11,006 research outputs found
Steady-state entanglement in a double-well Bose-Einstein condensate through coupling to a superconducting resonator
We consider a two-component Bose-Einstein condensate in a double-well
potential, where the atoms are magnetically coupled to a single-mode of the
microwave field inside a superconducting resonator. We find that the system has
the different dark-state subspaces in the strong- and weak-tunneling regimes,
respectively. In the limit of weak tunnel coupling, steady-state entanglement
between the two spatially separated condensates can be generated by evolving to
a mixture of dark states via the dissipation of the photon field. We show that
the entanglement can be faithfully indicated by an entanglement witness.
Long-lived entangled states are useful for quantum information processing with
atom-chip devices.Comment: 9 pages, 7 figures, minor revisio
A VLSI design for a systolic Viterbi decoder
A systolic Viterbi decoder for convolutional codes is developed. This decoder uses the trace-back method to reduce the amount of data needed to be stored in registers. It is shown that this new algorithm requires a smaller chip size and achieves a faster decoding time than other existing methods
Coherent control of atomic spin currents in a double well
We propose an experimental feasible method for controlling the atomic
currents of a two-component Bose-Einstein condensate in a double well by
applying an external field to the atoms in one of the potential wells. We study
the ground-state properties of the system and show that the directions of spin
currents and net-particle tunneling can be manipulated by adiabatically varying
the coupling strength between the atoms and the field. This system can be used
for studying spin and tunneling phenomena across a wide range of interaction
parameters. In addition, spin-squeezed states can be generated. It is useful
for quantum information processing and quantum metrology.Comment: 6 pages, 7 figures, minor revisio
GEMINI: A Generic Multi-Modal Natural Interface Framework for Videogames
In recent years videogame companies have recognized the role of player
engagement as a major factor in user experience and enjoyment. This encouraged
a greater investment in new types of game controllers such as the WiiMote, Rock
Band instruments and the Kinect. However, the native software of these
controllers was not originally designed to be used in other game applications.
This work addresses this issue by building a middleware framework, which maps
body poses or voice commands to actions in any game. This not only warrants a
more natural and customized user-experience but it also defines an
interoperable virtual controller. In this version of the framework, body poses
and voice commands are respectively recognized through the Kinect's built-in
cameras and microphones. The acquired data is then translated into the native
interaction scheme in real time using a lightweight method based on spatial
restrictions. The system is also prepared to use Nintendo's Wiimote as an
auxiliary and unobtrusive gamepad for physically or verbally impractical
commands. System validation was performed by analyzing the performance of
certain tasks and examining user reports. Both confirmed this approach as a
practical and alluring alternative to the game's native interaction scheme. In
sum, this framework provides a game-controlling tool that is totally
customizable and very flexible, thus expanding the market of game consumers.Comment: WorldCIST'13 Internacional Conferenc
Xwnt-5A: a maternal Wnt that affects morphogenetic movements after overexpression in embryos of Xenopus laevis
To contribute to an understanding of the roles and mechanisms of action of Wnts in early vertebrate development, we have characterized the normal expression of Xenopus laevis Wnt-5A, and investigated the consequences of misexpression of this putative signalling factor. Xwnt-5A transcripts are expressed throughout development, and are enriched in both the anterior and posterior regions of embryos at late stages of development, where they are found primarily in ectoderm, with lower levels of expression in mesoderm. Overexpression of Xwnt-5A in Xenopus embryos leads to complex malformations distinct from those achieved by ectopic expression of Xwnts ā1, ā3A, or ā8. This phenotype is unlikely to result from Xwnt-5A acting as an inducing agent, as overexpression of Xwnt-5A does not rescue dorsal structures in UV-irradiated embryos, does not induce mesoderm in blastula caps, and Xwnt-5A does not alter the endogenous patterns of expression of goosecoid, Xbra, or Xwnt-8. To pursue whether Xwnt-5A has the capacity to affect morphogenetic movements, we investigated whether overexpression of Xwnt-5A alters the normal elongation of blastula cap explants induced by activin. Intriguingly, Xwnt-5A blocks the elongation of blastula caps in response to activin, without blocking the differentiation of either dorsal or ventral mesoderm within these explants. The data are consistent with Xwnt-5A having the potential activity of modifying the morphogenetic movements of tissues
Two-photon interference with thermal light
The study of entangled states has greatly improved the basic understanding
about two-photon interferometry. Two-photon interference is not the
interference of two photons but the result of superposition among
indistinguishable two-photon amplitudes. The concept of two-photon amplitude,
however, has generally been restricted to the case of entangled photons. In
this letter we report an experimental study that may extend this concept to the
general case of independent photons. The experiment also shows interesting
practical applications regarding the possibility of obtaining high resolution
interference patterns with thermal sources.Comment: Added reference 1
Object-Oriented Bayesian Networks (OOBN) for Aviation Accident Modeling and Technology Portfolio Impact Assessment
The concern for reducing aviation safety risk is rising as the National Airspace System in the United States transforms to the Next Generation Air Transportation System (NextGen). The NASA Aviation Safety Program is committed to developing an effective aviation safety technology portfolio to meet the challenges of this transformation and to mitigate relevant safety risks. The paper focuses on the reasoning of selecting Object-Oriented Bayesian Networks (OOBN) as the technique and commercial software for the accident modeling and portfolio assessment. To illustrate the benefits of OOBN in a large and complex aviation accident model, the in-flight Loss-of-Control Accident Framework (LOCAF) constructed as an influence diagram is presented. An OOBN approach not only simplifies construction and maintenance of complex causal networks for the modelers, but also offers a well-organized hierarchical network that is easier for decision makers to exploit the model examining the effectiveness of risk mitigation strategies through technology insertions
Super-resolving multi-photon interferences with independent light sources
We propose to use multi-photon interferences from statistically independent
light sources in combination with linear optical detection techniques to
enhance the resolution in imaging. Experimental results with up to five
independent thermal light sources confirm this approach to improve the spatial
resolution. Since no involved quantum state preparation or detection is
required the experiment can be considered an extension of the Hanbury Brown and
Twiss experiment for spatial intensity correlations of order N>2
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