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Saturday, November 20, 2010

The space-time cloak

Researchers from Imperial College London have thought of a way to use metamaterials to construct what they call a ‘space-time cloak’ that could conceal events.

Metamaterials are artificial materials that distort light or sound waves in particular ways. Martin McCall and his team got the idea of using metamaterials to speed up or slow down light. Light ordinarily varies in speed as it passes through different materials. By carefully controlling that speed, a window of invisibility can be created.

As McCall explains:

The leading half of the light speeds up and arrives before an event, whilst the trailing half is made to lag behind and arrives too late. The result is that for a brief period the event is not illuminated, and escapes detection.

Credit: Imperial College London

Although the researchers suggests that such a device could create the illusion of transporting people or objects instantaneously, a more likely usage would be in signal processing. For example, the space-time cloak could be used to temporarily interrupt a data channel in order to conduct a priority calculation. To an observer, it would appear as if there had been no interruption.

Alberto Favaro, a researcher on the project, gives the following analogy:

Imagine computer data moving down a channel to be like a highway full of cars. You want to have a pedestrian crossing without interrupting the traffic, so you slow down the cars that haven't reached the crossing, while the cars that are at or beyond the crossing get sped up, which creates a gap in the middle for the pedestrian to cross. Meanwhile an observer down the road would only see a steady stream of traffic.

Most of the applications remain theoretical at this stage, though a proof of concept design using optical fibers has been constructed.