We demonstrate a resonance imaging protocol for optical lattices that enables robust preparation and single qubit addressing of atoms with sub-wavelength resolution in 1D. A 3D optical lattice consisting of three sets of independent 1D counter- propagating laser beams provides the trapping potential for the atoms. On this optical lattice platform, a long-period 1D superlattice is imposed by interfering two laser beams at a shallow angle centered at the atoms. This superlattice creates a position-dependent shift of the qubit transition frequency defined between two spin states in the ground manifold. Isolated 2D planes of atoms are prepared by flipping the resonant spins with a microwave pulse and removing the non-resonant spins by pushing them out of the lattice with a resonant laser beam. The periodic planes of atoms that are prepared can be imaged by applying another microwave pulse and detecting the fluorescence from the spins that flip back to the initial state, as a function of superlattice displacement between the preparation and read-out pulses. By employing these new techniques for sub-wavelength imaging, we tested the effectiveness of using composite pulses for addressing the trapped atoms in an optical lattice. Composite pulse techniques can be used to reduce the sensitivity of the addressing to small variations in the relative position and intensity of the lattices. This robustness is achieved by applying numerically generated composite pulses that have a constant atomic response within a target range of relative lattice positions and intensities. We designed a composite microwave pulse that flips the spin with near unit fidelity for all atoms that are positioned within a target spatial region, while conserving the spin of the atoms outside of that region. This cannot be accomplished with plain pulses due to off-resonant excitation. We also expanded the concept of this technique for robustly addressing spins even further to implement independent unitaries, or single qubit quantum gates, across several adjacent lattice sites. Finally, in order to quantitatively measure the fidelity of these robust composite pulses, we perform a randomized benchmarking procedure, which was first proposed by Knill.

We study a system of neutral atoms trapped in a three-dimensional optical lattice suitable for the encoding, initialization and manipulation of atomic qubits. The qubits are manipulated by applied electromagnetic fields interacting with dipole moments of the atoms via light shifts, Raman transitions, Zeeman shifts, and microwave transitions. Our lattice is formed by three orthogonal one-dimensional lattices, which have different frequencies so that interference terms average to zero. This geometry allows considerable freedom in designing the component one-dimensional lattices, so that they provide not only confinement but also independent control in each dimension. Our atomic qubits are initialized from a laser-cooled atomic sample by Raman sideband cooling in individual lattice potential wells. We have demonstrated accurate and robust one-qubit manipulation using resonant microwave fields. In practice such control operations are always subject to errors, in our case spatial inhomogeneities in the microwave Rabi frequency and the light shifted qubit transition frequency. Observation of qubit dynamics in near real time allows us to minimize these inhomogeneities, and therefore optimize qubit logic gates. For qubits in the lattice, we infer a fidelity of 0.990(3) for a single pi-pulse. We have also explored the use of NMR-type pulse techniques in order to further reduce the effect of errors and thus improve gate robustness in the atom/lattice system. Our schemes for two-qubit quantum logic operations are based on controlled collisional interactions. We have experimented with two schemes in order to probe these collisions. The first involves manipulation of the center-of-mass wavepackets of two qubits in a geometry corresponding to two partially overlapping Mach-Zender interferometers. Unfortunately, this scheme has proven extremely sensitive to phase errors, as the wavepackets are moved by the optical lattice. The other scheme starts with two qubits in spatially separated traps, and utilizes microwaves to drive one or both qubits into a third trap in-between the two qubits. Once the wavepackets overlap, the collisions create a large energy shift which can be probed spectroscopically.

In this thesis, we demonstrate the creation and characterization of multiparticle entangled states of neutral atoms with the help of a high finesse cavity. Our experimental setup consists of a fibre-based high finesse cavity above the surface of an atom chip. It allows us to prepare an ensemble of 87Rb atoms with well-defined atom number. The atoms are trapped in a single antinode of an intracavity standing wave dipole trap and are therefore all equally coupled to the cavity mode. We present a scheme based on a collective, quantum non-destructive (QND) measurement and conditional evolution to create symmetric entangled states and to analyze them at the single-particle level by directly measuring their Husimi Q function. We use this method to create and characterize W states of up to 41 atoms. From the tomography curve of the Q function, we reconstruct the symmetric part of the density matrix via different reconstruction techniques and obtain a fidelity of 0.42. Furthermore, we have devised an entanglement criterion which only relies on comparing two populations of the density matrix. We use it to infer the degree of multiparticle entanglement in our experimentally created states and find that the state with highest fidelity contains at least 13 entangled particles. In addition, we show preliminary results on experiments to count the atom number inside a cavity in the QND regime and to create entangled states via quantum Zeno dynamics.

xvi, 119 p. ; ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / This dissertation describes the development of an apparatus that can accommodate many atom-optics experiments, as well as an experimental demonstration of an optical one-way barrier for neutral atoms. The first part of this dissertation describes in detail the design and implementation of our apparatus. The experiment setup consists of optical systems, vacuum systems, imaging systems, and the related electronics. It is designed to be versatile enough for many cold-atom experiments, including the demonstration of an optical one-way barrier for neutral atoms, quantum measurement on the single-atom level, and the study of quantum chaos using Bose-Einstein condensates. The second part of this thesis presents the experimental study of an optical one-way barrier for neutral atoms. We demonstrated an asymmetric optical potential barrier for ultracold 87 Rb atoms. The atoms are confined in a far-detuned dipole trap consisting of a single focused Gaussian beam from a fiber laser. The optical one-way barrier consists of two focused laser beams oriented nearly normal to the dipole-trap axis and tuned near the 87 Rb D 2 transition. The first beam (main barrier beam) is tuned to work as either a potential well or barrier, depending on the state of the incident atoms. The second beam (repumping barrier beam) pumps the atoms to the barrier state on the reflecting side. We investigated the transmission and reflection dynamics of the atoms in the presence of the one-way barrier, and we verified its capability for increasing the phase-space density of a sample of neutral atoms using the one-way barrier. Our experiment is a realization of Maxwell's demon and has important implications for cooling atoms and molecules not susceptible to the standard laser-cooling techniques. / Adviser: Daniel A. Steck

The lunar space environment is shaped by the interaction between the Moon and the solar wind. In the present thesis, we investigate two aspects of this interaction, namely the interaction between solar wind protons and lunar crustal magnetic anomalies, and the interaction between solar wind protons and lunar regolith. We use particle sensors that were carried onboard the Chandrayaan-1 lunar orbiter to analyze solar wind protons that reflect from the Moon, including protons that capture an electron from the lunar regolith and reflect as energetic neutral atoms of hydrogen. We also employ computer simulations and use a hybrid plasma solver to expand on the results from the satellite measurements. The observations from Chandrayaan-1 reveal that the reflection of solar wind protons from magnetic anomalies is a common phenomenon on the Moon, occurring even at relatively small anomalies that have a lateral extent of less than 100 km. At the largest magnetic anomaly cluster (with a diameter of 1000 km), an average of ~10% of the incoming solar wind protons are reflected to space. Our computer simulations show that these reflected proton streams significantly modify the global lunar plasma environment. The reflected protons can enter the lunar wake and impact the lunar nightside surface. They can also reach far upstream of the Moon and disturb the solar wind flow. In the local environment at a 200 km-scale magnetic anomaly, our simulations show a heated and deflected plasma flow and the formation of regions with reduced or increased proton precipitation. We also observe solar wind protons reflected from the lunar regolith. These proton fluxes are generally lower than those from the magnetic anomalies. We find that the proton reflection efficiency from the regolith varies between ~0.01% and ~1%, in correlation with changes in the solar wind speed. We link this to a velocity dependent charge-exchange process occurring when the particles leave the lunar regolith. Further, we investigate how the properties of the reflected neutral hydrogen atoms depend on the solar wind temperature. We develop a model to describe this dependence, and use this model to study the plasma precipitation on the Moon when it is in the terrestrial magnetosheath. We then use the results from these and other studies, to model solar wind reflection from the surface of the planet Mercury. / Rymdmiljön runt månen formas av den växelverkan som sker mellan månen och solvinden. I den föreliggande avhandlingen undersöker vi två aspekter av denna växerverkan, nämligen växelverkan mellan solvindsprotoner och magnetiserade områden i månskorpan, och växelverkan mellan solvindsprotoner och månens ytdamm. Vi använder oss av partikelsensorer på månsatelliten Chandrayaan-1 för att analysera solvindsprotoner som reflekteras från månen, även de protoner som fångar upp en elektron från ytan och reflekteras som neutrala väteatomer. Vi använder oss också av datorsimuleringar för att bygga vidare på de uppmätta resultaten. Observationerna från Chandrayaan-1 visar att reflektion av solvindsprotoner från magnetiserade områden är ett vanligt förekommande fenomen på månen, som inträffar även vid magnetiseringar som är utbredda över mindre än 100 km. Vid det största magnetiserade området på månen (1000 km i diameter), reflekteras i genomsnitt ~10% av de infallande solvindsprotonerna. Våra datorsimuleringar visar att dessa protonflöden har globala effekter på månens plasmamiljö. De reflekterade protonerna kan nå månens nattsida. De kan också nå långt uppströms om månen och störa solvindsflödet. I den lokala plasmamiljön vid ett magnetiserat område av storleken 200 km visar våra simuleringar ett förändrat solvindsflöde, där det skapas områden som delvis skyddas från solvinden, likväl som områden som utsätts för mer solvind. Vi observerar även solvindsprotoner som reflekterats från ytdammet på månen. Dessa protonflöden är lägre än de från de magnetiska fälten. Reflektionen från ytan varierar mellan ~0.01% och 1% av solvindsflödet, i samband med förändringar i solvindshastigheten. Vi förklarar detta med att partiklarnas laddning bestäms av den hastighet de har när de lämnar måndammet. Vidare undersöker vi hur egenskaperna hos de reflekterade neutrala väteatomerna beror på solvindstemperaturen. Vi skapar en modell för att beskriva sambandet och använder sedan denna modell för att studera hur solvinden faller in mot månens yta när den befinner sig i jordens magnetoskikt, där jordens magnetfält orsakar en upphettning av solvindsflödet. Resultaten från dessa och andra studier använder vi sedan för att modellera solvindsreflektion från planeten Merkurius yta, för jämförelse med framtida observationer.

<p>This thesis deals with the development and calibrations of sensors to measure energetic neutral atoms (ENAs) at Mars, Venus, and the Earth. ENAs are formed in charge exchange processes between energetic, singly--charged ions and a cold neutral gas. Since ENAs can travel in long straight trajectories, unaffected by electric or magnetic fields, they can be used to remotely image plasma interactions with neutral atmospheres. ENA instrument techniques have matured over the last decade and ENA images of the Earth's ring current for example, have successfully been analyzed to extract ion distributions and characterize plasma flows and currents in the inner magnetosphere.</p><p>Three different ENA sensors have been developed to image ENAs at Mars, Venus, and the Earth. Two of them, the nearly identical Neutral Particle imagers (NPIs) are on-board the Mars Express and Venus Express spacecraft as a part of the Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3 and 4) instruments. The third is the Neutral Atom Detector Unit, NUADU, aboard the TC-2 spacecraft of the Double Star mission. The NPI design is based on a surface reflection technique to measure low energy (~0.3-60 keV) ENAs, while the NUADU instrument is based on a simple design with large geometrical factor and solid state detectors to measure high energy ENAs (~20-300 keV).</p><p>The calibration approach of both NPI sensors were to define the detailed response, including properties such as the angular response function and efficiency of one reference sensor direction then find the relative response of the other sensor directions. Because of the simple geometry of the NUADU instrument, the calibration strategy involved simulations to find the cutoff energy, geometrical factor and angular response. The NUADU sensor head was then calibrated to find the response to particles of different mass and energy. The NPI sensor for the Mars Express mission revealed a so-called priority effect in the sensor that lowers the angular resolution at high detector bias. During the calibration of the Venus Express NPI sensor tests were made which showed that the priority effect is a result of low amplitude (noise) pulses generated in the detector system. The conclusion is that the effect is caused by capacitive couplings between different anode sectors of the sensor. The thresholds on the preamplifiers were set higher on the Venus Express NPI, which removed the priority effect.</p><p>Two of the three ENA experiments, the Double Star NUADU instrument and the Mars Express NPI sensor, have successfully measured ENAs that are briefly described in the thesis. The first ENA measurements at Mars were performed with Mars Express. Initial results from the NPI include measurements of ENAs formed in the Martian magnetosheath and solar wind ENAs penetrating to the nightside of Mars. The first results from NUADU in Earth orbit show the expected ENA emissions from a storm time ring current. Also, together with the HENA instrument on the IMAGE spacecraft, NUADU have produced the first multi-point ENA image of the ring current.</p>

This thesis deals with the development and calibrations of sensors to measure energetic neutral atoms (ENAs) at Mars, Venus, and the Earth. ENAs are formed in charge exchange processes between energetic, singly--charged ions and a cold neutral gas. Since ENAs can travel in long straight trajectories, unaffected by electric or magnetic fields, they can be used to remotely image plasma interactions with neutral atmospheres. ENA instrument techniques have matured over the last decade and ENA images of the Earth's ring current for example, have successfully been analyzed to extract ion distributions and characterize plasma flows and currents in the inner magnetosphere. Three different ENA sensors have been developed to image ENAs at Mars, Venus, and the Earth. Two of them, the nearly identical Neutral Particle imagers (NPIs) are on-board the Mars Express and Venus Express spacecraft as a part of the Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3 and 4) instruments. The third is the Neutral Atom Detector Unit, NUADU, aboard the TC-2 spacecraft of the Double Star mission. The NPI design is based on a surface reflection technique to measure low energy (~0.3-60 keV) ENAs, while the NUADU instrument is based on a simple design with large geometrical factor and solid state detectors to measure high energy ENAs (~20-300 keV). The calibration approach of both NPI sensors were to define the detailed response, including properties such as the angular response function and efficiency of one reference sensor direction then find the relative response of the other sensor directions. Because of the simple geometry of the NUADU instrument, the calibration strategy involved simulations to find the cutoff energy, geometrical factor and angular response. The NUADU sensor head was then calibrated to find the response to particles of different mass and energy. The NPI sensor for the Mars Express mission revealed a so-called priority effect in the sensor that lowers the angular resolution at high detector bias. During the calibration of the Venus Express NPI sensor tests were made which showed that the priority effect is a result of low amplitude (noise) pulses generated in the detector system. The conclusion is that the effect is caused by capacitive couplings between different anode sectors of the sensor. The thresholds on the preamplifiers were set higher on the Venus Express NPI, which removed the priority effect. Two of the three ENA experiments, the Double Star NUADU instrument and the Mars Express NPI sensor, have successfully measured ENAs that are briefly described in the thesis. The first ENA measurements at Mars were performed with Mars Express. Initial results from the NPI include measurements of ENAs formed in the Martian magnetosheath and solar wind ENAs penetrating to the nightside of Mars. The first results from NUADU in Earth orbit show the expected ENA emissions from a storm time ring current. Also, together with the HENA instrument on the IMAGE spacecraft, NUADU have produced the first multi-point ENA image of the ring current.

Dans cette thèse, nous démontrons la création et la caractérisation d'états intriqués dans un ensemble atomique à l'aide d'un résonateur optique de haute finesse. Notre dis- positif expérimental consiste en une cavité fibrée placée en dessous d'une puce à atomes. Les atomes sont tous piégés dans un seul ventre du piège dipolaire créé dans la cavité. Ainsi, ils sont également couplés au mode lumineux de la cavité. Nous présentons une méthode basée sur une mesure collective et non-destructive et une évolution conditionnelle qui sert à créer des états intriqués et symétriques puis à les analyser, avec la résolution d'une particule unique, en mesurant d'une manière directe leur fonction Husimi Q. En utilisant cette méthode, nous créons et caractérisons des états W contenant jusqu'à 41 atomes. Nous reconstituons la partie symétrique de la matrice densité à partir des données expérimentales de la fonction Husimi Q en utilisant différentes méthodes de reconstruction quantique et nous obtenons une fidélité de 0.42. Par ailleurs, nous avons établi un critère d'intrication qui consiste à comparer seulement deux populations de la matrice densité. Nous l'utilisons pour déterminer le degré d'intrication présent dans les états expérimentalement créés et nous trouvons que l'état de fidélité maximale contient au moins 13 particules intriquées. Pour finir, nous présentons des résultats préliminaires concernant des expériences de dénombrement d'atomes dans la cavité en régime de mesures non-destructives ainsi que des expériences de création d'états intriqués en se servant de la dynamique Zénon quantique. / In this thesis, we demonstrate the creation and characterization of multiparticle entangled states of neutral atoms with the help of a high finesse cavity. Our experimental setup consists of a fibre-based high finesse cavity above the surface of an atom chip. It allows us to prepare an ensemble of 87Rb atoms with well-defined atom number. The atoms are trapped in a single antinode of an intracavity standing wave dipole trap and are therefore all equally coupled to the cavity mode. We present a scheme based on a collective, quantum non-destructive (QND) measurement and conditional evolution to create symmetric entangled states and to analyze them at the single-particle level by directly measuring their Husimi Q function. We use this method to create and characterize W states of up to 41 atoms. From the tomography curve of the Q function, we reconstruct the symmetric part of the density matrix via different reconstruction techniques and obtain a fidelity of 0.42. Furthermore, we have devised an entanglement criterion which only relies on comparing two populations of the density matrix. We use it to infer the degree of multiparticle entanglement in our experimentally created states and find that the state with highest fidelity contains at least 13 entangled particles. In addition, we show preliminary results on experiments to count the atom number inside a cavity in the QND regime and to create entangled states via quantum Zeno dynamics.

Ultra-cold dilute gases of neutral atoms are attractive candidates for creating controlled mesoscopic quantum systems. In particular, quantum degenerate gases of bosonic and fermionic atoms can be used to model the correlated many-body behaviour of Bose and Fermi condensed matter systems, and to study matter wave interference and coherence. This thesis describes the experimental realization and manipulation of Bose-Einstein condensates (BECs) of 87Rb and degenerate Fermi gases (DFGs) of 40K using static and dynamic magnetic atom chip traps. Atom chips are versatile modern tools used to manipulate atomic gases. The chips consist of micrometre-scale conductors supported by a planar insulating substrate, and can be used to create confining potentials for neutral atoms tens or hundreds of micrometres from the chip surface. We demonstrate for the first time that a DFG can be produced via sympathetic cooling with a BEC using a simple single-vacuum-chamber apparatus. The large 40K-87Rb collision rate afforded by the strongly confining atom chip potential permits rapid cooling of 40K to quantum degeneracy via sympathetic cooling with 87Rb. By studying 40K-87Rb cross-thermalization as a function of temperature, we observe the Ramsauer-Townsend reduction in the 40K-87Rb elastic scattering cross-section. We achieve DFG temperatures as low as T = 0.1TF , and observe Fermi pressure in the time-of-flight expansion of the gas. This thesis also describes the radio-frequency (RF) manipulation of trapped atoms to create dressed state double-well potentials for BEC and DFG.We demonstrate for the first time that RF-dressed potentials are species-selective, permitting the formation of simultaneous 87Rb double-well and 40K single-well potentials using a 40K-87Rb mixture. We also develop tools to measure fluctuations of the relative atom number and relative phase of a dynamically split 87Rb BEC. In particular, we observe atom number fluctuations at the shot-noise level using time-of-flight absorption imaging. These measurement tools lay the foundation for future investigations of number squeezing and matter wave coherence in BEC and DFG systems.

Ultra-cold dilute gases of neutral atoms are attractive candidates for creating controlled mesoscopic quantum systems. In particular, quantum degenerate gases of bosonic and fermionic atoms can be used to model the correlated many-body behaviour of Bose and Fermi condensed matter systems, and to study matter wave interference and coherence. This thesis describes the experimental realization and manipulation of Bose-Einstein condensates (BECs) of 87Rb and degenerate Fermi gases (DFGs) of 40K using static and dynamic magnetic atom chip traps. Atom chips are versatile modern tools used to manipulate atomic gases. The chips consist of micrometre-scale conductors supported by a planar insulating substrate, and can be used to create confining potentials for neutral atoms tens or hundreds of micrometres from the chip surface. We demonstrate for the first time that a DFG can be produced via sympathetic cooling with a BEC using a simple single-vacuum-chamber apparatus. The large 40K-87Rb collision rate afforded by the strongly confining atom chip potential permits rapid cooling of 40K to quantum degeneracy via sympathetic cooling with 87Rb. By studying 40K-87Rb cross-thermalization as a function of temperature, we observe the Ramsauer-Townsend reduction in the 40K-87Rb elastic scattering cross-section. We achieve DFG temperatures as low as T = 0.1TF , and observe Fermi pressure in the time-of-flight expansion of the gas. This thesis also describes the radio-frequency (RF) manipulation of trapped atoms to create dressed state double-well potentials for BEC and DFG.We demonstrate for the first time that RF-dressed potentials are species-selective, permitting the formation of simultaneous 87Rb double-well and 40K single-well potentials using a 40K-87Rb mixture. We also develop tools to measure fluctuations of the relative atom number and relative phase of a dynamically split 87Rb BEC. In particular, we observe atom number fluctuations at the shot-noise level using time-of-flight absorption imaging. These measurement tools lay the foundation for future investigations of number squeezing and matter wave coherence in BEC and DFG systems.