Tuesday, December 23, 2014

Time cloak can hide messages in laser light

From the New Scientist comes this report of a device that can conceal events and not just objects.  Termed “Time Cloak,” it can hide secret messages through a trick of light, making information invisible to all but the intended recipient.
Like an invisibility cloak that makes something disappear in plain sight, a time cloak could conceivably make an event disappear in time. It works by manipulating light traveling along an optical fibre.
The device might still be a long way before finding applications in hiding, say some crime, as the New Scientist article conjectured.    Joseph Lukens, an electrical engineer at Purdue University in the USA gives some current applicability:
"With this new device, we don't just limit ourselves to thinking about cloaks as a way of preventing somebody from getting information, but also as a way to enable communication.” 
Lukens and his colleagues created two different communications channels using lasers tuned to two different frequencies. One is a regular frequency and the other is a time-cloaked channel that remains hidden unless you know it's there. Photons from each laser traveled along the same fibre, but only the intended recipient, who just needs to tune in to the right channel, gets to see the secret information. According to Lukens, “One guy sees nothing, the other guy sees everything."
         Not only could the cloak deliver the messages, it also successfully fended off outside attempts to scramble the information. A similar device could one day improve current communication systems, says Moti Fridman at Bar-Ilan University in Israel.
"As we get closer and closer to the limits of current data transfer systems, we need to consider creative ideas for increasing the bandwidth in current systems with minimal changes," says Fridman. "This is a beautiful example for using cloaking."

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