The storage and manipulation of single atoms or ions in a cavity can allow for the sensitive probing of the interactions of light and matter. Recent work has also shown that a discrete number of trapped atoms can be manipulated coherently with light so that the states become quantum-mechanically entangled, which could be of use in quantum computing. However, the short dwell times of the atoms within cavities (typically fractions of a millisecond) are a serious limitation. Fischer et al. show that a feedback mechanism can be used to keep an atom in the cavity about 30% longer than conventional constant-intensity light-trapping potentials permit. As the atom enters the cavity, the interaction between the atom and the light field is monitored. When an atom is detected, the intensity of the light is dynamically adjusted so that the trapping light field momentarily puts the brakes on atom motion in the cavity. In this setup, the same laser detects and manipulates the atom; further improvements are anticipated by splitting these functions between two lasers.—ISO
Phys. Rev. Lett.88, 163002 (2002).