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.