No abstract available

[en] In the last few years significant progress has been achieved both in the experimental technique and the theoretical methods for the determination of the energy levels of simple hydrogenic systems. We review recent two-photon spectroscopic measurements performed in Garching and the relevant theoretical predictions for the hydrogen energy levels. Good agreement is achieved when all theoretical contributions are included, showing the importance of recently calculated higher order corrections. (Author)

[en] We report on new precision measurements of the 1S ground state Lamb shift in hydrogen and deuterium, based on a direct frequency comparison of the 1S-2S and 2S-4S two-photon resonances. By observing the 2S-4S transition via blue Balmer-β fluorescence we are now surpassing the accuracy of the 2S Lamb shift. Our results of 8172.86(6) MHz for hydrogen and 8184.00(8) MHz for deuterium are not in perfect agreement with the theoretical predictions of 8173.12(6) and 8184.13(6) MHz, respectively. We also derive values for the Rydberg constant and the electron-proton mass ratio

[en] In this paper the second-order nuclear structure correction to the energy of hydrogenlike systems is estimated and previous results are corrected. Both deuterium and hydrogen are considered. In the case of deuterium the correction is proportional to the nuclear polarizability and amounts to about -19 kHz for the 1S state. For hydrogen the resulting energy shift is about -60 Hz

[en] Two-photon spectroscopy of the hydrogen 1S-2S transition in a cold atomic beam has reached a resolution Δν/ν of 1 part in 10¹¹ in hydrogen and 7 parts in 10¹² in deuterium. The hydrogen and deuterium 1S-2S transition frequencies have been determined with a precision of 1 part in 10¹¹. This leads to an accurate value for the Rydberg constant, while the 1S Lamb shift and the isotope shift are determined with order of magnitude improvements over previous measurements. We describe in detail the 1S-2S spectrometer, calculate the line shape of the resonance, and compare it to the experimental data

[en] We have observed the 1S-2S transition of atomic hydrogen with a resolution of 5 parts in 10¹¹ by means of Doppler-free two photon spectroscopy in an atomic beam. The significantly asymmetric line shape is strongly affected by the relativistic Doppler effect. The new high resolution can be used for improved measurements of the Rydberg constant, the 1S Lamb shift, and the isotope shift of hydrogen and deuterium

No abstract available

[en] Methods for, and limitations to, the generation of entangled states of trapped atomic ions are examined. As much as possible, state manipulations are described in terms of quantum logic operations since the conditional dynamics implicit in quantum logic is central to the creation of entanglement. Keeping with current interest, some experimental issues in the proposal for trapped-ion quantum computation by J.I. Cirac and P. Zoller (University of Innsbruch) are discussed. Several possible decoherence mechanisms are examined and what may be the more important of these are identified. Some potential applications for entangled states of trapped-ions which lie outside the immediate realm of quantum computation are also discussed

No abstract available

[en] Many efforts are currently underway to build a device capable of large scale quantum information processing (QIP). Whereas QIP has been demonstrated for a few qubits in several systems, many technical difficulties must be overcome in order to construct a large-scale device. In one proposal for large-scale QIP, trapped ions are manipulated by precisely controlled light pulses and moved through and stored in multizone trap arrays. The technical overhead necessary to precisely control both the ion geometrical configurations and the laser interactions is demanding. Here we propose methods that significantly reduce the overhead on laser-beam control for performing single- and multiple-qubit operations on trapped ions. We show how a universal set of operations can be implemented by controlled transport of ions through stationary laser beams. At the same time, each laser beam can be used to perform many operations in parallel, potentially reducing the total laser power necessary to carry out QIP tasks. The overall setup necessary for implementing transport gates is simpler than for gates executed on stationary ions. We also suggest a transport-based two-qubit gate scheme utilizing microfabricated permanent magnets that can be executed without laser light