Single-mode acceleration of matter waves in circular waveguides

Ultracold gases in ring geometries hold promise for significant improvements of gyroscopic sensitivity. Recent experiments have realized atomic and molecular storage rings with radii in the centimeter range, sizes whose practical use in inertial sensors requires velocities significantly in excess of typical recoil velocities. We use a combination of analytical and numerical techniques to study the coherent acceleration of matter waves in circular waveguides, with particular emphasis on its impact on single-mode propagation. In the simplest case we find that single-mode propagation is best maintained by the application of time-dependent acceleration force with the temporal profile of a Blackmann pulse. We also assess the impact of classical noise on the acceleration process.

Implementering av felpredikteringoch frekvenshopp i ett 2,4 GHzradiosystem

Maxicap AB är ett företag som utvecklar och tillverkar elektronisk utrustning för bland annat olika mätuppgifter. Målet med detta examensjobb var att undersöka och implementera en stabil trådlös dataöverföringsmetod med den utrustning som Maxicap ville använda. Detta skulle åstadkommas/testas genom att sända temperatursensorvärden trådlöst med Nordic Semiconductor’ssändtagare (eng. transceiver) styrda av Atmel’s mikrokontrollers. Arbetet fokuserade på att få till denna stabila trådlösa överföring genom att implementera frekvenshoppning och datapaketskontroll på datatrafiken inom det fria 2,4 GHz ISM-bandet. All den C-kod som utvecklades i detta arbete är skriven för att vara lättanpassad till flera olika modeller av mikrokontrollers inom Atmel’s produktserie samt att kunna användas till andra liknande projekt. Koden är väldokumenterad med kommentarer vid varje funktionsblock som beskriver vad funktionerna gör och hur de skall användas. Arbetet resulterade i två fungerande prototyper. En enhet känner av temperaturen i luften och skickar sedan detta temperaturvärde trådlöst till enhet nummer två. Detta värde samt några inställningsvärden för mottagaren visas sedan på den enhetens display.

Photovoltaic Process Development and innovative Techniques

Photovoltaic processing is one of the processes that have significance in semiconductor process line. It is complicated due to the no. of elements involved that directly or indirectly affect the processing and final yield. So mathematically or empirically we can’t say assertively about the results specially related with diffusion, antireflective coating and impurity poisoning. Here I have experimented and collected data on the mono-crystal silicon wafers with varying properties and outputs. Then by using neural network with available experimental data output required can be estimated which is further tested by the test data for authenticity. One can say that it’s a kind of process simulation with varying input of raw wafers to get desired yield of photovoltaic mono-crystal cells.

Anomalous spin-related quantum phase in mesoscopic hole rings

We have obtained numerically exact results for the spin-related geometric quantum phases that arise in p-type semiconductor ring structures. The interplay between gate-controllable (Rashba) spin splitting and quantum-confinement-induced mixing between hole-spin states causes a much higher sensitivity of magnetoconductance oscillations to external parameters than previously expected. Our results imply a much-enhanced functionality of hole-ring spin-interference devices and shed new light on recent experimental findings.

Thomas-Fermi ground state of dipolar fermions in a circular storage ring

Recent developments in the field of ultracold gases has led to the production of degenerate samples of polar molecules. These have large static electric-dipole moments, which in turn causes the molecules to interact strongly. We investigate the interaction of polar particles in waveguide geometries subject to an applied polarizing field. For circular waveguides, tilting the direction of the polarizing field creates a periodic inhomogeneity of the interparticle interaction. We explore the consequences of geometry and interaction for stability of the ground state within the Thomas-Fermi model. Certain combinations of tilt angles and interaction strengths are found to preclude the existence of a stable Thomas-Fermi ground state. The system is shown to exhibit different behavior for quasi-one-dimensional and three-dimensional trapping geometries.

Sagnac rotational phase shifts in a mesoscopic electron interferometer with spin-orbit interactions

The Sagnac effect is an important phase coherent effect in optical and atom interferometers where rotations of the interferometer with respect to an inertial reference frame result in a shift in the interference pattern proportional to the rotation rate. Here, we analyze the Sagnac effect in a mesoscopic semiconductor electron interferometer. We include in our analysis the Rashba spin-orbit interactions in the ring. Our results indicate that spin-orbit interactions increase the rotation-induced phase shift. We discuss the potential experimental observability of the Sagnac phase shift in such mesoscopic systems.