But even that has potential uses, Valentine said. In optical computing, for example, such cloaks could be used to allow light to move more efficiently, by hiding the parts of a computer chip that get in the way of the beams.
Also, expensive dielectric mirrors—special mirrors used to make printed circuits for electronics—can be ruined by tiny defects in their surfaces.
"You could cloak a defect and make it look like a perfect mirror again," Valentine said.
Scaling up to hide an object the size of a BB-gun pellet might be possible, but going larger will be difficult, he said.
In the Berkeley material, for instance, "the holes have to be smaller than the wavelength of light, and many are required."
From Theory to Practice
The development of these working invisibility cloaks is exciting, but it's not a huge theoretical breakthrough, Ulf Leonhardt, a theoretical physicist at Scotland's University of St. Andrews, said in an email.
"Such an idea already appeared in my very first paper on cloaking," published in the journal Science in 2006, he said.
Carl Poitras, a researcher with the Cornell group, agrees.
"Like a lot of things we can do," he said, "the theory is predicted ahead of time, but the technology isn't there to show it."
Now, for cloaking devices at least, the theoretical models are starting to become real-life products.
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