Nov 8 2017
Scientists are not generally treated to fireworks when they learn something about the universe. However, a team of University of Chicago researchers discovered a show waiting for them at the atomic level — along with a undiscovered form of quantum behavior.
Jets of atoms shoot off together like fireworks from a central disc in a new quantum phenomenon discovered by UChicago scientists (color added for illustration). Courtesy of Cheng et al.
“This is a very fundamental behavior that we have never seen before; it was a great surprise to us,” said study author and professor of physics Cheng Chin. Published Nov. 6 in Nature, the research presents an unusual phenomenon — seen in what was believed to be a much-understood system — that may at some point be useful in quantum technology applications.
Chin’s lab analyzes what happens to particles known as bosons in a special state referred to as a Bose-Einstein condensate. Bosons, when cooled down to temperatures near absolute zero, will all condense into the same quantum state. Researchers used a magnetic field, pushing the atoms, and they then started to collide — some of which were sent flying out of the condensate. However, instead of a uniform field of random ejections, they observed bright jets of atoms shooting together from the rim of the disk, similar to miniature fireworks.
“If you’d asked almost anyone to predict what would happen, they would have said that these collisions would just send atoms flying off in random directions,” said postdoctoral fellow Logan Clark, the first author of the study; he and a co-author, postdoctoral fellow Anita Gaj, were the first to observe the phenomenon. “But what we see instead are thousands of bosons bunching together to leave in the same direction.”
“It’s like people forming a consensus and leaving in groups,” Chin said.
The small jets may show up in other systems, researchers stated — and understanding them may help throw light on the fundamental physics of other quantum systems.
Furthermore, the jets, like several other new quantum behaviors, may be of importance in technology.
“For example, if you sent a particular atom in one direction, then a bunch more would follow in that same direction, which would help you amplify small signals in the microscopic world,”
Logan Clark, postdoctoral fellow, University of Chicago and first author of the study,
Since there is energy delivered to the system and the particles are not at their ground states, it indeed falls under the category of a principally hot area of quantum engineering research known as “driven” quantum systems, the authors said. The physics of systems in these quantum states is yet to be completely understood, but vital for engineering useful technologies.
However, Bose-Einstein condensates are generally considered to be a well-studied area, hence they were excited to witness a never-before-documented behavior, the scientists said.
“If you see something crazy in this simple experiment, it makes you wonder what else is out there,” said graduate student Lei Feng, also a co-author.