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

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