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We report on transport operations with linear crystals of 40 Ca + ions by applying complex electric time-dependent potentials. For their control we use the information obtained from the ions' fluorescence. We demonstrate that by means of this feedback technique, we can transport a predefined number of ions and also split and unify ion crystals. The feedback control allows for a robust scheme, compensating for experimental errors as it does not rely on a precisely known electrical modeling of the electric potentials in the ion trap beforehand. Our method allows us to generate a self-learning voltage ramp for the required process. With an experimental demonstration of a transport with more than 99.8 % success probability, this technique may facilitate the operation of a future ion based quantum processor.

Longitudinal sputtering hollow cathode discharge (HCD) used as active medium for lasing is studied by means of numerical modelling. Due to the longitudinal non-uniformities of the discharge, the laser operation could be strongly affected. The non-uniformity of the discharge is mainly influenced by the dimensions of the hollow cathode, in particular by the aspect ratio length/radius. To study the geometrical features, a simulation model for HCDs has been constructed using the Plasimo modelling platform. The model allows in-depth studies of the plasma mechanisms and enables finding the optimum under the working conditions of the HCDs. The model is validated by comparing the results with the experimental observations. The spatial distribution of the plasma density and potential as well as an in-depth discussion of the results and the trends revealed by the model are presented. The proper understanding of the essential geometrical features allowed defining the optimal aspect ratio length/diameter for stable and uniform discharge with high excitation efficiency.

An ultrashort pulse propagating in a resonant dense atomic medium experiences an important distortion due to a strong modification of its spectral phase. This distortion cannot be corrected using the usual simple dispersive devices (a pair of prisms, gratings, etc). We present here an experimental demonstration of the compensation of this effect using a dual 640-pixel high resolution pulse-shaper device. A cross-correlation intensity measurement combined with the XFROG (Cross-correlated Frequency Resolved Optical Gating) spectral phase measurement of the compensated pulse are performed; efficient correction of the resonant dispersive phase is shown. A spectacular temporal compression of the propagating pulse is then obtained.