2}tau^{-1/2} exactly over the entire
temperature range above the critical temperature T_c, with the scaling variable
tau=(T-T_c)/T. For finite dimension ferromagnets temperature dependent
effective exponents can be defined over all T using the same expressions. For
the canonical two dimensional square lattice Ising ferromagnet it is shown that
compact "extended scaling" expressions analogous to the high dimensional limit
forms give accurate approximations to the true temperature dependencies, again
over the entire temperature range from T_c to infinity. Within this approach
there is no cross-over temperature in finite dimensions above which
mean-field-like behavior sets in.Comment: 6 pages, 6 figure
Dissecting financial markets: Sectors and states
By analyzing a large data set of daily returns with data clustering
technique, we identify economic sectors as clusters of assets with a similar
economic dynamics. The sector size distribution follows Zipf's law. Secondly,
we find that patterns of daily market-wide economic activity cluster into
classes that can be identified with market states. The distribution of
frequencies of market states shows scale-free properties and the memory of the
market state process extends to long times ( days). Assets in the same
sector behave similarly across states. We characterize market efficiency by
analyzing market's predictability and find that indeed the market is close to
being efficient. We find evidence of the existence of a dynamic pattern after
market's crashes.Comment: 6 pages 4 figures. Additional information available at
http://www.sissa.it/dataclustering/fin
Development of the Motivational Interviewing Supervision and Training Scale
The movement to use empirically supported treatments has increased the need for researchers and supervisors to evaluate therapists’ adherence to and the quality with which they implement those interventions. Few empirically supported approaches exist for providing these types of evaluations. This is also true for motivational interviewing, an empirically supported intervention important in the addictions field. This study describes the development and psychometric evaluation of the Motivational Interviewing Supervision and Training Scale (MISTS), a measure intended for use in training and supervising therapists implementing motivational interviewing. Satisfactory interrater reliability was found (generalizability coefficient p2 = .79), and evidence was found supporting the convergent and discriminant validity of the MISTS. Recommendations for refinement of the measure and future research are discussed
X,Y,Z-Waves: Extended Structures in Nonlinear Lattices
Motivated by recent experimental and theoretical results on optical X-waves,
we propose a new type of waveforms in 2D and 3D discrete media -- multi-legged
extended nonlinear structures (ENS), built as arrays of lattice solitons (tiles
or stones, in the 2D and 3D cases, respectively). First, we study the stability
of the tiles and stones analytically, and then extend them numerically to
complete ENS forms for both 2D and 3D lattices. The predicted patterns are
relevant to a variety of physical settings, such as Bose-Einstein condensates
in deep optical lattices, lattices built of microresonators, photorefractive
crystals with optically induced lattices (in the 2D case) and others.Comment: 4 pages, 4 figure
Silicon dendritic web material
The development of a low cost and reliable contact system for solar cells and the fabrication of several solar cell modules using ultrasonic bonding for the interconnection of cells and ethylene vinyl acetate as the potting material for module encapsulation are examined. The cells in the modules were made from dendritic web silicon. To reduce cost, the electroplated layer of silver was replaced with an electroplated layer of copper. The modules that were fabricated used the evaporated Ti, Pd, Ag and electroplated Cu (TiPdAg/Cu) system. Adherence of Ni to Si is improved if a nickel silicide can be formed by heat treatment. The effectiveness of Ni as a diffusion barrier to Cu and the ease with which nickel silicide is formed is discussed. The fabrication of three modules using dendritic web silicon and employing ultrasonic bonding for interconnecting calls and ethylene vinyl acetate as the potting material is examined
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