Mathematicians find a way to hide waves inside an invisible 'hat'

Invisibility, once the subject of magic or legend, is slowly becoming reality. Over the past five years, mathematicians and other scientists have been working on devices that enable invisibility cloaks – perhaps not yet concealing Harry Potter, but at least shielding small objects from detection by microwaves or sound waves.

Research Would Allow Practical Applications of Cloaking

An international team of researchers, which includes Professor of Mathematics Allan Greenleaf from the University of Rochester, has come up with a process that would allow practical applications to be performed in a cloaked-or invisible-environment.

While cloaking might be advantageous for teenage wizards, it would have drawbacks in a science lab, the very place where cloaking would first be developed.

For example, a researcher needing to take precise sound pressure measurements inside a chamber faces two challenges. First, the very presence of a probe inside the chamber would subtly alter the acoustics of the environment, making accurate readings impossible. Second, if the probe could be perfectly cloaked, information on the outside would be unable to enter the cloaked environment, making it impossible to take any readings at all. The key would be to create a state of "approximate cloaking," which would hide the probe while letting in just enough sound waves that can be amplified in order for measurements to be taken.

The researchers have devised such a system, which they've dubbed "Schrödinger's hat," referring to the famed Schrödinger's cat in quantum mechanics. The name is also a nod to the ability to perform a task - or create something - with what appears to be nothing.

The findings have been published in the current Proceedings of the National Academy of Sciences.