Laser experiments with single atoms and the test of basic physics

The interaction of a single Rydberg atom with a single mode of the electromagnetic field and the resonance fluorescence of a single atomic ion stored in radio-frequency trap were investigated. In the former experiment, the quantum collapse and revival of the atomic inversion predicted by the Jaynes-Cummings model could be demonstrated for the first time. In the latter experiment, antibunching and sub-Poissonian photon statistics were detected in the fluorescent light. Furthermore the observation of the crystallization of few ions in a trap is described. Since the stored ions can be cooled by the laser light and heated by the radio frequency field of the trap, subsequent phase transitions could be observed.