Collinear helium under periodic driving: stabilization of the asymmetric stretch orbit

The collinear eZe configuration of helium, with the electrons on opposite sides of the nucleus, is studied in the presence of an external electromagnetic (laser or microwave) field. We show that the classically unstable "asymmetric stretch" orbit, on which doubly excited intrashell states of helium with maximum interelectronic angle are anchored, can be stabilized by means of a resonant driving where the frequency of the electromagnetic field equals the frequency of Kepler-like oscillations along the orbit. A static magnetic field, oriented parallel to the oscillating electric field of the driving, can be used to enforce the stability of the configuration with respect to deviations from collinearity. Quantum Floquet calculations within a collinear model of the driven two-electron atom reveal the existence of nondispersive wave packets localized on the stabilized asymmetric stretch orbit, for double excitations corresponding to principal quantum numbers of the order of N > 10.Comment: 13 pages, 12 figure

Physics through the 1990s: Atomic, molecular and optical physics

The volume presents a program of research initiatives in atomic, molecular, and optical physics. The current state of atomic, molecular, and optical physics in the US is examined with respect to demographics, education patterns, applications, and the US economy. Recommendations are made for each field, with discussions of their histories and the relevance of the research to government agencies. The section on atomic physics includes atomic theory, structure, and dynamics; accelerator-based atomic physics; and large facilities. The section on molecular physics includes spectroscopy, scattering theory and experiment, and the dynamics of chemical reactions. The section on optical physics discusses lasers, laser spectroscopy, and quantum optics and coherence. A section elucidates interfaces between the three fields and astrophysics, condensed matter physics, surface science, plasma physics, atmospheric physics, and nuclear physics. Another section shows applications of the three fields in ultra-precise measurements, fusion, national security, materials, medicine, and other topics

The bound mu+ mu- system

We consider the hyperfine structure, the atomic spectrum and the decay channels of the bound mu+ mu- system (dimuonium). The annihilation lifetimes of low-lying atomic states of the system lie in the nanosecond range range. The decay rates could be measured by detection of the decay products (high energy photons or electron-positron pairs). The hyperfine structure splitting of the dimuonic system and its decay rate are influenced by electronic vacuum polarization effects in the far time-like asymptotic region. This constitutes a previously unexplored kinematic regime. We evaluate next--to-leading order radiative corrections to the decay rate of low-lying atomic states. We also obtain order alpha^5 corrections to the hyperfine splitting of the 1S and 2S levels.Comment: 10 figures (eps format) attached, Scheduled tentatively by PRA for Nov/Dec 199

Theory of Microwave to Optical Photon Upconversion Using Erbium Doped Crystals

The subject of this thesis is coherent conversion from microwave photons to optical photons. This has applications for quantum computing, and would allow interfacing between superconducting qubits and optical fibres. Specifically, we will focus on photon conversion via erbium ions in a doped crystal. We model a device which has an erbium doped crystal inside overlapping microwave and optical cavities. Input microwave photons are combined with photons from an optical pump laser via interactions with the erbium ions. This will produce optical output photons carrying the same quantum information as the input microwave photons. We develop a description of the interaction between the atoms and the light fields, accounting for both loss effects in the single atoms, and inhomogeneous broadening of the ensemble. Our theory is compared with experimental data, and shows good agreement. We explore various phenomena which arise in this system, including the effects of temperature and microwave power. It is shown that the description of this device from earlier work is not valid in the regime where the conversion efficiency is greatest. Hence, this work is necessary to be able to predict the maximum conversion efficiency. We develop a linearised model which is accurate in the regime where the microwave and optical fields are small, such as the regime used for quantum information. This model is used to maximise the photon number conversion efficiency of the device. We predict conversion efficiencies above 20%, far higher than has been achieved experimentally with using rare earth ions. Modifying our device should further increase the conversion efficiency to above 80%

Spectral properties of planar helium under periodic driving

We present an original method for the accurate quantum treatment of the planar three body Coulomb problem under electromagnetic driving. Our ab initio approach combines Floquet theory, complex dilation, and the representation of the Hamiltonian in suitably chosen coordinates without adjustable parameters. The resulting complex-symmetric, sparse banded generalized eigenvalue problem of rather high dimension is solved using advanced techniques of parallel programming. In the present thesis, this theoretical/numerical machinery is employed to provide a complete description of the bound and of the doubly excited spectrum of the field-free 2D helium atom. In particular, we report on frozen planet quantum states in planar helium. For the driven atom, we focus on the near resonantly driven frozen planet configuration, and give evidence for the existence of nondispersive two-electron wave packets which propagate along the associated periodic orbit. This represents a highly nontrivial qualitative confirmation of earlier calculations on a 1D model atom, though with important enhancements of the decay rate of these atomic eigenstates in the field, due to the transverse decay channel. The latter is already found to enhance the decay rates of the unperturbed frozen planet as compared to the 1D model, in surprisingly good quantitative agreement with 3D results.Wir stellen eine originelle Methode zur akkuraten quantenmechanischen Behandlung des planaren Drei-Koerper-Coulombproblems in Gegenwart eines elektromagnetischen Feldes vor. Unser ab initio Zugang vereint Floquet-Theorie, komplexe Dilatation und die Darstellung des Hamilton-Operators in geeignet gewaehlten Koordinaten -- ohne freie Parameter. Das resultierende, durch eine komplex-symmetrische, duenn besetzte Bandmatrix dargestellte verallgemeinerte Eigenwertproblem vergleichsweise grosser Dimension wird mittels fortgeschrittener Methoden paralleler Programmierung geloest. In der vorliegenden Dissertation wird dieser theoretisch/numerische Apparat zur vollstaendigen Charakterisierung des gebundenen sowie des doppelt angeregten Spektrums des feldfreien zweidimensionalen Heliumatoms genutzt. Insbesondere untersuchen wir die frozen planet-Konfiguration in planarem Helium. Bei dem durch ein aeusseres Feld gestoerten Atom konzentrieren wir uns auf die nahresonant getriebene frozen planet-Konfiguration und stellen erste Ergebnisse vor, welche die Existenz nichtdispergierender Wellenpakete nahelegen, die entlang des korrespondierenden klassischen Orbits propagieren. Hierbei handelt es sich um eine hoch nichttriviale Bestaetigung frueherer Ergebnisse fuer ein eindimensionales Modellatom, bei freilich merklicher Ueberhoehung der Zerfallsrate der atomaren Eigenzustaende im Feld -- aufgrund des zusaetzlich verfuegbaren, transversalen Zerfallskanals. Letzterer macht sich bereits durch eine Ueberhoehung der Zerfallsraten des ungestoerten frozen planet im Vergleich zum eindimensionalen Modell bemerkbar, in ueberraschend quantitativer Uebereinstimmung mit den Ergebnissen dreidimensionaler Rechnungen

Light-Matter Interaction in Hybrid Quantum Plasmonic Systems

Attempting to implement quantum information related applications utilizing atoms and photons, as they naturally form quantum systems supporting superposition states, hybrid quantum plasmonic systems emerged in the past as a platform to study and engineer light-matter interaction. This platform combines the unrivaled electromagnetic field localization of surface plasmon polaritons, boosting the light-matter coupling rate, with the tremendous integration potential of truly nanoscale structures, and both the significant emission rates of nanoantennas and photonic transmission velocities. In this work, a classical description of surface plasmon polaritons is combined with a light-matter interaction model based on a cavity quantum electrodynamical formalism. The resulting composite semi-classical method, introduced and described in this thesis, provides efficient and versatile means to simulate the dynamical behavior of radiative atomic transitions coupled to plasmonic cavity modes in the weak incoherent coupling regime. Both the emission into the far field and various dissipation mechanisms are included by expanding the model to an open quantum system. The variety of light-matter interaction applications that can be modeled with the outlined method is indicated by the four different exemplary scenarios detailed in the application chapter of this thesis. The classical description of localized surface plasmon polaritons is benchmarked by reproducing the experimental measurements of the molecular fluorescence manipulation through optical nanoantennas in a collaborative effort with experimental partners. Furthermore, in the weak light-matter coupling regime, the potential of achieving a higher nanoantenna functionality and simultaneously realizing more elaborate quantum dynamics is revealed by the three remaining applications. Each pivotally involving a bimodal nanoantenna and demonstrating different quantum optical phenomena, the implementation of cavity radiation mode conversion, non-classical cavity emission statistics, and non-classical cavity emission properties is shown and described in the application chapter

Precision measurement and symmetry properties of metastable hydrogen

Includes bibliographical references.2022 Fall.Hydrogen has been an indispensable system to study during the development of quantum mechanics due to the simplicity of its atomic structure. Hydrogen maintains its utility today as an important tool for determining fundamental values such as the Rydberg and fine structure constants, as well as the proton charge radius. The work described in this thesis aims to use hydrogen for determining the proton Zemach radius, to search for anomalous spin-dependent forces, and to provide means for measuring the degree of parity violation within this simple system. An overview of a 2S1/2 hyperfine interval measurement is described, followed by a description of the apparatus used and finally a discussion of the systematic effects to be characterized. A proposed parity violation experiment is also described

Towards synthetic Rydberg lattices with optical tweezer arrays

Trapped neutral atoms in optical tweezers have emerged as a viable platform for quantum simulation, metrology and quantum information processing due to their simple design yet versatile application. Recent developments in loading, cooling and re-arrangement techniques have been combined with Rydberg interactions and have led to insightful studies of quantum many-body phenomena based on analog simulation of Ising and XY models. So far, such systems have mostly been limited to interactions that involve one or two Rydberg states. Concurrently, synthetic lattices have also emerged as a viable platform for quantum simulation of many-body systems through site-by-site engineering of many-body Hamiltonians. Synthetic lattices feature both full spectroscopic control and tunability of every single-body term in the simulated Hamiltonian and thereby enable a bottom-up approach to studying emergent phenomena when combined with interactions. In our experiment, we bring the idea of synthetic lattices to a system of potassium atoms trapped in optical tweezer arrays, where tweezer-trapped atoms are excited to a Rydberg state followed by applying multi-tone microwave fields to drive transitions to neighboring Rydberg levels. While such a synthetic lattice can be used to study topology and disorder in 1D, our system allows us to bring Rydberg interaction into the picture and study the interplay between topology, disorder and interactions. One novel phenomenon that has been identified to appear in such a system is the spontaneous formation of quantum strings in the synthetic dimension. This work also presents some technical studies on cooling and imaging of single atoms in optical tweezers in preparation for Rydberg excitation. Specifically, we demonstrate a simple approach to in-trap imaging which involves using a near-detuned (780 nm) optical tweezer, which leads to relatively minor differential (ground vs. excited state) Stark shifts. We demonstrate that simple and robust loading, cooling, and imaging can be achieved through a combined addressing of the D1 (770 nm) and D2 (767 nm) transitions. While imaging on the D2 transition, we can simultaneously apply Λ-enhanced gray molasses (GM) on the D1 transition, preserving low backgrounds for single-atom imaging through spectral filtering. Using D1 cooling during and after trap loading, we demonstrate enhanced (75%) loading efficiencies as well as cooling to low temperatures (≈ 15 μK). These results suggest a simple and robust path for loading and cooling large arrays of potassium atoms in optical tweezers, through the use of resource-efficient near-detuned optical tweezers and GM cooling