Jan 062012

For years physicists have been refining invisibility cloaks

For years physicists have been refining invisibility cloaks—physical setups that cleverly reroute light around a region in space, effectively concealing any object that might be inside. But now researchers at Cornell University have built the first temporal cloak, a device that obscures an object or event not at a particular point in space but at a specific moment in time.

In a preliminary demonstration, Cornell postdoctoral researcher Moti Fridman and his colleagues shone a laser beam through an experimental apparatus and into a detector. A physical object or even another beam of light in the laser beam’s path could create a change in the laser light that the detector would register. But with some clever optics, Fridman and his colleagues were able to open up a brief time gap in the beam and then close it back up as if the beam had gone undisturbed, and such that the detector did not register the interruption. The gap allows anything that would have otherwise affected the beam to instead slip right through [see animation below], leaving no trace for the detector to pick up.

The researchers used the cloak to obscure an optical pulse that ordinarily interacts with the laser beam to produce a telltale spike at a certain wavelength. When the event was cloaked, however, the telltale spike was basically undetectable.

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