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

1. The effect of deviations from Beer's law on the precision of atomic absorption analysis has been examined from a theoretical point of view, and a function has been derived which makes it possible to evaluate quantitatively the effect of calibration curvature on the precision of analysis. The influence of incomplete sample volatilization on calibration curvature has been briefly investigated. 2. Possible error sources in atomic absorption spectrometry have been classified according to the "error function" (i.e., the dependence, upon transmittance T, of the uncertainty dT in a given transmittance measurement) with which they are associated. The magnitude of the contribution from each component function to the overall error function has been evaluated quantitatively, and it has been shown that the major component in nearly every case examined is that associated with the dynamic nature of the flame. Concentration ranges for optimum precision are suggested. 3. The effect of varying instrumental parameters on precision has been investigated, and generalized conditions for best precision have been ascertained. 4. The effect of an initial solvent extraction step on the precision of atomic absorption has been investigated for the elements copper and lead. It is shown that solvent extraction may be used to improve both the analytical sensitivity and the precision of analysis when very low concentrations of metal are determined. 5. The precision of analytical methods involving atomic absorption spectrometry has been studied, and the standard deviations compared with those obtained for the analysis of similar samples by means of a variety of other methods of analysis, both instrumental and classical.

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.

The spark spectra of Tellurium have been photographed from the infrared to the ultraviolet (9040 Å to 340 Å) on a variety of spectrographs including a 3-metre normal, incidence vacuum spectrograph, a 2-metre grazing incidence vacuum spectrograph, a 21-ft, concave grating spectrograph, a Hilger Medium Quartz and a Hilger large automatic prism spectrograph. Two sources were used -1) a disruptive electrodeless discharge and 2) a condensed spark in helium, The "pole effect" exhibited by the spectral lines excited in the spark enabled us to assign each line to its appropriate ionic parent, either Te I, Te II, Te III, or Te IV. These excitation assignments were confirmed and extended by observations with the electrodeless discharge, which excited all the spectra including Te V and Te VI, by varying the tellurium pressure and the length of the external spark-gap. Out of 6000 lines appearing on our plates 3500 have never been observed earlier. The region 2200 Å - 1300 Å has been photographed systematically for the first time since Lacroute's work (1928). The whole of the observed spectral region has been photographed for the first time under uniform conditions of controlled excitation. These data have been used to confirm, revise and extend the analyses of Te III, Te IV, Te V and Te VI. In both Te III and Te IV the resonance lines have been indentified for the first time. The number of classified lines have been increased from 160 to 560 in Te III and from 25 to 230 in Te IV, while the number of the levels has been increased from 40 to 85 in Te III and from 14 to 56 in Te IV. The values of the ionization potentials have been revised to 29.04 Volts (Te III) and 37.41 Volts (Te IV). The hydrogenic levels in Te IV are fitted by a core polarization parameter A = 715 which involves a core dipole polarizability ∝= 41.1 x 10ˉ²⁸ cm³. The extensions in Te V and Te VI do not involve such basic additions. In Te V, the number of classified lines have been increased from 27 to 156 and in Te VI from 10 to 25. Twenty-four and five levels have been added to Te V and Te VI respectively. The revised values of the Ionization Potentials are 58.63 Volts and 70.90 Volts for Te V and Te VI respectively. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

This thesis investigates the possibility of constructing theories of composite particles of zero mass. Consideration is given primarily to the transformation properties of state vectors and operators used for the description of mass-less elementary particles under Lorentz transformation of the coordinate system. A method originally used by Wigner is developed more explicitly. The transformation properties of bilinear combinations of state functions and of operators are considered in some detail. It is found that the one example of a composite particle theory extant in the literature has incorrect transformation properties. No example of a correctly transforming theory is given. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A beam of polarized ³He⁺ ions has been produced using atomic beam method techniques. This method has the attraction of being capable of producing an ion beam with polarizations up to 100%. The polarization of ³He beams presently produced by optical pumping techniques is of the order of 5%. The apparatus is composed of three main sections, the atomic beam source consisting of a supersonic nozzle cooled to liquid helium temperatures to produce a low velocity atomic beam, the tapered hexapole magnet to spatially separate the particles in the two magnetic spin substates, and the electron bombardment ionizer to produce ³He⁺ ions from the neutral ³He atomic beam. The low velocity beam is required because the nuclear magnetic moment of ³He is of the order of 1000 times smaller than the electronic magnetic moment used to separate beams in conventional Stern-Gerlach magnets and to achieve a high ionization efficiency. The measured intensity of the beam produced by the atomic beam source cooled to liquid helium temperature was 1 x 10¹⁸ atoms/sr-sec, the most probable velocity was 310 m/sec, and the velocity full width at half maximum was 50 m/sec. The beam flux through the ionizer increases by a factor of 1.3 when the hexapole field is turned on, in good agreement with the theoretically expected increase. This increase corresponds to a polarization of 65% of the atomic beam. A 12nA³He⁺ ion beam was obtained corresponding to an ionization efficiency of approximately 0.15%. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The absolute transition probabilities between the 3p⁵4s and 3p⁵4p configurations of neutral argon have been measured in a three part experiment. In the first experiment, a technique of absorption spectroscopy was used to obtain relative transition probabilities for spectral lines with a common lower level. Secondly, relative transition probabilities were obtained for spectral lines with a common upper level by measuring the relative intensities of suitable pairs of lines in an emission experiment. In the third experiment, the relative values were converted to absolute transition probabilities by obtaining the lifetime of the P₁-S2 transition at ʎ7503Å. The experimental techniques used in this experiment were developed by Robinson (1966) and van Andel (1966). / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The spectra of tin have been photographed in the region between 350Å and 9000Å using as sources an electrodeless discharge and a condensed spark in helium. Exposure were taken by using a 3 meter normal incidence vacuum grating spectrograph and a Hilger E-478 large interchangeable quartz and glass prism spectrograph. Among thirty four hundred and four lines which were measured, two hundred and thirty five lines were classified in the spectra Sn I and Sn II on the basis of square arrays constructed by using the energy levels from Mrs. Sitterly's "Atomic Energy Levels", Volume III (1957). Five hundred and eleven lines are herein classified in the spectra Sn III, Sn IV and Sn V. / Science, Faculty of / Physics and Astronomy, Department of / Graduate