Space-Time Cloaking

It sounds like a concept straight out of science fiction.

But one day a ‘spacetime cloak’ could make it possible to ‘hide’ history by editing out passages of time.

The device would speed up and slow down light to give the illusion that events have not happened.

A ‘cloaked’ individual could, for instance, travel from one place to another while appearing to vanish and rematerialise instantaneously in a new location.

A scientifically-savvy thief with access to the technology could open a safe, empty its contents, and make his escape right under the watchful eye of a surveillance camera.

The video footage would show that the safe door was closed all the time. In effect, events in history could be ‘edited out’ so that they never appear to have happened.

It sounds like the stuff of fantasy, but scientists at Imperial College London have proved it could work in theory by adapting standard fibre-optic technology.

As well as being a safe-cracker’s dream, they believe the idea has a wealth of more practical applications in the realms of data processing and computing.

The research is outlined today in the Institute of Physics publication Journal of Optics.

Lead scientist Professor Martin McCall said: ‘We have shown that by manipulating the way the light illuminating an event reaches the viewer, it is possible to hide the passage of time.

‘If you had someone moving along the corridor, it would appear to a distant observer as if they had relocated instantaneously, creating the illusion of a Star Trek transporter. So, theoretically, this person might be able to do something and you wouldn’t notice.’

In previous experiments scientists have shown that light can be curled around objects to make them seem invisible.

The physics is perhaps most easily explained by thinking of the particles of light as cars on a busy road.


A graphic to explain how the cloaking procedure would work. The light rays would be sped up and slowed down to allow a gap between them to open up
quantum cloak

quantum cloak

Researcher Alberto Favaro said: ‘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.’

Applied to light, the period in which the pedestrian crosses the road would create a moment in which someone could move or carry out a deed undetected.

The ‘invisibility cloak’ technology employs so-called ‘metamaterials’ whose structure allows light rays to be bent or even reversed.

The new research goes a step further by devising a way to conceal events as well as objects.

This is achieved not by bending light, but by manipulating the speed at which light travels through a material medium.

Illuminating light is divided up into an accelerated ‘leading part’ which arrives before an event, and a slowed ‘trailing half’ which lags behind and arrives after the event.

Both the fast and slow rays are joined back together and adjusted to the same speed before being seen by an observer. The result is a concealed passage of time or ‘temporal void’ during which the event is not illuminated and goes unnoticed.

Star Trek fans should also note that the technology only creates the illusion of teletransportationn, with the traveller still having to put in the physical effort to move from A to B.

Graduate student Alberto Favaro, who also worked on the project, said: ‘It is unlike ordinary cloaking devices because it does not attempt to divert light around an object.

‘Instead it pulls apart the light rays in time, as if opening a theatre curtain – creating a temporary corridor through which energy, information and matter can be manipulated or transported undetected.’

Although a spacetime cloaking device may still be far in the future, the scientists have already come up with a proof-in-principle design based on customised fibreoptics that lends itself to computing applications.

Potentially it could make real the strange concept of ‘interrupt-without-interrupt’ signal processing.

During the cloaking operation, processing on a given data channel could be interrupted to divert resources to a priority calculation on a parallel channel.

Yet it would look as if no interruption had taken place, and the original channel had processed the information continuously.

via: dailymail

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