3,177 research outputs found
A dynamic scheme for generating number squeezing in Bose-Einstein condensates through nonlinear interactions
We develop a scheme to generate number squeezing in a Bose-Einstein
condensate by utilizing interference between two hyperfine levels and nonlinear
atomic interactions. We describe the scheme using a multimode quantum field
model and find agreement with a simple analytic model in certain regimes. We
demonstrate that the scheme gives strong squeezing for realistic choices of
parameters and atomic species. The number squeezing can result in noise well
below the quantum limit, even if the initial noise on the system is classical
and much greater than that of a poisson distribution.Comment: 4 pages, 3 figure
Inverted GUI Development for IoT with Applications in E-Health
In the context of Internet of Things (IoT), the research of this dissertation is concerned with the development of applications for end-user devices, i.e. devices through which the end-user directly interacts with systems. The complexity of such applications is partly due to network intricacies, and partly because GUI (Graphical User Interface) development is generally complicated and time consuming. We employ a middleware framework called PalCom to manage the former, and focus our research on the problems of the latter, by expanding the scope of PalCom to also enable GUI development. In particular, the research goal is a more efficient GUI development approach that does not require program code to be written.To enable end-users with little or no programming experience to participate in the GUI development process, we eliminate the need for programming by introducing a new development approach. We view this approach as “inverted” in that the development focus is on presenting functionality from an application model as graphical components in a GUI, rather than on retroactively attaching functionality to manually added graphical components. The inverted GUI development approach is supported in two steps. First, we design a language for describing GUIs, and implement interpreters that communicate with remotely hosted application models and render GUI descriptions as fully functional GUIs. Second, we implement a graphical editor for developing GUIs in order to make the language more accessible.The presented solution is evaluated by its application in a number of research projects in the domain of e-health. From the GUIs developed in those projects, we conclude that the GUI language is practically viable for building full-blown, professional grade GUIs. Furthermore, the presented graphical editor is evaluated by direct comparison to a market leading product in a controlled experiment. From this, we conclude that the editor is accessible to new users, and that it can be more efficient to use than the commercial alternative
Pulse retrieval and soliton formation in a non-standard scheme for dynamic electromagnetically induced transparency
We examine in detail an alternative method of retrieving the information
written into an atomic ensemble of three-level atoms using electromagnetically
induced transparency. We find that the behavior of the retrieved pulse is
strongly influenced by the relative collective atom-light coupling strengths of
the two relevant transitions. When the collective atom-light coupling strength
for the retrieval beam is the stronger of the two transitions, regeneration of
the stored pulse is possible. Otherwise, we show the retrieval process can lead
to creation of soliton-like pulses.Comment: 11 figure
End-User Composition of Graphical User Interfaces for PalCom Systems
AbstractIn ubiquitous computing, end-user composition allows users to combine multiple single-purpose devices into new, interesting constellations. In PalCom – a ubiquitous middleware – this is achieved without the need to write program code. In this paper we present a solution that in the same way allows users to create Graphical User Interfaces (GUIs) for such systems without coding. The approach is to focus on presenting functionality in a GUI rather than attaching functionality to manually added components. We see this as an inverted way of working with GUI development. The solution was realized in the form of a graphical editor for a PalCom specific User Interface Description Language. The tool produces platform independent GUI descriptions that can be interpreted on any platform. When compared to another common tool, the presented editor exhibited roughly 10x shorter development times. The learning time for new users was also evaluated with positive outcome, and a scalability evaluation showed that the solution can be used to create professional grade GUIs
Low Energy Singlets in the Excitation Spectrum of the Spin Tetrahedra System Cu_2Te_2O_5Br_2
Low energy Raman scattering of the s=1/2 spin tetrahedra system
Cu_2Te_2O_5Br_2 is dominated by an excitation at 18 cm^{-1} corresponding to an
energy E_S=0.6\Delta, with \Delta the spin gap of the compound. For elevated
temperatures this mode shows a soft mode-like decrease in energy pointing to an
instability of the system. The isostructural reference system Cu_2Te_2O_5Cl_2
with a presumably larger inter-tetrahedra coupling does not show such a low
energy mode. Instead its excitation spectrum and thermodynamic properties are
compatible with long range Neel-ordering. We discuss the observed effects in
the context of quantum fluctuations and competing ground states.Comment: 5 pages, 2 figures, ISSP-Kashiwa 2001, Conference on Correlated
Electron
Developing Mobile Systems using PalCom -- A Data Collection Example
We developed a mobile system for collecting and communicating heart rate data in real-time using low cost, commonly available equipment. This system could be used to monitor patients with cardiac arrhythmia over long periods of time, hopefully increasing the chance of capturing and recording an actual fibrillation, which rarely is the case today. Such recordings are useful for physicians to find the right diagnosis. We have developed the system using the PalCom middleware and report on its usefulness for providing support for this kind of applications
Attosecond Control of Ionization Dynamics
Attosecond pulses can be used to initiate and control electron dynamics on a
sub-femtosecond time scale. The first step in this process occurs when an atom
absorbs an ultraviolet photon leading to the formation of an attosecond
electron wave packet (EWP). Until now, attosecond pulses have been used to
create free EWPs in the continuum, where they quickly disperse. In this paper
we use a train of attosecond pulses, synchronized to an infrared (IR) laser
field, to create a series of EWPs that are below the ionization threshold in
helium. We show that the ionization probability then becomes a function of the
delay between the IR and attosecond fields. Calculations that reproduce the
experimental results demonstrate that this ionization control results from
interference between transiently bound EWPs created by different pulses in the
train. In this way, we are able to observe, for the first time, wave packet
interference in a strongly driven atomic system.Comment: 8 pages, 4 figure
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