NEC and Mitsubishi Electric have claimed another important breakthrough in the use of quantum principles to secure computer communications - they’ve managed to interconnect cryptographic systems from different vendors for the first time.

Researchers at the University of Tokyo’s Institute of Industrial Science were able to verify that the two systems were functioning correctly by conducting an eavesdropping experiment.

As is a certainty in any properly working quantum cryptographic system, the eavesdropping was successfully detected. Data was also passed over a distance of 200 kilometres at an unspecified data rate.

The companies claim the inter-connection is significant, because any commercial development of quantum cryptography for real-world applications will depend on such interoperability.

It has been an eventful year for the field. Last month The National Institute of Standards and Technology (NIST) said it had broken the world record for data transfer across a quantum cryptographic system, reaching a throughput of 4 million bits per second across a 1 km-long fibre link.

Quantum cryptography has excited considerable interest in the US, Japan and the UK, with a number of universities pioneering its application using state funds. The promise is a network that can send data using "quantum-state photons" with a 100 percent guarantee that any attempt to break the encryption can be detected.

This is not possible with conventional cryptography systems, which depend on the theoretical and computing complexity of a specified algorithm. Quantum systems are not, therefore, necessarily harder to break, but the laws of quantum physics assure that any tampering can be found out.

As time passes, there is a danger that quantum cryptography will have to contend with more and more headline-driven science reporting, where teams compete to announce 'breakthroughs' in order to keep research funds coming. However, it looks as if real advances are now being made.

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