"Invisibility Cloak" Hides Information by Creating Holes in Time

Invisiblity cloaks have made headlines ever since Harry Potter first donned his. However, while a myriad of real-life attempts at the technology have surfaced in the last few years, researchers at Purdue University have demonstrated a method for “temporal cloaking” capable of making information vanish by creating holes in time.

The way it works, according to researchers, is through manipulating the phase, or timing, of light pulses. With the propagation of light similar to the waves of an ocean, when one wave going up interacts with another wave coming down, they cancel each out. Thus, by controlling the timing of these waves, scientists can make anything in the beam's path seem to disappear.

To do this, the scientists got their hands on and phase modulators commonly found in optical communications where they are used to modify signals. Then, by using two to first create the holes and then two more to cover them up, the scientists were able to create the appearance that nothing was done to the initial signal in the first place.

For this reason, the work is different to other "invisibility cloaks" in that it hides events in time, rather than spatial objects.

And while a study published in early 2012 employed similar technology, the method it expounded only effectively cloaked a tiny fraction – about a 10,000th of a percent – of events. However, in the new study Purdue researchers showed that they have increased that to about 46 percent of the time.

With numbers that high, the scientists are beginning to talk about commercial application.

"More work has to be done before this approach finds practical application, but it does use technology that could integrate smoothly into the existing telecommunications infrastructure," said Purdue University graduate student Joseph Lukens, working with Andrew Weiner, the Scifres Family Distinguished Professor of Electrical and Computer Engineering.

Among the uses envisioned by the scientists are those that apply to the military, homeland security or law enforcement.

"It might be used to prevent communication between people, to corrupt their communication links without them knowing," Lukens said. "And you can turn it on and off, so if they suspected something strange was going on you could return it to normal communication."

Published in the journal Nature, the study was funded in part by the National Science Foundation and the U.S. Naval Posgraduate School under the National Security Science and Engineering Faculty Fellowship Program. Other financial support came from the U.S. Department of Defense.

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