Event-hiding "temporal cloak" demonstrated


October 13, 2011

Cornell researchers have demonstrated a working temporal cloak that creates a gap in the flow of light to conceal events (Image: fdecomite via Flickr)

Cornell researchers have demonstrated a working temporal cloak that creates a gap in the flow of light to conceal events (Image: fdecomite via Flickr)

Last year researchers at Imperial College London proposed that along with being used to cloak physical objects metamaterials could also be used to cloak a singular event in time. A year later, researchers from Cornell University have demonstrated a working "temporal cloak" that is able to conceal a burst of light as if it had never occurred.

In a research paper published in the Journal of Optics last year, Prof. Martin McCall and his team at Imperial College London said it should be theoretically possible to create a "Spacetime Cloak" by using metamaterials - a class of artificial materials engineered to have properties not be found in nature - to speed up the leading edge of light waves, while slowing down the trailing half. This would create a "corridor" between the two halves, at which point their source wouldn't be observable.

To demonstrate the theory, a Cornell research team led by Moti Fridman sent a beam of light down an optical fiber and passed it through a split-time lens - a silicon device originally designed to speed up data transfer. As the beam passes through the first lens it is compressed, leaving a dead zone or gap in the flow of light. A similar lens further along the path reverses the velocity adjustments, decompressing the light wave so it appears that the light coming through the second lens is uninterrupted as if no distortion had occurred.

To test the temporal cloak's performance the researchers created pulses of light directly between the two lenses that repeated like clockwork at a rate of 41 kHz. When the cloak was off, the researchers were able to detect a steady beat, but after switching on the cloak, which was synchronized with the light pulses, it appeared as if the pulses were erased from the data stream.

Rather than relying on the properties of metamaterials as was initially proposed by McCall, the temporal cloak demonstrated by the Cornell research team relies on the fundamental properties of light and how it behaves under highly constrained space and time conditions.

The length of the cloaked area is a mere six millimeters (0.2 in) long and the effect can only lasts for 110 nanoseconds. The team says the best it can achieve will be 120 microseconds because longer durations would create turbulence in the system that would hint that an event had occurred. To achieve any measurable macroscopic effects would require an experiment on planetary or even interplanetary scales, the researchers say.

The Cornell team will present their findings in a presentation "Demonstration of Temporal Cloaking" at the Optical Society's Annual Meeting, Frontiers in Optics (FiO) 2011, being held in San Jose, California, next week.

About the Author
Darren Quick Darren's love of technology started in primary school with a Nintendo Game & Watch Donkey Kong (still functioning) and a Commodore VIC 20 computer (not still functioning). In high school he upgraded to a 286 PC, and he's been following Moore's law ever since. This love of technology continued through a number of university courses and crappy jobs until 2008, when his interests found a home at Gizmag. All articles by Darren Quick

Wow..cloaking Space-time events...invisibility cloaks.. succesful animal brain transplants..instilling life to inorganic matter.. reversing cellular aging.. and letsnot forget the handheld \'communicators\' or \'globals\' a la \'Earth Final Conflict\' (smartphones) This story is just another in a long line that clearly shows we\'re stepping into \'Star Trek\' territory indeed.. Some theme music if you please...


One of the biggest problems in pop science reporting has to be trying to translate the screwy idioms that are so popular with scientists. \"Cloak a singular event in time\" sounds like they\'re doing something naughty with relativity, when in fact it seems they are just messing around with light frequencies- and on a very insignificant scale.

Duane Phillips

\"researchers from Cornell University have demonstrated a working \"temporal cloak\" that is able to conceal a burst of light as if it had never occurred.\"

And if I cover my eyes, it\'s as if nothing happens anywhere!?

Stephen Dunn

I have a feeling that this might someday play an interesting role in light-wave data encryption.


On interplanetary scales, I suggest hiding behind a nearby moon whenever you need to have a talk with your secret friends. It will be much easier, and no one will ever find out.


Great! Humans go one better - with lying! LOL

Mik Os

Cornell University wins in my book.

Mike Nielsen
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