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Like all the best new technologies, quantum computing has been dismissed by some of the greatest thinkers of the age. Gordon Moore, the co-founder of Intel and author of Moore's Law, said recently that quantum computers are a dream and will never be built.

Moore may be right, but the promise of quantum computing - using the strange behaviour of subatomic particles to form the basis of powerful new applications - has proved too alluring for some.

"Quantum computing, although a long way off, threatens the basis of security for a lot of commerce today. Those with quantum computers would be able to see everything. That would be the hacker's killer app," says Martin Illsley of IT consultancy and services giant Accenture.

"Quantum computing will happen. It is probably 20 years away, but it could be here in 10. The main point is that you don't want to bet on that. We should be ensuring the door is closed before it is even opened." Accenture is one of a growing group of companies that believes that another branch of physics - quantum cryptography - holds the potential to address security concerns and demands immediate investment. Unlike quantum computing, quantum cryptography is here today, and is actually being piloted.

Quantum cryptography encodes photons - tiny 'packets' of light - and makes use of the 'uncertainty principle' to ensure that encryption keys have not been tampered with. The principle means that, at this subatomic level, it is impossible for anyone to observe the photons without disturbing their state This disturbance is used to destroy the keys and prevent eavesdropping. As a result, a message can be made 100% tamper-proof.

Using the technology, it is possible to send new encoding and deciphering keys, automatically, twice a second, dramatically increasing security, and simultaneously automating the currently slow and manual process of using dual encryption keys. A further benefit: all the numbers it generates are genuinely random, further strengthening the keys.

Several banks, including Visa, and the US DARPA defence network are among those to have built trial networks using quantum cryptography. These organisations admit that much work is to be done before quantum cryptography is used by a wider audience. To work effectively, for example, both the photon transmitters and receivers need to be much improved.

One limitation is that photons suffer from interference when sent over more than 80 kilometres of optic cables, severely limiting the technology's application. And while normal networks can use repeaters, this is not so easy with photons - any attempt to measure the signal will destroy its integrity. Line of sight wireless transmissions, meanwhile, are restricted to a few kilometres, although satellite transmission may soon be possible.

All of these limitations are the focus of intense research efforts, and progress in the past four years has been rapid. Last year, in an attempt to defend itself against electronic snooping by the US and other governments, the European Union agreed to invest E11 million on the development of a secure communication system based on quantum cryptography. Some researchers think that the widespread commercial adoption will naturally follow.

If quantum cryptography does enable 100% secure messaging, that will undoubtedly stir up a political debate. The equipment to manufacture the transmitters and receivers is large and expensive - making it possible, but politically controversial, for governments to prevent or slow down the widespread proliferation of the products.