Future fibre networks to exceed light speed?

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Munir Kotadia ZDNet Australia

Published: 16 Aug 2007 13:39 BST

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German scientists claim to have broken the light-speed barrier, which could blow away the known limitations of modern networking, but the technology is unlikely to make it into a product — if at all — until most administrators working today have retired.

Exceeding the speed of light, approximately 300,000km per second, is supposed to be completely impossible. According to Einstein's special theory of relativity, it would take an infinite amount of energy to accelerate an object through the light barrier.

But two German physicists claim to have forced light to overcome its own speed limit using the strange phenomenon known as "quantum tunnelling".

Gunter Nimtz, one of the physicists from the University of Koblenz, told New Scientist magazine: "For the time being, this is the only violation of special relativity that I know of."

However, the scientists' claims should be treated with some scepticism until they have been investigated by the wider scientific community, according to Dr Kevin McIsaac, an analyst at Sydney-based firm IBRS, who holds a PhD in theoretical atomic physics.

"From time to time we do hear about these interesting experiments, often by well-meaning scientists. But, until this has been validated by the scientific community, you want to treat it with some scepticism," said McIsaac.

"To date, all indications are that no information can travel faster than the speed of light. There are some experiments that indicate you can have interactions that appear to be faster than the speed of light but you still can't transmit information faster than the speed of light," said McIsaac.

The scientists set up an experiment in which microwave photons — energetic packets of light — appeared to travel "instantaneously" between two prisms forming the halves of a cube placed a metre apart.

When the prisms were placed together, photons fired at one edge passed straight through them, as expected. After they were moved apart, most of the photons reflected off the first prism they encountered and were picked up by a detector. But a few photons appeared to "tunnel" through the gap separating them as if the prisms were still held together.

Although these photons had travelled a longer distance, they arrived at their detector at exactly the same time as the reflected photons. In effect, they seemed to have travelled faster than light.

Quantum tunnelling is a well known phenomenon that occurs as a direct result of the strange uncertainty which pervades nature at very small scales. It allows subatomic particles to break apparently unbreakable barriers.

Even if the discovery turns out to be real, IBRS's McIsaac isn't convinced that it could be turned into a useful product: "About 15 or 20 years ago a scientist claimed to have discovered cold fusion... but still nothing has happened. One of the big promises has been quantum computing and we still don't have it. Also, photonic computing — we still don't have that either."

"So, frankly, I would suggest that anybody who is an administrator today probably won't see this till they have retired," McIsaac said.

Quantum tunnelling
To understand the principle of quantum tunnelling, consider a ball being bowled up a hill. If the ball has insufficient velocity, it will not roll over the top of the hill and appear on the other side. But, if the ball was a subatomic particle, subject to quantum laws, it would also behave like a wave.

The "wave function" describing the particle would represent the probability of finding it at a certain location. This wave could extend to the other side of the hill, meaning there will always be a small possibility of the particle being detected there unexpectedly.

When this happens it is as if the particle has "tunnelled" through the hill.

The effect is already used in a practical way in the scanning tunnelling microscope, which can image surface features at an atomic scale and relies on the "tunnelling" of electrons.

Tunnelling is also involved in radioactivity and nuclear fusion. Without it, the sun could not shine, and some scientists believe the universe itself only came into existence because of tunnelling.

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