Cooling the motion of a trapped atom with a cavity field

We theoretically analyze the cooling dynamics of an atom which is tightly trapped inside a high-finesse optical resonator. Cooling is achieved by suitably tailored scattering processes, in which the atomic dipole transition either scatters a cavity photon into the electromagnetic field external to the resonator, or performs a stimulated emission into the cavity mode, which then dissipates via the cavity mirrors. We identify the parameter regimes in which the atom center-of-mass motion can be cooled into the ground state of the external trap. We predict, in particular, that for high cooperativities interference effects mediated by the atomic transition may lead to higher efficiencies. The dynamics is compared with the cooling dynamics of a trapped atom inside a resonator studied in [Phys. Rev. Lett. 95, 143001, (2005)] where the atom, instead of the cavity, is driven by a laser field

Anomalously Slow Cross Symmetry Phase Relaxation, Thermalized Non-Equilibrated Matter and Quantum Computing Beyond the Quantum Chaos Border

Thermalization in highly excited quantum many-body system does not necessarily mean a complete memory loss of the way the system was formed. This effect may pave a way for a quantum computing, with a large number of qubits $n\simeq 100$--1000, far beyond the quantum chaos border. One of the manifestations of such a thermalized non-equilibrated matter is revealed by a strong asymmetry around 90$^\circ$ c.m. of evaporating proton yield in the Bi($\gamma$,p) photonuclear reaction. The effect is described in terms of anomalously slow cross symmetry phase relaxation in highly excited quantum many-body systems with exponentially large Hilbert space dimensions. In the above reaction this phase relaxation is about eight orders of magnitude slower than energy relaxation (thermalization).Comment: Published in SIGMA (Symmetry, Integrability and Geometry: Methods and Applications) at http://www.emis.de/journals/SIGMA

Opacity of electromagnetically induced transparency for quantum fluctuations

We analyze the propagation of a pair of quantized fields inside a medium of three-level atoms in $\Lambda$ configuration. We calculate the stationary quadrature noise spectrum of the field after propagating through the medium, in the case where the probe field is in a squeezed state and the atoms show electromagnetically induced transparency (EIT). We find an oscillatory transfer of the initial quantum properties between the probe and pump fields which is most strongly pronounced when both fields have comparable Rabi frequencies. This implies that the quantum state measured after propagation can be completely different from the initial state, even though the mean values of the field are unaltered

Inelastic scattering of light by a cold trapped atom: Effects of the quantum center-of-mass motion

The light scattered by a cold trapped ion, which is in the stationary state of laser cooling, presents features due to the mechanical effects of atom-photon interaction. These features appear as additional peaks (sidebands) in the spectrum of resonance fluorescence. Among these sidebands the literature has discussed the Stokes and anti-Stokes components, namely the sidebands of the elastic peak. In this manuscript we show that the motion also gives rise to sidebands of the inelastic peaks. These are not always visible, but, as we show, can be measured in parameter regimes which are experimentally accessible.Comment: 10 pages, 4 figures, submitted to Phys. Rev.

Effect of phase relaxation on quantum superpositions in complex collisions

We study the effect of phase relaxation on coherent superpositions of rotating clockwise and anticlockwise wave packets in the regime of strongly overlapping resonances of the intermediate complex. Such highly excited deformed complexes may be created in binary collisions of heavy ions, molecules and atomic clusters. It is shown that phase relaxation leads to a reduction of the interference fringes, thus mimicking the effect of decoherence. This reduction is crucial for the determination of the phase--relaxation width from the data on the excitation function oscillations in heavy--ion collisions and bimolecular chemical reactions. The difference between the effects of phase relaxation and decoherence is discussed.Comment: Extended revised version; 9 pages and 3 colour ps figure

Упрощенная система учета и налогообложения

Объём работы – 76 с., иллюстраций – 2, таблиц – 12, формул – 2, источников – 52. Актуальность выбранной темы исследования заключается в уникальности КПКГ, как некоммерческих организаций, подлежащих упрощенной системе налогообложения, несмотря на наличие в них кредиторской деятельности. Объектом исследования является кредитно-потребительский кооператив граждан «Традиция». Предмет исследования – упрощенная система налогообложения КПКГ. Цель ВКР – исследование сущности и практики применения упрощенной системы налогообложения потребительских кредитных кооперативов граждан на примере КПКГ «Традиция».Volume of work - 76, illustration -. 2, tables - 12, formulas - 2, sources - 52. The relevance of the chosen research topic is unique CCCC as non-profit organizations are subject to a simplified system of taxation, despite the presence of accounts activity. The object of this study is to credit and consumer cooperative citizens "Tradition". Subject of research - the simplified taxation system CCCC. The purpose of the WRC - study the nature and practice of application of the simplified tax system consumer credit cooperatives of citizens the example of CCCC "Tradition"

Large-Eddy Simulation of inhomogeneous canopy flows using high resolution terrestrial laser scanning data

The effect of sub-tree forest heterogeneity in the flow past a clearing is investigated by means of large-eddy simulation (LES). For this purpose, a detailed representation of the canopy has been acquired by terrestrial laser scanning for a patch of approximately 190m length in the field site “Tharandter Wald”, near the city of Dresden, Germany. The scanning data are used to produce a high resolution plant area distribution (PAD) that is averaged over approximately one tree height (30m) along the transverse direction, in order to simplify the LES study. Despite the smoothing involved with this procedure, the resulting two-dimensional PAD maintains a rich vertical and horizontal structure. For the LES study, the PAD is embedded in a larger domain covered with an idealized, horizontally homogeneous canopy. Simulations are performed for neutral conditions and compared to a LES with homogeneous PAD and recent field measurements. The results reveal a considerable influence of small-scale plant distribution on the mean velocity field as well as on turbulence data. Particularly near the edges of the clearing, where canopy structure is highly variable, usage of a realistic PAD appears to be crucial for capturing the local flow structure. Inside the forest, local variations in plant density induce a complex pattern of upward and downward motions, which remain visible in the mean flow and make it difficult to identify the “adjustment zone” behind the windward edge of the clearing

Large-Eddy Simulation Study of the Effects on Flow of a Heterogeneous Forest at Sub-tree Resolution

Abstract The effect of three-dimensional plant heterogeneity on flow past a clearing is investigated by means of large-eddy simulation. A detailed representation of the canopy has been acquired by terrestrial laser scanning for a patch of approximately 328m length and 172m width at the field site “TharandterWald”, near the city of Dresden, Germany. The scanning data are used to produce a highly resolved, three-dimensional plant area distribution representing the actual canopy. Hence, the vegetation maintains a rich horizontal and vertical structure including the three-dimensional clearing. The scanned plant area density is embedded in a larger domain, which is filled with a heterogeneous forest generated by the virtual canopy generator of Bohrer et al. (Tellus B 59:566–576, 2007). Based on forest inventory maps and airborne laser scanning, the characteristics of the actual canopy are preserved. Furthermore, the topography is extracted from a digital terrain model with some modifications to accommodate for periodic boundary conditions. A large-eddy simulation is performed for neutral atmospheric conditions and compared to simulations of a two-dimensional plant area density and an one-year-long field experiment conducted at the corresponding field site. The results reveal a considerable influence of the plant heterogeneity on the mean velocity field as well as on the turbulent quantities. The three-dimensional environment, e.g., the oblique edges combined with horizontal and vertical variations in plant area density and the topography create a sustained vertical and cross-flow velocity. Downstream of the windward forest edge an enhanced gust zone develops, whose intensity and relative position are influenced by the local canopy density and, therefore, is not constant along the edge. These results lead us to the conclusion that the usage of a three-dimensional plant area distribution is essential for capturing the flow features inside the canopy and within the mixing layer above

3D-Vegetationsmodell aus Laserscannerdaten für forstmeteorologische Anwendungen am Beispiel des TurbEFA-Projektes

3D-Vegetationsmodelle sind in der Forstmeteorologie ein essentieller Bestandteil um Modellierungen durchzuführen und Messmethoden zu validieren. Inhomogenitäten, wie Änderungen der Bestandshöhe und Lichtungen in Waldbeständen, beeinflussen die Entstehung und die Struktur von turbulenten Windfeldern. Auch die numerische Simulation hochturbulenter Strömungen erfordert eine enorme Rechenleistung unter Verwendung von Vegetationsdaten. Daher ist die Anwendung von Vegetationsmodellen unterschiedlicher Art dringend notwendig. Während bisher die Verteilung der Biomasse von Untersuchungsgebieten über herkömmliche Methoden (Forstinventur, Abgriff aus Forstkarten) erfasst wurde, ist das Flugzeuglaserscanning (ALS) sowie das terrestrische Laserscanning (TLS) ein interessantes Werkzeug zur detaillierten Vegetationserfassung (Maas, 2010). Der Beitrag gibt einen Überblick über die Möglichkeiten der Generierung von Vegetationsmodellen aus verschiedenen Laserscannerdaten. Während Flugzeuglaserscanner große Gebiete aus der Luft erfassen können, sind die terrestrischen Laserscanner aufgrund der bodennahen Standpunkte auf kleinere Gebiete begrenzt. ALS- und TLS-Datensätze sind insofern komplementär, als Flugzeuglaserscannerdaten primär Kronenbereiche erfassen, während TLS-Aufnahmen hochaufgelöste Informationen über Baumstämme und den unteren Kronenbereich liefern. Eine vergleichsweise neue Messmethode im ALS ist das Full- Waveform Laserscanning, bei der das gesamte Intensitätssignal der reflektierten Energie aufgezeichnet und digitalisiert wird. Dadurch ist eine Volumenrekonstruktion der vertikalen Bestandsschicht möglich. Das Verfahren zeigt höhere Genauigkeiten hinsichtlich der Biomasseabschätzung im Vergleich zu dem herkömmlichen Flugzeuglaserscanning. Die unorganisierten 3D-Punktwolken, wie sie beim terrestrischen und Flugzeuglaserscanning entstehen, sind in der Regel für numerische Simulationen nicht handhabbar. Durch geeignete 3D-Datenstrukturen werden Gitterstrukturen auf Basis der Punktwolken aufgebaut und für numerische Simulationsprozesse nutzbar gemacht. Durch die Projektion der Full-Waveform Flugzeuglaserscannerdaten in diese Datenstruktur ergibt sich eine Voxelraumrepräsentation eines Waldbestandes. Hochaufgelöste TLS-Vegetationsscans ermöglichen eine detailliertere Parametrisierung der Pflanzenarchitektur. Über statistische und punktverteilungsbeschreibende Parameter aus den Punkten einer Gitterzelle können u.a. Informationen über Pflanzenflächendichte-Verteilungen (PAD) abgeleitet werden. Die standpunktweise Reflexionswahrscheinlichkeit pro Voxel wird mit Ray-Tracing Methoden bestimmt und repräsentiert den PAD (Queck et., 2012). Die Verwendung dieser Daten zielt auf eine genauere Modellierung der Strömungseffekte an Waldrandkanten, als natürliche Inhomogenität, ab, welche Forschungsschwerpunkt des interdisziplinären Projektes TurbEFA (Turbulent Exchange processes between Forested areas and the Atmosphere) ist