New ‘invisibility cloak’ creates holes in time
By Tia Ghose
Published June 06, 2013
LiveScience
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The magic of science means Harry Potter’s “invisibility cloak” is an impending reality. (Warner Brothers)
The researchers, who describe their work June 5 in the journal Nature, found that by tweaking the optical signals in telecommunications fibers, they created a way to essentially mask data sent between a sender and a receiver to outside observers. This isn’t the first time researchers have taken a page from Harry Potter: Last year, scientists also demonstrated a similar invisibility cloak.
But the new “time cloak” can create many time holes in rapid succession, which means masked data could be sent at commercial data speeds, said Martin McCall, a theoretical-optics researcher at Imperial College London who was not involved in the study.
‘Imagine that some cars at the front of the stream speed up and ones behind slow down, so a gap can open up.’
– Martin McCall, a theoretical-optics researcher at Imperial College London
Time cloak
In 2006, McCall proposed the idea of making optical data (information sent through optical fibers) invisible to an outsider by manipulating the light that transmits that data.
The process involves manipulating the flow of photons, or particles of light, in an optical data stream.
“If you consider light as a flow of particles a bit like cars going down a highway, you can imagine that some of the cars at the front of the stream speed up and ones behind slow down so a gap can open up,” McCall said.
If data are sent within that gap in time, when the photons eventually change speed to close up the gap, it appears to an outside observer as though nothing ever happened.
Last year, Cornell University researcher Alexander Gaeta and his colleagues demonstrated that a time cloak was possible. But that method was able to create short, 12-picosecond time cloaks that were separated by 24 microseconds meaning a user would have to wait a million times the length of the gap to send any more hidden data
. That was much too slow for commercial applications.
Commercial cloak
To attempt to speed up the process, Joseph Lukens, an electrical engineering doctoral candidate at Purdue University, and his colleagues began developing a time cloak that used existing commercial equipment and could transmit optical data at high speeds.
They also employed the principle that light is both a particle and a wave at the same time. In their method, they created a pattern in the traveling light beam so that the wave’s peaks were focused on smaller and smaller areas, and the troughs, or dark spots, got bigger and bigger. This time-lensing effect created several spots in time and space where there was zero light, Lukens said.
“By doing this type of interference effect, we focus the light to even smaller points in time,” Lukens told LiveScience. “So, in the middle, we have all of our energy focused on very small points, and between them, we have regions where, if something were to happen, it would not be detected because there’s no light there to pick it up.”
At the end of the path, the researchers would undo the operations so that to an outside observer, it would seem as though the holes never existed.
The new method covers 46 percent of the spots in a cable, through which the optical data runs, with time holes that can be repeated at 12.7 gigabits per second a speed used in commercial applications.
The new technique could one day be used to create ultrasecure Internet communications, or to foil communications between criminals such as terrorists. On a more mundane level, it could be used to avoid data traffic jams at connection points in networks, Lukens said.
The findings are a significant advance, McCall said.
“It does make it possible to do these things at telecommunication data rates,” McCall told LiveScience. “And as we all know, once the tabletop demonstration has been shown, it’s then a matter of technology the miniaturization, the efficient system engineering tend to follow.”
Michael Bradley - Time Traveler 