Wormholes could end messy wiring and speed up computers

Last Updated: 2:01pm GMT 19/11/2007

Yet another strange sci fi possibility is raised by research on bizarre "metamaterials," reports Roger Highfield

A version of the wormholes that have long inspired science fiction writers could one day be used in the home to provide invisible cables to wire up electronics or provide three dimensional images.

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Conventional wormholes result from playing with Einstein's theory of relativity and provide, in effect, tunnels that connect remote regions in space and time.
Science-fiction: An artist's impression of a wormhole
Although researchers are scratching their heads over how to make one in practice, they have become a staple of science fiction because they permit time travel and create short cuts across intergalactic space.

Now a more prosaic kind of wormhole, one that transmits light invisibly, perhaps even between remote regions, has been devised by Profs Allan Greenleaf of the University of Rochester in New York state, Yaroslav Kurylev of University College, London, Matti Lassas of the Helsinki University of Technology, and Gunther Uhlmann of the University of Washington, Seattle.

Described in the journal Physical Review Letters, these 'electromagnetic wormholes' are the electromagnetic radiation (light) based equivalent of space-time wormholes and could function as invisible light-carrying cables.

If you were to gaze down one end of such a wormhole, sitting on a nearby table, you could find yourself gazing through a tube at your garden, for example.

The clever thing is that this tube would be invisible, hence a proposal to use it to create three dimensional video displays, albeit with a limited viewing angles. There may be more exotic applications too, in superfast computers that rely on light and improved body scanners.

Although the wormhole designs are at present theoretical, the technologies for making them already exist and are being studied to make invisibility shields which can cloak objects by bending light around them.

Prof Greenleaf and his colleagues envisage all kinds of possible applications in areas ranging from information technology to medicine.

"It's a cool idea," Nature was told by physicist Prof Ulf Leonhardt at the University of St Andrews, Scotland, who came up with one proposal for invisibility along with others at Duke University, North Carolina, and Imperial College London.

The wormholes, like the invisibility cloaks, would be made from 'metamaterials', structures engineered at the atomic level to interact with light in odd ways.

These interact with the electromagnetic field of a light beam to create unusual optical effects, such as a negative refractive index - the light is bent the 'wrong' way as it passes through.

Prof Greenleaf's team has worked out how to customise the shape and properties of a metamaterial tube so that light from the outside bends around it, making it invisible, while light inside bounces along the channel as if whizzing along inside an optical fibre.

"We chose the name because the metamaterial construction will trick the electromagnetic waves in the vicinity of the wormhole into behaving as though they were propagating on a different space than standard three-dimensional space."

In this way, light entering one end of the wormhole would be visible at the other end. However, the wormhole is very short, it acts rather like a fish eye lens, he says.

However, while creating an invisibility shield is already a big challenge a wormhole would be harder still. "Metamaterials for optical frequencies (as opposed to those for microwaves, which have been around for a number of years) are still in their infancy and there needs to be enormous progress in their fabrication and assembly in order to have any hope of making a usable three-dimensional cloak or wormhole," says Prof Greenleaf.

"Assembling a three-dimensional device, as opposed to the two dimensional cloak demonstrated by the team at Duke last year, would be technically challenging, and making three-dimensional measurements of the electromagnetic fields so as to verify that the wormhole was acting as claimed might be even more difficult," said Prof Greenleaf."

And he said that the metamaterial wormhole will only function over a fairly narrow range of frequencies, such as specific colours of light. "Observed at other frequencies, it would just look like a large cylinder covered with odd-looking material."

Sir John Pendry, who is working on invisibility at Imperial College London, commented: "A wormhole is one of several amazing constructs enabled by transformation optics, the new design tool developed by ourselves and David Smith at Duke.

"Another example of something exotic is the ability to make 'negative' optical materials that effectively eliminate the distance between two objects. Two people on opposite sides of a room might appear to be standing next to one another if a slab of 'negative' material were placed between them."