Mathematicians Can Conjure MatterWaves Inside an Invisible Hat

[kullatiro]

 
ScienceDaily (May 29, 2012) —
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.


http://www.sciencedaily.com/releases/2012/05/120529182715.htm

[kullatiro]

ScienceDaily (May 25, 2012) — Many
people anticipating the creation of an
invisibility cloak might be surprised to
learn that a group of American
researchers has created 25,000
individual cloaks.

 But before you rush to buy one from
your local shop, the cloaks are just 30
micrometres in diameter and are laid
out together on a 25 millimetre gold
sheet.
This array of invisibility cloaks is the
first of its kind and has been created
by researchers from Towson
University and University of Maryland
who present their study on May 25, in
the Institute of Physics and German
Physical Society's New Journal of
Physics.
Although the well-reported intention
to make everyday objects disappear
with a Harry Potter-style cloak is
beyond this array of cloaks, they could
be used to slow down, or even stop,
light, creating what is known as a
"trapped rainbow."
The trapped rainbow could be utilised
in tiny biosensors to identify biological
materials based on the amount of
light they absorb and then
subsequently emit, which is known as
fluorescence spectroscopy. Slowed-
down light has a stronger interaction
with molecules than light travelling at
normal speeds, so it enables a more
detailed analysis.
Lead author of the study, Dr Vera
Smolyaninova, said: "The benefit of a
biochip array is that you have a large
number of small sensors, meaning
you can perform many tests at once.
For example, you could test for
multiple genetic conditions in a
person's DNA in just one go.
"In our array, light is stopped at the
boundary of each of the cloaks,
meaning we observe the trapped
rainbow at the edge of each cloak.
This means we could do
'spectroscopy on-a-chip' and examine
fluorescence at thousands of points
all in one go."
The 25 000 invisibility cloaks are
uniformly laid out on a gold sheet,
with each having a microlens that
bends light around itself, effectively
hiding an area in its middle. As the
light squeezes through the gaps
between each of the cloaks, the
different components of light, or
colours, are made to stop at ever
narrower points, creating the rainbow.
To construct the array of invisibility
cloaks, a commercially available
microlens array, containing all of the
individual microlenses, was coated
with a gold film. This was then placed,
gold-side down, onto a glass slide
which had also been coated with gold,
creating a double layer. A laser beam
was directed into the array to test
performance of the cloaks at different
angles.
The researchers believe that this type
of array could also be used to test the
performance of individual invisibility
cloaks, especially in instances where
they may be positioned close
together. In this study, for example,
the cloaks worked very well when light
was shone along the rows; however,
when it was shone at different angles,
imperfections were clearly visible.

http://www.sciencedaily.com/releases/2012/05/120525103920.htm