Cavity Quantum Electrodynamics; April 1993; Scientific American
Magazine; by Serge Haroche and Jean-Michel Raimond; 8 Page(s)
Fleeting, spontaneous transitions are ubiquitous in the quantum
world. Once they are under way, they seem as uncontrollable and
as irreversible as the explosion of ¿reworks. Excited atoms, for
example, discharge their excess energy in the form of photons
that escape to infinity at the speed of light. Yet during the
past decade, this inevitability has begun to yield. Atomic
physicists have created devices that can slow spontaneous
transitions, halt them, accelerate them or even reverse them
entirely. Recent advances in the fabrication of small
superconducting cavities and other microscopic structures as
well as novel techniques for laser manipulation of atoms make
such feats possible. By placing an atom in a small box with
reflecting walls that constrain the wavelength of any photons it
emits or absorbs--and thus the changes in state that it may
undergo--investigators can cause single a