Scientists have re-investigated a sixty-year-old idea by the American
physicist P.W. Anderson and provided new insights into the quantum world.
Quantum physics explains how the world’s building blocks such as atoms or
electrons are put together. Everything we see around us is made up of atoms
and electrons which are so small one billion atoms placed side by side could
fit within a centimeter.
Because of the way atoms and electrons behave, scientists describe this
behavior as waves. In the research, scientists looked at how waves can go
through a landscape containing obstacles placed in random positions.
Anderson initially developed this idea to describe electrons in
semiconductors. His insight greatly contributed to the development of
computer chips and electronics.
“His work describes a common phenomenon that happens for all kinds of waves,
be it light waves, ocean waves, sound waves or quantum-mechanical waves,”
says lead researcher Maarten Hoogerland from the University of Auckland.
Waves, unlike particles that travel in straight lines, can go around
obstacles, but if there are enough random obstacles, the waves cannot get
through because they interfere with each other and cancel themselves out.
In the Quantum Information Lab at the University, researchers took
Anderson’s work one step further and added an ultra-cold atom experiment to
the mix. With the aid of high tech lasers, they manipulated these ultra-cold
atoms until they were so cold, their wave behavior became visible to the
eye.
“We are talking a billionth of a degree above absolute zero (-273.15 degrees
C) so that is pretty chilly. We have created customized patterns of
obstacles to stop the waves, and when we take a picture, we can find out
where these atoms are,” Dr Hoogerland says.
“This way, we can see what exactly is required to get our quantum-mechanical
waves to reflect off obstacles, and why the waves do not get in.”
Working together, through the Dodd-Walls Centre for Photonics and Quantum
Technologies, with researchers at the University of Otago, the research team
was able to match the results of the experiments with theoretical
predictions, giving way to new insights which could be used to create and
test “designer materials” with customized properties.
Reference:
“Observation of two-dimensional Anderson localisation of ultracold atoms” by
Donald H. White, Thomas A. Haase, Dylan J. Brown, Maarten D. Hoogerland,
Mojdeh S. Najafabadi, John L. Helm, Christopher Gies, Daniel Schumayer and
David A. W. Hutchinson, 2 October 2020, Nature Communications.
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