Using quantum physics, researchers said they communicated for the first time via a completely tap-proof telephone network in Vienna on Wednesday, according to dpa. Scientists involved in the SECOQC project, funded by the European Union, found a way to create an encryption key based on the polarisation of photons, subatomic particles that carry light. "Classic keys can be hacked by supercomputers, but not in this case," said Anton Zeilinger, a quantum physicist at the Vienna University. Until now, quantum cryptography had been achieved only between two points, but not in a network involving six participants, as in the experiment in Vienna. Under the law of quantum physics, photons change their state if they are measured in any way. For that reason, an eavesdropper listening in from outside would disturb the encoding system. Communication would break down, because the photon keys could no longer be created and distributed in the system. But the research project developed by 41 researchers in 12 countries still has its limitations. Transmission is considerably slower than over the internet. In addition, the maximum distance that data can be sent via the glass-fibre network is still limited to 100 kilometres. "As far as I am concerned, these are only technical challenges, not fundamental problems," Zeilinger said. "I think we will be able to offer secure communication to our customers in three to four years," said Brigitte Ederer, the CEO of Siemens AG Austria, which is involved in the project. Before selling the system to governments or financial institutions, Siemens aims to lower its cost to 10,000 euros (13,600 dollars), from currently 100,000 euros.
