A Trapped Single Ion Inside a Bose-Einstein Condensate

In recent years, improved control of the motional and internal quantum states of ultracold neutral atoms and ions has opened intriguing possibilities for quantum simulation and quantum computation. Many-body effects have been explored with hundreds of thousands of quantum-degenerate neutral atoms and coherent light-matter interfaces have been built. Systems of single or a few trapped ions have been used to demonstrate universal quantum computing algorithms and to detect variations of fundamental constants in precision atomic clocks. Now in our experiment we investigate how the two systems can be advantageously combined. We immerse a single trapped Yb+ ion in a Bose-Einstein condensate of Rb atoms. Our hybrid setup consists of a linear RF-Paul trap which is overlapped with a magnetic trap and an optical dipole trap for the neutral atoms. A first synergetic effect is the sympathetic cooling of the trapped ions to very low temperatures through collisions with the ultracold neutral gas and thus without applying laser light to the ions. We observe the dynamics of this effect by measuring the mean ion energy after having an initially hot ion immersed into the condensate for various interaction times, while at the same time monitoring the effects of the collisions on the condensate. The observed ion cooling effect calls for further research into the possibility of using such hybrid systems for the continuous cooling of quantum computers. To this end a good understanding of the fundamental interaction processes between the ion and the neutrals is essential. We investigate the energy dependent elastic scattering properties by measuring neutral atom losses and temperature increase from an ultracold thermal cloud of Rb. By comparison with a Monte-Carlo simulation we gain a deeper understanding of how the different parameters affect the collisional effects. Additionally, we observe charge exchange reactions at the single particle level and measure the energy-independent reaction rate constants. The reaction products are identified by in-trap mass spectrometry, revealing the branching ratio between radiative and non-radiative charge exchange processes

Towards Measuring the Electron Electric Dipole Moment Using Trapped Molecular Ions

Permanent electric dipole moments have been the subject of experimental investigation for the past sixty years, as they entail the breaking of fundamental symmetries and provide a sensitive probe for physics beyond the Standard Model. This thesis describes an experiment aimed at measuring the electron electric dipole moment (eEDM) using trapped molecular ions. The 3Δ1 level of certain diatomic ions are desirable in eEDM searches due to their high polarizability, large eEDM enhancement factor, and relative insensitivity to magnetic fields. Ions allow for simple trapping and long interrogation times, but require a time-varying electric bias field in order to probe the eEDM. I will discuss the criteria for molecular ions in our experiment and our current candidates. A laser-ablation supersonic-expansion beam source has been developed to create and cool molecular ions. These ions have been loaded into a linear rf Paul trap and alternative photoionization methods for state-selective ion creation have been tested. Various experimental methods for performing the necessary spin resonance measurement are discussed. Sources of both decoherence and systematic errors have been identified and estimated. The experiment described in this thesis should be capable of a factor of 30 improvement on the current limit of the eEDM

Trapping and cooling of single molecular ions for time resolved experiments

In der vorliegenden Arbeit werden isolierte, einzeln ortsaufgelöste molekulare Ionen mit einer Femtosekundenspektroskopie auf der Basis von Einzelreaktionsereignissen untersucht. Für die zur simultanen Speicherung von atomaren und molekularen Ionen notwendige Radiofrequenzfalle wurde eine transportable Vakuumapparatur konzipiert und realisiert sowie die zugehörigen Lasersysteme aufgebaut und eingerichtet. Um die Ultrahochvakuumbedinungen bei 2e-10 mbar auch bei häufiger Molekülpräparation gewährleisten zu können, wurde ein modularer Aufbau gewählt, bei dem Präparations- und Expermentierbereich durch differentielle Pumpstrecken voneinander getrennt sind. Durch diese hindurch führt ein 48 cm langer Quadrupolionenleiter, in welchem Ionen zwischen den Kammern transferiert werden können. Entlang des Ionenleiters ermöglichen ringförmige Gleichspannungselektroden eine dreidimensionale Speicherung der Ionen. Im Rahmen dieser Arbeit wurde mit atomaren 24Mg+ und molekularen 24MgH+ Ionen gearbeitet. Erstere werden durch Photoionisation von Magnesiumatomen aus einem thermischen Strahl erzeugt und ihre Bewegungsenergie durch Laserkühlung soweit reduziert, dass sie in etwa 20 μm Abstand voneinander in einer kristallinen Struktur erstarren. Magnesiumhydridionen werden nach Einleiten von Wasserstoffgas in einer photochemischen Reaktion mit 24Mg+ generiert und – von verbleibenden atomaren Ionen sympathetisch gekühlt – auf Gitterplätze des Kristalls integriert. Bei der Laserkühlung von 24Mg+ ausgesendete Fluoreszenzphotonen ermöglichen die optische Detektion der Ionen mit derzeit bis zu 1 μm Ortsauflösung. Die nicht fluoreszierenden molekularen Ionen werden indirekt als vermeintlich unbesetzte Stellen der Kristallstruktur sichtbar. Neben der Demonstration des Erfolges unseres Fallenkonzepts sowie dessen Charakterisierung bildet der verlustfreie, kontrollierte Transport von atomaren und molekularen Ionen aus dem Präparations- in den Experimentierbereich, eine wichtige Errungenschaft, welche zu einem kontinuierlichen Nachladen von Ionen mit einer Rate von über 100 Hz ausgebaut werden kann. Diese Arbeit präsentiert eine Machbarkeitsstudie zur Kombination von Präzisionsmethoden zweier Forschungsgebiete. Dazu wurde die Fallenapparatur mit einem weiteren Vakuumsystem, in dem ultraviolette Femtosekundenpulse erzeugt werden können, über ein System von differenziellen Pumpstrecken verbunden. Als Resultat werden 5 fs zeitaufgelöste Pump-Probe Experimente vorgestellt, die die Oszillation eines Vibrationswellenpaketes von individuellen 24MgH+ Molekülionen zeigen. Dabei wird die Bewegung des Wellenpaketes auf die Dissoziationswahrscheinlichkeit in einem bestimmten Zerfallskanal abgebildet. Einzelne Reaktionsereignisse konnten eindeutig nachgewiesen und daraus das zeitabhängige Verhalten extrahiert werden. Diese Resultate untermauern das Potenzial der von uns angestrebten Kombination der exzellenten Kontrolle über externe und interne Freiheitsgrade gespeicherter Ionen mit der extremen Zeitauflösung von modernen Kurzpulslasern. Weitere Arbeiten können die Vorteile beider Gebiete nutzen um bisher unzugängliche Experimente zu realisieren. Die besonderen Eigenschaften der präsentierten Apparatur sollten es beispielsweise erlauben, einzelne isolierte molekulare Ionen mit hoher räumlicher Präzision und wohl kontrollierten Anfangsbedingungen für zukünftige Strukturuntersuchungen mittels derzeit entstehender, intensiver Kurzpuls-Röntgenquellen an freien Elektronenlasern bereitzustellen

Impedance-Based Analysis of the Cellular Response to Microparticles: Theory, Assay Development and Model Study

This thesis provides a model study on the information content of multimodal impedance-based assays to assess the impact of microscale particles on cell physiology of mammalian cells. In three main chapters, different approaches to this topic are presented and discussed: The first chapter focused on the simulation of several scenarios within cell-based assays. These simulations are all based on the so-called ECIS model, originally introduced by Giaever and Keese (1991), describing the impedance contribution of cell-covered gold-film electrodes. This theoretical part of the thesis should help to support the interpretation of impedance data. First, opening and closing of cell junctions (Rb) for different types of barrierforming cell layers were simulated and the accompanying changes in the complex impedance were extracted at various frequencies. The simulation data for some model epithelial and endothelial cell types showed that the relationship between resistance and barrier tightness may undergo inversion for frequencies above the cell-type specific threshold. Moreover, the influence of incomplete electrode coverage or inhomogeneity within the cell layer was studied systematically. For all experiments a good correlation between the simulated data and the experimental support was found. The aim of the second project was to establish a new opto-electrical assay to investigate the dye transfer via gap junctions into neighboring cells. The principle of this new assay was based on loading a selected cell population with Lucifer Yellow by in situ electroporation. The cell-type specific adjustment of the ac pulse parameters for a temporary permeabilization of the plasma membrane improved the incorporation of Lucifer Yellow into the cytoplasm without affecting NRK cell viability. The assay also required the optimization of the gold-film electrode layout which enabled the application of the ac pulses, the non-invasive impedance recordings before and after pulse application and the microscopic analysis of dye transfer from cells on the electrode into adjacent cells. The final electrode layout (8W4E-GJ) contained four “semi-elliptical” electrodes which were separated by a photopolymer-free gap to facilitate microscopic analysis without any interference from the red autofluorescence of the photopolymer. The development of an appropriate experimental protocol yielded on electroporation in Ca2+-free buffer and the application of two sequential ac pulses, as it was found to enhance the uptake efficiency into primary-loaded NRK cells. The opto-electrical assay was successfully applied to analyze the effect of the well-known gap junctional intercellular communication inhibitor 2-APB. The analysis of dye transfer via gap junctions was based on confocal fluorescence micrographs documenting dye transfer from the electrode into the photopolymer-free gap. The analysis was further improved by the application of the red-fluorescent TRITC dextran as co-electroporated reference dye, which was trapped in the cytoplasm of primary-loaded cells due to its molecular size. The image analysis of the position-dependent intensities of both dyes (TRITC dextran and Lucifer Yellow) allowed a quantification of gap junctional intercellular communication. The third chapter contains all sub-projects dealing with a multimodal and label-free analysis of the impact of micrometer-sized silica particles (Ø = 2 μm) on vitality, migration, proliferation and gap junctional intercellular communication of adherent NRK cells in vitro. A sequence of different impedimetric assays, all based on the well-established ECIS technique, was applied for the analysis of particle impact on cell physiology. Microscopic studies addressing the particle uptake revealed the presence of membrane-coated particles in the cytoplasm of NRK cells. Further evidence for particle uptake was gathered from ToFSIMS analysis that showed a densely-packed particle distribution around the cell nucleus in cells with intact plasma membranes. Time-resolved ECIS measurements revealed no acute cytotoxicity of silica particles as well as no influence on cell migration. Furthermore, the influence of silica particles on NRK proliferation was studied impedimetrically. No differences in the time-course of proliferation were found for particle-loaded or control cells. To study the influence of internalized particles on gap junctional intercellular communication the new optoelectrical assay was applied. Dye transfer to NRK cells in the periphery of the electrode was insignificantly different in absence and presence of silica particles. The results were supported by classical techniques, like FRAP analysis, scrape loading or parachute assay. Superior to other assays, the developed opto-electrical assay allowed for analysis of cell adhesion and cellular response to the presence of particle during an exposure time of 24 h prior to the dye transfer study. This enables the investigation of the impact of internalized particles on different cell-related parameters like viability, motility and gap junctional intercellular communication within one cell population

Ablation loading and qudit measurements with barium ions

Barium is one of the best ions for performing quantum information in a trapped-ion system. Its long-lived metastable D5/2 state allows for some interesting quantum operations, including the current best state preparation and measurement fidelity in qubits. This metastable state also opens up the possibility of implementing higher-dimensional qudits instead of qubits. However, installing a barium metal source in a vacuum chamber has shown to be somewhat of a challenge. Here, we present a loading technique which uses a barium chloride source instead, making it much easier to install. Laser ablation with a high-energy pulsed laser is used to generate neutral atoms, and a two-step photoionization technique is used to selectively load different isotopes of barium in our ion trap. The process of laser ablation and the plume of atoms it generates are characterized, informing us on how to best load ions. Loading is achieved, and selectivity of our method is demonstrated, giving us a reliable way to load 138Ba+ and 137Ba+ ions. The quadrupole transition into the metastable D5/2 state is investigated, with all of the individual transitions successfully found and characterized for 138Ba+ and 137Ba+. Coherent operations are performed on these transitions, allowing us to use them to define a 13-level qudit, on which we perform a state preparation and measurement experiment. The main error source in operations using this transition is identified to be magnetic field noise, and so we present attempts at mitigating this noise. An ac-line noise compensation method is used, which marginally improved the coherence time of the quadrupole transitions, and an additional method of using permanent magnets is proposed for future work. These efforts will help to make trapping barium more reliable, making it an even more attractive option for trapped ion systems. The state preparation and measurement results using the quadrupole transition to the long-lived metastable D5/2 state establish barium as an interesting platform for performing high-dimensional qudit quantum computing

Application of advanced surface patterning techniques to study cellular behavior

Surface manipulation for the fabrication of chemical or topographic micro- and nanopatterns, has been central to the evolution of in vitro biology research. A high variety of surface patterning methods have been implemented in a wide spectrum of applications, including fundamental cell biology studies, development of diagnostic tools, biosensors and drug delivery systems, as well as implant design. Surface engineering has increased our understanding of cell functions such as cell adhesion and cell-cell interaction mechanics, cell proliferation, cell spreading and migration. From a plethora of existing surface engineering techniques, we use standard microcontact printing methods followed by click chemistry to study the role of intercellular contacts in collective cancer cell migration. Cell dispersion from a confined area is fundamental in a number of biological processes, including cancer metastasis. To date, a quantitative understanding of the interplay of single cell motility, cell proliferation, and intercellular contacts remains elusive. In particular, the role of E- and N-Cadherin junctions, central components of intercellular contacts, is still controversial. Combining theoretical modeling with in vitro observations, we investigate the collective spreading behavior of colonies of human cancer cells (T24). The spreading of these colonies is driven by stochastic single-cell migration with frequent transient cell-cell contacts. We find that inhibition of E- and N-Cadherin junctions decreases colony spreading and average spreading velocities, without affecting the strength of correlations in spreading velocities of neighboring cells. Based on a biophysical simulation model for cell migration, we show that the behavioral changes upon disruption of these junctions can be explained by reduced repulsive excluded volume interactions between cells. This suggests that in cancer cell migration, cadherin-based intercellular contacts sharpen cell boundaries leading to repulsive rather than cohesive interactions between cells, thereby promoting efficient cell spreading during collective migration. Despite the remarkable progress in surface engineering technology and its applications, a combination of pattern properties such as stability, precision, specificity, high-throughput outcome and spatiotemporal control is highly desirable but challenging to achieve. Here, we introduce a versatile and high-throughput covalent photo-immobilization technique, comprising a light-dose dependent patterning step and a subsequent functionalization of the pattern via click chemistry. This two-step process is feasible on arbitrary surfaces and allows for generation of sustainable patterns and gradients. The method is validated in different biological systems by patterning adhesive ligands on cell repellent surfaces, thereby constraining the growth and migration of cells to the designated areas. We then implement a sequential photopatterning approach by adding a second switchable pattering step, allowing for spatiotemporal control over two distinct surface patterns. As a proof of concept, we reconstruct the dynamics of the tip/stalk cell switch during angiogenesis. Our results show that the spatiotemporal control provided by our “sequential photopatterning” system is essential for mimicking dynamic biological processes, and that our innovative approach has a great potential for further applications in cell science. In summary, this work introduces two novel and versatile paradigms of surface patterning for studying different aspects of cell behaviour in different cell types. The reliability of both setups is experimentally confirmed, providing new insight into the role of cell-cell contacts during collective cancer cell migration as well as the tip/stalk switch behaviour during angiogenesis

Implementation of Grover's Quantum Search Algorithm with Two Trapped Cadmium Ions.

Over the past decade, the field of trapped ion quantum computing has emerged as one of the leaders in quantum information processing due the level of manipulation available and the long coherence times possible in the system. As this thesis will demonstrate, all of the necessary building blocks for a quantum computer have been exhibited in ion traps and small scale quantum algorithms have been implemented. In this trapped ion system, quantum bits consist of the first order magnetic field insensitive ground state hyperfine levels of $^{111}$Cd$^+$. The qubits are manipulated via resonant and off-resonant coherent laser interactions. We experimentally realize Grover's quantum search algorithm over a 4 element database with n=2 trapped $^{111}$Cd$^+$ ion qubits. One of the four states is marked, and with a single query it is recovered, on average, with 60% probability. This exceeds the performance of any possible classical search, which can only succeed with 50% probability following a single query. The algorithm consists of two Molmer-Sorensen entangling gates, that utilize bichromatic stimulated Raman transitions to create a spin dependent force, paired with several single-qubit rotations and near-perfect qubit measurements. The spectral arrangement of the Raman beams is tailored to suppress phase noise accumulation between gates. This suppression is critical for reliably performing consecutive operations during the algorithm. Additionally, this thesis discusses the possibility of combining trapped ions with trapped neutral atoms for the purpose studying ultra-cold charge exchange interactions. It may be possible to conceal quantum information, initially prepared in an ionic qubit, inside a pure nuclear spin qubit for the purpose of transportation and storage. As a first step, we present the laser-cooling and confinement of Cd atoms in a magneto-optical trap, and characterize the loading process from the background Cd vapor. The trapping laser drives the $^{1}S_{0}$~$rightarrow$~$^{1}P_{1}$ transition at 229 nm in this two valence electron atom and also photoionizes atoms directly from the $^{1}P_{1}$ state. This photoionization dominates other loss mechanisms and allows a direct measurement of the photoionization cross section.Ph.D.PhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/57714/2/brickman_1.pd

Time-Frequency Distributions: Approaches for Incomplete Non-Stationary Signals

There are many sources of waveforms or signals existing around us. They can be natural phenomena such as sound, light and invisible like elec- tromagnetic fields, voltage, etc. Getting an insight into these waveforms helps explain the mysteries surrounding our world and the signal spec- tral analysis (i.e. the Fourier transform) is one of the most significant approaches to analyze a signal. Nevertheless, Fourier analysis cannot provide a time-dependent spectrum description for spectrum-varying signals-non-stationary signal. In these cases, time-frequency distribu- tions are employed instead of the traditional Fourier transform. There have been a variety of methods proposed to obtain the time-frequency representations (TFRs) such as the spectrogram or the Wigner-Ville dis- tribution. The time-frequency distributions (TFDs), indeed, offer us a better signal interpretation in a two-dimensional time-frequency plane, which the Fourier transform fails to give. Nevertheless, in the case of incomplete data, the time-frequency displays are obscured by artifacts, and become highly noisy. Therefore, signal time-frequency features are hardly extracted, and cannot be used for further data processing. In this thesis, we propose two methods to deal with compressed observations. The first one applies compressive sensing with a novel chirp dictionary. This method assumes any windowed signal can be approximated by a sum of chirps, and then performs sparse reconstruction from windowed data in the time domain. A few improvements in computational com- plexity are also included. In the second method, fixed kernel as well as adaptive optimal kernels are used. This work is also based on the as- sumption that any windowed signal can be approximately represented by a sum of chirps. Since any chirp ’s auto-terms only occupy a certain area in the ambiguity domain, the kernel can be designed in a way to remove the other regions where auto-terms do not reside. In this manner, not only cross-terms but also missing samples’ artifact are mitigated signifi- cantly. The two proposed approaches bring about a better performance in the time-frequency signature estimations of the signals, which are sim- ulated with both synthetic and real signals. Notice that in this thesis, we only consider the non-stationary signals with frequency changing slowly with time. It is because the signals with rapidly varying frequency are not sparse in time-frequency domain and then the compressive sensing techniques or sparse reconstructions could not be applied. Also, the data with random missing samples are obtained by randomly choosing the samples’ positions and replacing these samples with zeros

METHODS DEVELOPMENT AND APPLICATION OF TWO-DIMENSIONAL GEL ELECTROPHORESIS AND MASS SPECTROMETRY IN PROTEOMICS

The development of a highly sensitive ruthenium-based fluorescent staining solution isdescribed in this dissertation. The in-house synthesized ruthenium complex (RuMS)containing both sulfonated and non-sulfonated ligand has detection limit of 1 ng ofprotein that is better than colloidal coomassie, silver and ruthenium complex containingall sulfonated ligands (RuBPS). RuMS stain has 100-fold dynamic range and does notinterfere with subsequent mass spectral identification of proteins. The capability of inhousesynthesis of the staining solution makes it a viable cost-effective alternative to theexpensive commercially available fluorescent stain, Sypro Ruby. The low detection limit,broad linear dynamic range and compatibility with mass spectrometry, make thedevelopment of this stain a worthwhile pursuit. The staining solution was utilized insubsequent applications of two-dimensional gel electrophoresis (2-DE) technology.Proteomics methodology utilizing 2-DE and mass spectrometry was applied toinvestigate the effect of malathion on the proteome of human neuroblastoma cells.Results indicated that out of 122 proteins that were identified from the neuroblastomaproteome, sixteen proteins were down-regulated while five proteins were significantlyup-regulated after treatment with malathion. Significant down-regulation of calciummodulators like calmodulin and calgizarrin and other key chaperones makes themalathion-treated cells highly prone to oxidative stress. With increased awareness inpesticide related adverse effects, identification of altered proteins in malathion-treatedhuman neuroblastoma cells is a critical finding.Proteomics is a major area of research in the identification of biomarkers for diseases. Anovel immunoprecipitation method developed in this work allowed for successfulisolation and identification of albumin-interactome in cerebrospinal fluid (CSF) that isusually under-represented in standard CSF analysis using 2-DE. A key finding is thedifferential expression of various isoforms of proteins in CSF albumin-interactome fromAlzheimer\u27s disease (AD) subjects. The data implicate the acidic isoform ofprostaglandin D2 synthase (PGDS2) as a potential biomarker for AD. An understandingof the differential expression of these protein isoforms in AD will provide insight into theetiology of the disease and this can have far-reaching implication on drug developmentleading to the cure or even preventation of the disease

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance