In this paper recent experiments with the one-atom maser or micromaser performed by our group will be reviewed, as well as experiments with single ions in traps. The discussion is limited to results relevant in connection with the experimental realization of a quantum computer. The principle of the electrode configuration of the ion trap used for the investigation of the spectrum of resonance fluorescence described in the second part of this paper has also been used to realize a linear trap. This work on resonance fluorescence and the more recent work on ordered structures in a miniature trap being produced recently are the basis for the use of such a set-up for quantum computers.
We report on the alteration of photon-emission properties of a single trapped ion coupled to a high-finesse optical fiber cavity. We show that the vacuum field of the cavity can simultaneously affect the emissions in both the infrared (IR) and ultraviolet (UV) branches of the $\mathrm{\ensuremath{\Lambda}}$-type level system of
40Ca+ despite the cavity coupling only to the IR transition. The cavity induces strong emission in the IR transition through the Purcell effect resulting in a simultaneous suppression of the UV fluorescence. The measured suppression of this fluorescence is as large as 66% compared with the case without the cavity. Through analysis of the measurement results, we have obtained an ion-cavity coupling of ${\overline{g}}_{0}=2\ensuremath{\pi}\ifmmode\times\else\texttimes\fi{}(5.3\ifmmode\pm\else\textpm\fi{}0.1)$ MHz, the largest reported so far for a single ion in the IR domain.