QUANTUM MECHANICS:
Physicists Tame a Single Photon
Andrew Watson
Achieving the phenomenon known as quantum nondemolition--the repeated measurement of a quantum state without destroying it, as quantum mechanics dictates should be possible--is extremely difficult because of the fragile nature of quantum states. But in this week's issue of Nature, a team of French physicists reports trapping a single photon between spherical niobium mirrors and repeatedly detecting it with a single rubidium atom without destroying it. Physicists have hailed the work as a triumph of quantum measurement.