Radio communication is now possible on the most elementary level: scientists at the ETH Zurich and the Max Planck Institute for the Science of Light in Erlangen have used two molecules as antennas and transmitted signals in the form of single photons, i.e. light particles, from one to the other.
Since a single photon usually has very little interaction with a molecule, the physicists had to use a few experimental tricks for the receiver molecule to register the light signal. A radio connection established via individual photons would be ideal for various applications in quantum communication – in quantum cryptography or in a quantum computer, for example.
Individual particles of light are the means of choice to transmit quantum bits. In the future, the smallest units of quantum information could replace the conventional bits if the computer advances into new dimensions of computing speed with the aid of the special properties of quantum physics. In quantum cryptography, single photons are already being used as information carriers which cannot be intercepted without this being noticed - in banking data exchange, for example.
In experiments conducted at the ETH Zurich, physicists working with Vahid Sandoghdar, who recently became Director of the Nano-optics Department at the Max Planck Institute for the Science of Light and holds a Humboldt professorship at the University of Erlangen, have transmitted single photons between the smallest antennas in the world, i.e. between two molecules of dibenzanthanthrene (DBATT). "The difficulty with this experiment is that normally a single photon hardly interacts at all with a molecule," explains the Max Planck Director.