Suppression of Phase Decoherence in a Single Atomic Qubit

We study the suppression of noise-induced phase decoherence in a single atomic qubit by employing pulse sequences. The atomic qubit is composed of a single neutral atom in a far-detuned optical dipole trap and the phase decoherence may originate from the laser intensity and beam pointing fluctuations as well as magnetic field fluctuations. We show that suitable pulse sequences may prolongate the qubit coherence time substantially as comparing to the conventional spin echo pulse.Comment: 4 pages, 3 figure

Entrepreneurship in public administration and public policy programs in Germany and the United States

The following contribution hypothesizes that it is crucial for future professionals in public administrations and organizations to be familiar with the concepts, tools, and techniques of policy, public, and social entrepreneurship to address societal, environmental, health, and wicked problems in an innovative and sustainable way. Attention is drawn to the importance of entrepreneurship as an essential asset and feature of public administration and public policy education at higher educational institutions in Germany and the United States. The paper aims at filling a research gap because knowledge about the interrelationships between entrepreneurship and public administration and public policy education is still underdeveloped. Emphasis is put on the discussion why entrepreneurship should be incorporated in curricula and how study programs have been designed or reformed, while placing emphasis on entrepreneurship in meeting current and complex challenges in the public sector. Findings from a systematic online assessment are presented which show whether and how policy, public and social entrepreneurship are taught as an integral element of current governance and public policy study programs and what difference it makes teaching and learning wise. The findings reflect a high demand for entrepreneurship education by public administration and public policy students, on the one hand, and a low incorporation in curricula, on the other hand. Two case studies from Germany and the United States are presented which serve as good practice examples on how to transfer public, policy, and social entrepreneurship into curricula

Geometric quantum gate for trapped ions based on optical dipole forces induced by Gaussian laser beams

We present an implementation of quantum logic gates via internal state dependent displacements of ions in a linear Paul trap caused by optical dipole forces. Based on a general quantum analysis of the system dynamics we consider specific implementations with alkaline earth ions. For experimentally realistic parameters gate infidelities as low as $10^{-4}$ can be obtained.Comment: 10 pages, 4 figure

Aperiodic Ising Quantum Chains

Some years ago, Luck proposed a relevance criterion for the effect of aperiodic disorder on the critical behaviour of ferromagnetic Ising systems. In this article, we show how Luck's criterion can be derived within an exact renormalisation scheme for Ising quantum chains with coupling constants modulated according to substitution rules. Luck's conjectures for this case are confirmed and refined. Among other outcomes, we give an exact formula for the correlation length critical exponent for arbitrary two-letter substitution sequences with marginal fluctuations of the coupling constants.Comment: 27 pages, LaTeX, 1 Postscript figure included, using epsf.sty and amssymb.sty (one error corrected, some minor changes

THOR 2.0: Major Improvements to the Open-Source General Circulation Model

THOR is the first open-source general circulation model (GCM) developed from scratch to study the atmospheres and climates of exoplanets, free from Earth- or Solar System-centric tunings. It solves the general non-hydrostatic Euler equations (instead of the primitive equations) on a sphere using the icosahedral grid. In the current study, we report major upgrades to THOR, building upon the work of Mendon\c{c}a et al. (2016). First, while the Horizontally Explicit Vertically Implicit (HEVI) integration scheme is the same as that described in Mendon\c{c}a et al. (2016), we provide a clearer description of the scheme and improved its implementation in the code. The differences in implementation between the hydrostatic shallow (HSS), quasi-hydrostatic deep (QHD) and non-hydrostatic deep (NHD) treatments are fully detailed. Second, standard physics modules are added: two-stream, double-gray radiative transfer and dry convective adjustment. Third, THOR is tested on additional benchmarks: tidally-locked Earth, deep hot Jupiter, acoustic wave, and gravity wave. Fourth, we report that differences between the hydrostatic and non-hydrostatic simulations are negligible in the Earth case, but pronounced in the hot Jupiter case. Finally, the effects of the so-called "sponge layer", a form of drag implemented in most GCMs to provide numerical stability, are examined. Overall, these upgrades have improved the flexibility, user-friendliness, and stability of THOR.Comment: 57 pages, 31 figures, revised, accepted for publication in ApJ

Anharmonicity Induced Resonances for Ultracold Atoms and their Detection

When two atoms interact in the presence of an anharmonic potential, such as an optical lattice, the center of mass motion cannot be separated from the relative motion. In addition to generating a confinement-induced resonance (or shifting the position of an existing Feshbach resonance), the external potential changes the resonance picture qualitatively by introducing new resonances where molecular excited center of mass states cross the scattering threshold. We demonstrate the existence of these resonances, give their quantitative characterization in an optical superlattice, and propose an experimental scheme to detect them through controlled sweeping of the magnetic field.Comment: 6 pages, 5 figures; expanded presentatio

An AC electric trap for ground-state molecules

We here report on the realization of an electrodynamic trap, capable of trapping neutral atoms and molecules in both low-field and high-field seeking states. Confinement in three dimensions is achieved by switching between two electric field configurations that have a saddle-point at the center of the trap, i.e., by alternating a focusing and a defocusing force in each direction. AC trapping of 15ND3 molecules is experimentally demonstrated, and the stability of the trap is studied as a function of the switching frequency. A 1 mK sample of 15ND3 molecules in the high-field seeking component of the |J,K>=|1,1> level, the ground-state of para-ammonia, is trapped in a volume of about 1 mm^3

Creation of a dipolar superfluid in optical lattices

We show that by loading a Bose-Einstein condensate (BEC) of two different atomic species into an optical lattice, it is possible to achieve a Mott-insulator phase with exactly one atom of each species per lattice site. A subsequent photo-association leads to the formation of one heteronuclear molecule with a large electric dipole moment, at each lattice site. The melting of such dipolar Mott-insulator creates a dipolar superfluid, and eventually a dipolar molecular BEC.Comment: 4 pages, 2 eps figure