Invisibility cloaks could someday be a reality

Researchers at Cornell University’s School of Applied and Engineering Physics have achieved the first experimental demonstration that something can be made invisible through a technique called temporal cloaking. Physicists have been grappling with ways to create invisibility cloaks for some time now. Theoretically, an object can be made invisible by distorting the electromagnetic field as it flows around the object and returning the electromagnetic field back to its original condition prior to the field being observed. The object remains invisible to an observer who cannot detect that a distortion in the electromagnetic field ever took place.

Invisibility cloaks have been created in the past by bending light around an object through a technique called spatial cloaking. Now, Moti Fridman and his colleagues at Cornell University have demonstrated that objects can also be cloaked by changing the speed of light as it passes by an object.

The researchers performed the temporal cloaking feat by manipulating the speed of light as it traveled through a fiber-optic cable. The cloaking device consisted of two consecutive dispersion lenses that first accelerated the light beam then, slowed it down. In between the two lenses, the researchers bombarded the light with energy to alter its wavelength. When the cloaking device was turned off, the altered wavelengths were clearly observable to the researchers. However, when the cloaking device was turned on, the researchers were unable to detect that a disruptive event had occurred. In essence, the event was hidden in a “time hole.”

The temporal gap created by the cloaking device lasted only 110 nanoseconds. Researchers estimate that their device could be modified to hide events up to a maximum of 1.25 microseconds – about 1 millionth of a second. The short time frames involved limit the applicability of what types of events can be hidden, so don’t start fantasizing about what sort of wizardly things you may be able to do with this technology in the near future.

Martin McCall, professor at the Imperial College of London, and his colleagues were among the first to propose the use of temporal cloaking to hide events. They proposed the idea in the February 2011 issue of the Journal of Optics. McCall estimates that cloaking an event for eight minutes would require a device the size of the solar system. Cloaking events on time scales of less than a second could, however, be useful in the fields of signal processing and computing technology.

The results describing the first experimental demonstration of temporal invisibility cloaking by Fridman and others at Cornell University’s School of Applied and Engineering Physics are still preliminary and have not yet been published in a peer-reviewed journal.