A comprehensive computer package for the calculation and simulation of charged-particle dynamics in electromagnetic fields has been developed and tested. The program provides a user-friendly and flexible interface for visualizing particle dynamics using phase space diagrams, which are essential for complete understanding of a beam optics system. The program performs an accurate finite difference computation of a user-defined boundary value problem (in the form of a grid) followed by a high-order Runge-Kutta numerical integration of the equations of motion to evaluate the particle dynamics within the field. The program is unique in its combination of these flexible finite calculation techniques with the parallel processing of particle ensembles in order to display phase space diagrams. / After extensive testing, the program has been used to design a low emittance ion source and an ion beam deceleration system for high-efficiency ion collection. The program has also been used to analyze a radiofrequency quadrupole collisional focusing system using ion mobility concepts.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-05, Section: B, page: 3237. Adviser: Narayana R. Aluru. Includes bibliographical references (leaves 123-131) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--Lehigh University, 2008. / Adviser: John Huennekens.

The current frontier of our understanding of the physical universe is dominated by quantum phenomena. Uncovering the prospects and limitations of acquiring and processing information using quantum effects is an outstanding challenge in physical science. This thesis presents an analysis of several new model systems and applications for quantum information processing and metrology. First, we analyze quantum optomechanical systems exhibiting quantum phenomena in both optical and mechanical degrees of freedom. We investigate the strength of non-classical correlations in a model system of two optical and one mechanical mode. We propose and analyze experimental protocols that exploit these correlations for quantum computation. We then turn our attention to atom-cavity systems involving strong coupling of atoms with optical photons, and investigate the possibility of using them to store information robustly and as relay nodes. We present a scheme for a robust two-qubit quantum gate with inherent error-detection capabilities. We consider several remote entanglement protocols employing this robust gate, and we use these systems to study the performance of the gate in practical applications. Finally, we present a new protocol for running multiple, remote atomic clocks in quantum unison. We show that by creating a cascade of independent Greenberger-Horne-Zeilinger states distributed across the network, the scheme asymptotically reaches the Heisenberg limit, the fundamental limit of measurement accuracy. We propose an experimental realization of such a network consisting of neutral atom clocks, and analyze the practical performance of such a system. / Physics

Cold gases of atoms and molecules provide a system for the exploration of a diverse set of physical phenomena. For example, cold gasses of magnetically and electrically polar atoms and molecules are ideal systems for quantum simulation and quantum computation experiments, and cold gasses of large polar molecules allow for novel spectroscopic techniques. Buffer-gas cooling is a robust and widely applicable method for cooling atoms and molecules to temperatures of approximately 1 Kelvin. In this thesis, I present novel applications of buffer-gas cooling to obtaining gases of trapped, ultracold atoms and diatomic molecules, as well as the study of the cooling of large organic molecules. In the first experiment of this thesis, a buffer-gas beam source of atoms is used to directly load a magneto-optical trap. Due to the versatility of the buffer-gas beam source, we obtain trapped, sub-milliKelvin gases of four different lanthanide species using the same experimental apparatus. In the second experiment of this thesis, a buffer-gas beam is used as the initial stage of an experiment to directly laser cool and magneto-optically trap the diatomic molecule CaF. In the third experiment of this thesis, buffer-gas cooling is used to study the cooling of the conformational state of large organic molecules. We directly observe conformational relaxation of gas-phase 1,2-propanediol due to cold collisions with helium gas. Lastly, I present preliminary results on a variety of novel applications of buffer-gas cooling, such as mixture analysis, separation of chiral mixtures, the measurement of parity-violation in chiral molecules, and the cooling and spectroscopy of highly unstable reaction intermediates. / Chemical Physics

The study of quantum mechanics, together with the ability to coherently control and manipulate quantum systems in the lab has led to a myriad of discoveries and real world applications. In this thesis we present experiments demonstrating precise control of an individual long-lived spin qubit as well as sensing applications for biology and investigation of quantum many-body dynamics. Stable quantum bits, capable both of storing quantum information for macroscopic time scales and of integration inside small portable devices, are an essential building block for an array of potential applications. In the second chapter of this thesis we demonstrate high-fidelity control of a solid-state qubit, which preserves its polarization for several minutes and features coherence lifetimes exceeding 1 second at room temperature. Sensitive probing of temperature variations on nanometer scales is an outstanding challenge in many areas of modern science and technology. In chapter three we show how nitrogen vacancy centers in diamond can be used as a robust, high sensitivity temperature probe. We furthermore demonstrate biological compatibility by introducing nano-sized diamonds into living cells and measuring externally induced sub-cellular temperature gradients. Understanding the dynamics of interacting many-body quantum systems with on-site potential disorder has proven one of the biggest challenges in quantum physics to investigate both in theory and experiment. In chapter four we demonstrate how coherent control techniques can be utilized to probe the many-body dynamics of a strongly interacting NV spin ensemble. Specifically, we show how a long-range interacting dipolar spin system exhibits characteristically slow thermalization in the presence of tunable disorder. The presented works offer up many new areas to investigate, including complex quantum many-body effects of large, disordered spin systems, as well as applications of NV centers as bio-compatible nano-scale temperature probes. / Physics

Laser technology has steadily evolved over the last 50 years since its invention, and has generated a series of ramifications in experimental science. Particularly, lasers have enabled the creation of the shortest man-made event: a femtosecond pulse of electromagnetic radiation. Due to their unmatched spatial and temporal resolutions, femtosecond pulses have been used in a number of techniques to measure properties of individual molecules. One of these techniques is Coulomb Explosion Imaging (CEI), whose purpose is to retrieve the structure of individual molecules. Unlike frequency domain spectroscopy (which is ill-suited to characterize the structure of large molecules due to their complex spectra) and diffraction techniques (which only work if molecules can be locked into a crystallization pattern), CEI provides a direct measurement of the properties of individual molecules, instead of measuring a sample as a whole. This novel technique was first introduced to study molecular structure by colliding a beam of highly energetic ions onto a thin foil. The version of CEI used in this work uses a beam of neutral molecules and replaces the thin foil with femtosecond optical pulses. The introduction of the laser has brought with it the ability to conduct time-resolved measurements of molecular processes (breaking of molecular bonds, internuclear motion, for example) on a femtosecond time scale using pump-probe techniques in conjunction with CEI. Furthermore, CEI is presently the only technique that can discriminate single molecules based on their handedness. I have conducted a Laser Coulomb Explosion Imaging (LCEI) experiment using dicloromethane as a model polyatomic molecule. In order to perform LCEI, an intense femtosecond laser pulse is used to strip away electrons from a molecule and cause it to explode into smaller fragments. Imaging the molecule is done using data collected from its fragments. Thus, in practice LCEI can be seen as a technique comprising an experimental phase (Coulomb explosion) and an analytical phase (imaging). Dichloromethane was chosen for this study to prepare the techniques that are necessary for future experiments on chiral molecules. The experimental setup used for this instance of LCEI is the PATRICK instrument, a combination of high-end vacuum, electronics and laser equipment, which will also be described herein. The rest of this thesis will focus on the results obtained from the computational tools I developed for imaging the CEI data and obtaining physical properties about the exploded molecules. In doing so I have also obtained the first geometrical reconstructions of five atom molecules from CEI data, which will also be given in this study. Though LCEI is a general technique that can be exploited in a variety of different experiments, this particular project was built around the interest of imaging chiral molecules. Unlike mass, multipole moments, polarizabilities and other "conventional" physical properties of molecules, chirality arises solely from spatial symmetry considerations, making it more elusive. For example, in order to experimentally determine the properties of a molecule in the traditional manner, one proceeds by inferring molecular characteristics from general spectroscopic data pertaining to a sample of molecules. In this manner, molecules are ascribed properties based on statistical measurements done on a population. Although statistical methods are also used to measure the handedness of a sample of molecules, it is understood that these measurements yield information only about the sample, but not the individual molecules themselves. Indeed, chirality is not a property of a type of molecule, but of individual molecules, rendering LCEI very suitable to measure chirality. Accordingly, it is the ultimate goal of this thesis to set the stage for future experiments involving the measurement of the handedness of individual chiral molecules.

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