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The electric dipole moment of the ground state of cesium, d$\sb{\rm Cs}$, is measured. This result is related to the electric dipole moment of the electron in a straightforward way using the results of atomic theory calculations found in the literature. The resulting limit of the electric dipole moment of the electron represents a stringent test of time reversal invariance. Cesium vapor is studied at zero magnetic field in glass cells which also contain 250 torr of nitrogen. The ground state of cesium is optically pumped by a laser beam and the atomic orientation undergoes the electrical analog of Larmor precession due to an applied electric field. The precession is detected by comparing the transmission rates of left and right circularly polarized light for a second laser beam which is orthogonal to both the initial laser beam and the applied electric field. The Hamiltonians H = $\vec\mu\cdot\vec B$ and H = $\vec d\cdot\vec E$ are interchangeable allowing calibration of the apparatus using an applied magnetic field. During data acquisition all three components of the effective magnetic field are reduced below 100 nG. Comparing signals from two cells with opposite electric fields eliminates signals due to drifts in the homogeneous magnetic field. Comparing the signals from four cells, two with electric fields and two without, reduces noise due to fluctuating magnetic fields to about 150 pG in 20 seconds of integration (a single data point.) The precession frequency is determined with a statistical precision of 0.5 $\mu$Hz in a two day data collection run. A set of 13 data runs, 9 in the two cell configuration and 4 in the four cell configuration, is used to place upper limits d$\sb{\rm Cs}$ $<$ 1.1 $\times$ 10$\sp{-24}$e-cm, d$\sb{\rm e}$ $<$ 9.3 $\times$ 10$\sp{-27}$e-cm and a limit on T-violating electron-nucleon scaler interactions of C$\sb{\rm S}$ $<$ 10$\sp{-5}\rm G\sb{\rm F}$. This limit represents an order of magnitude improvement over the previously limits on d$\sb{\rm Cs}$ and constrains theories attempting to explain the violation of CP invariance which is seen in the K meson system.

Doctor of Philosophy / Department of Physics / Brett D. DePaola / In recent years, advance in ultra fast lasers and related optical technology has enhanced the ability to control the interaction between light and matter. In this dissertation, we try to improve our understanding of the interaction of atomic and molecular ladder systems with short optical pulses. A train of pulses produced by shaping the spectral phase of a single pulse from an ultra fast laser allows us to control the step-wise excitation in rubidium (Rb) atoms. As a diagnostic method, we use magneto-optical trap recoil ion momentum spectroscopy (MOTRIMS) to prepare cold target atoms and to observe atomic ions as a result of the interaction. We have explored the interactions of a finite number of optical short pulses in a train with a three-level Rb atom ladder system. Each pulse in the train is separated by a constant time interval with a fixed pulse-to-pulse phase change. In these experiments, two dimensional (2D) landscape maps show the interaction by measuring population in the uppermost state of the ladder system as a function of pulse-to-pulse time interval and phase shift. The observed structures in the 2D landscape are due to constructive or destructive interference in the interaction. Furthermore, different numbers of pulses in the train are applied to the atomic Rb three level ladder system in order to measure the effect on the interaction. The sharpness of the interference structure is enhanced by increasing the number of pulses. This phenomenon is analogous to increasing the sharpness in an optical multi-slit experiment by increasing the number of slits.

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<p>Worldwide there are significant efforts to build networks that can distribute photonic entanglement, first with applications in communication, with a long-term vision of constructing fully connected quantum processing networks (QPN). We have constructed a network of atom-light interfaces, providing a scalable QPN platform by creating connected room-temperature qubit memories using dark-state polaritons (DSPs). Furthermore, we combined ideas from two leading elements of quantum information namely collective enhancement effects of atomic ensembles and Cavity-QED to create a unique network element that can add quantum processing abilities to this network. We built a dual connection node consisting of two moderate finesse Fabry-Perot cavities. The cavities are configured to form a cross-cavity layout and coupled to a cold atomic ensemble. The physical regime of interest is the non-limiting case between (i) low N with high cooperativity and (ii) free-space-high-N ensembles. Lastly, we have explored how to use light-matter interfaces to implement an analog simulator of relativistic quantum particles following Dirac and Jackiw-Rebbi model Hamiltonians. Combining this development with the cross-cavity node provides a pathway towards quantum simulation of more complex phenomena involving interacting many quantum relativistic particles.

<p> Bose-Einstein condensates (BECs) are a recent addition to the portfolio of quantum materials some of which have profound commercial and military applications e.g., superconductors, superfluids and light emitting diodes. BECs exist in the lowest motional modes of a trap and have the lowest temperatures achieved by mankind. With full control over the shape of the trap the experimentalist may explore an extremely diverse set of Hamiltonians which may be altered mid-experiment. These properties are particularly suited for realizing novel quantum systems.</p><p> This thesis explores interaction-driven domain formation and the subsequent domain coarsening for two immiscible BEC components. Because quantum coherences associated with interactions in BECs can be derived from low energy scattering theory we compare our experimental results to both a careful simulation (performed by Brandon Anderson) and an analytical prediction. This result very carefully explores the question of how a metastable system relaxes at the extreme limit of low temperature.</p><p> We also explore spin-orbit coupling (SOC) of a BEC which links the linear and discrete momentum transferable by two counterpropagating ''Raman'' lasers that resonantly couple the ground electronic states of our BECs. SOC is used similarly in condensed matter systems to describe coupling between charge carrier spin and crystal momentum and is a necessary component of the quantum spin Hall effect and topological insulators.</p><p> SOC links the linear and discrete momentum transferable by two counterpropagating ''Raman'' lasers and a subset of the ground electronic states of our BEC. The phases of an effective 2-spin component spin-orbit coupling (SOC) in a spin-1 BEC are described in Lin et al. (2011). We measure the phase transition between two phases of a spin-1 BEC with SOC which cannot be mimicked by a spin-1/2 system. The order parameter that describes transitions between these two phases is insensitive to magnetic field fluctuations.</p><p> I also describe a realistic implementation of Rashba SOC. This type of SOC is expected to exhibit novel many-body phases [Stanescu et al. 2008, Sedrakyan et al. 2012, Hu et al. 2011].</p>

<p> We provide estimates of both cross section and rate for the stimulated attachment of a second positron into the (1<i>s</i>² ¹<i>S^e</i>) state of the <i>H&macr; </i>⁺ ion using Ohmura and Ohmura&rsquo;s (1960 Phys. Rev. 118 154) effective range theory, Reiss&rsquo;s strong field approximation (1980 Phys. Rev. A 22, 1786), and the principle of detailed balancing. Our motivation for producing <i>H&macr;</i>⁺ ion include its potential to be used as an intermediate state in bringing antihydrogen to ultra-cold (sub-mK) temperatures required for a variety of studies, which include both spectroscopy and the probing of the gravitational interaction of the anti-atom. We show that both cross section and rate are increased with the use of a resonant laser field.</p><p>

<p> Searches for violations of discrete symmetries can be sensitive probes of physics beyond the Standard Model. Many models, such as supersymmetric theories, introduce new particles at higher masses that include new <i> CP</i>-violating phases which are thought to be of order unity. Such phases could generate measurable permanant electric dipole moments (EDMs) of particles. The ACME collaboration has measured the electron's EDM to be consistent with zero with an order of magnitude improvement in precision compared to the previous best precision (J. Baron et al., ACME collaboration, <i> Science</i> <b>343</b> (2014), 269-272) with a spin precession measurement performed in the <i>H</i> state of a beam of thorium monoxide (ThO). This limit constrains time-reversal violating physics for particles with masses well into the TeV scale. In this thesis I discuss the details of this measurement with an emphasis on the data analysis, search for systematic errors, and systematic error models that contributed to this result. I also discuss implemented and planned upgrades to the experimental apparatus intended to both improve the statistical sensitivity and reduce its susceptibility to systematic errors. At this time, the upgraded apparatus has been demonstrated to have a statistical sensitivity to the electron EDM that is more than a factor of 10x more precise than our previous measurement. </p><p>

Non-contact atomic force microscopy allows us to directly probe the interactions between atoms and molecules. When operated in UHV and at low temperatures, a host of experiments, uniquely possible with the technique, can be carried out. The AFM allows us to characterise the forces present on a surface, resolve the atomic structure of molecules, measure the force required to move an atom, and even directly measure molecular pair potentials. Generally speaking, it is the interaction between the outermost tip and surface atoms that we measure. Therefore, in each of these experiments, understanding, or controlling, the tip termination is essential. As NC-AFM experiments become increasingly sophisticated, the combination of experiment and simulation has become critical to understand, and guide the processes at play. In this thesis, I focus on semiconductor surfaces and investigate the role of tip structure in a variety of situations with both DFT simulations and NC-AFM experiments. The clean Si(100) surface consists of rows of dimers, which can be manipulated between two different states using an NC-AFM. In order to understand the manipulation process, detailed DFT and NEB simulations were conducted to examine the energy balance of ideal and defective surfaces, with or without the presence of an AFM tip. We show that an explanation can only be reached when we consider both the AFM tip and variations in the PES caused by surface defects. NC-AFM experiments were also conducted on Si(100):H. We find that on this surface we regularly cultivate chemically passivated, hydrogen-terminated, tip apices which lead to distinct inverted image contrasts in our AFM images. Following a thorough characterisation of the tip apex, we conduct preliminary experiments designed to investigate surface defect structures, and to chemically modify the tip termination. Detailed DFT simulations show that this type of tip engineering, however, critically depends on the larger tip structure, significantly complicating the chances of success. Additionally, we investigate the structure and stability of silicon tip apices using DFT. Even with relatively simple tip structures, we observe complex behaviours, such as tip-dependent dissipation and structural development. These processes provide interesting information regarding tip stability, and commonly observed experimental behaviour. We also model an experiment in which we functionalise the tip apex with a C60 molecule, revealing for the first time that submolecular resolution is possible in the attractive regime.

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