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THE world’s tiniest transmitter and receiver is operating in Austria. Using
trapped barium ions, researchers at the University of Innsbruck have sent single
photons from one to another via a mirror (Nature, vol 413, p 495).
Since an ejected photon reveals the state of the atom that emitted it, the
technique could let physicists peer inside individual atoms. It could also lead
to networks that exploit the quantum nature of particles to carry out tasks like
encryption. “This may be feasible using individual atoms and photons,” says team
member Jürgen Eschner.