Researchers at the University of Bonn, Germany, presented a new method to develop quantum repeaters that can pass quantum information over long distances, by utilizing Purcell effect with which light particles can be shot in a much more targeted manner.
When a laser beam is allowed to fall on an atom, the light photons will be absorbed by the atom and it will be excited to a higher energy state, provided the energy difference between the levels of the atom matches with the energy of the incident light. The atom, after its lifespan in the excited state, will emit this extra energy and it will be deexcited to the ground state with the emission of a photon. However, the direction in which this emitted photon travels is purely coincidental.
To force the emitted photons to travel along the desired direction, the researchers of Bonn University, Germany, made use of an interesting phenomenon in physics, known as Purcell effect, the existence of which was already proven. The Purcell effect is the enhancement of a quantum system's emission rate by modifying and adjusting its environment. The German scientists modified the experimental enviroment by placing rubidium atom between two parallel mirrors, and irradiated it with an intense laser beam. It was found that the photons emitted during the deexcitation of rubidium atom prefers to travel towards one of the mirrors.
This discovery shows that it is possible to utilize Purcell effect for the targeted emission of photons from neutral atoms. Hence it would be useful in future, in developing quantum repeaters for long distance quantum information transmission, as the signal has to be buffered to assure the signal quality for great distances.