A matter wave hitting a Schrödinger’s hat. The wave inside the container is magnified. Outside, the waves wrap as if they had never encountered any obstacle. G. Uhlmann, U. of Washington

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.

A
University of Washington mathematician is part of an international team
working to understand invisibility and extend its possible
applications. The group has now devised an amplifier that can boost
light, sound or other waves while hiding them inside an invisible
container.

“You
can isolate and magnify what you want to see, and make the rest
invisible,” said corresponding author Gunther Uhlmann, a UW mathematics
professor. “You can amplify the waves tremendously. And although the
wave has been magnified a lot, you still cannot see what is happening
inside the container.”

The findings are published online this week in the Proceedings of the National Academy of Sciences.

As
a first application, the researchers propose manipulating matter waves,
which are the mathematical description of particles in quantum
mechanics. The researchers envision building a quantum microscope that
could capture quantum waves, the waves of the nanoworld. A quantum
microscope could, for example, be used to monitor electronic processes
on computer chips.

The
authors dubbed their system “Schrödinger’s hat,” referring to the famed
Schrödinger’s cat in quantum mechanics. The name is also a nod to the
ability to create something from what appears to be nothing.

“In
some sense you are doing something magical, because it looks like a
particle is being created. It’s like pulling something out of your hat,”
Uhlmann said.

Matter waves inside the hat can also be shrunk, though Uhlmann notes that concealing very small objects “is not so interesting.”

Uhlmann,
who is on leave at the University of California, Irvine, has been
working on invisibility with fellow mathematicians Allan Greenleaf at
the University of Rochester, Yaroslav Kurylev at University College
London in the U.K., and Matti Lassas at the University of Helsinki in
Finland, all of whom are co-authors on the new paper.

The
team helped develop the original mathematics to formulate cloaks, which
must be realized using a class of engineered materials, dubbed
metamaterials, that bend waves so that it appears as if there was no
object in their path. The international team in 2007 devised wormholes
in which waves disappear in one place and pop up somewhere else.

For
this paper, they teamed up with co-author Ulf Leonhardt, a physicist at
the University of St. Andrews in Scotland and author on one of the
first papers on invisibility.

Recent progress suggests that a Schrodinger’s hat could, in fact, be built for some types of waves.

“From
the experimental point of view, I think the most exciting thing is how
easy it seems to be to build materials for acoustic cloaking,” Uhlmann
said. Wavelengths for microwave, sound and quantum matter waves are
longer than light or electromagnetic waves, making it easier to build
the materials to cloak objects from observation using these phenomena.

“We
hope that it’s feasible, but in science you don’t know until you do
it,” Uhlmann said. Now that the paper is published, they hope to find
collaborators to build a prototype.

The
research was funded by the National Science Foundation in the U.S., the
Engineering and Physical Sciences Research Council and the Royal
Society in the U.K., and the Academy of Finland.

Source: University of Washington