Prototype network unveiled.

Researchers behind the world's largest quantum encrypted network said the technology could secure business networks inside six years.

The prototype Quantum Key Distribution network was built by the Secure Communication based on Quantum Cryptography group and is described in a journal paper published by the Institute of Physics this week.

It was used for secure tele and videoconferencing between six Siemens locations in Vienna between last May and November.

In quantum cryptography, communications were encrypted in such a way as to make it impossible to eavesdrop without altering the key.

The network was based on the "trusted-repeater paradigm", and distributed a key along the network through nodes. At each node, the key was re-encrypted and retransmitted until it reached its destination.

"The advantage of this approach is its modularity," said lead author Momtchil Peev. "The prototype design is completely scalable."

Peev highlighted the network's tight integration as one of its most important achievements, along with the performance and stability of its eight nodes.

It consistently performed at a minimum of 1Kbps over 25 kilometres and Peev said, "nothing unexpected happened during operation".

He expected more such networks in coming years after developments in enabling this technology, traffic engineering and telecommunications infrastructures.

"In five to six years, perhaps a number of metropolitan area networks would start emerging and then the business impact would cease to be marginal," he said.

The project is funded by the European Commission. It involves 41 research and industrial organisations from the EU, Switzerland and Russia, including Siemens, Hewlett-Packard, Toshiba, Cambridge University and Austrian Research Centers GmbH.