Quantum mechanics – the behavior of the Universe at the smallest of scales – continues to surprise us, with scientists now having been able to successfully create a new kind of quantum object at will in the laboratory: “domain walls.”
The discovery can help researchers better understand exotic quantum particles—and could suggest avenues for new technology in the future, such as quantum electronics or quantum memory.
Published on February 2, 2022, in the journal Nature, the research was conducted in Prof. Cheng Chin’s lab, which studies novel quantum systems and the physics that underlie them.
In one of their experiments, the UChicago scientists noticed an intriguing occurrence in atoms at extremely low temperatures. Under the right conditions, groups of atoms can segregate into domains, and a “wall” forms at the junction where they met. This domain wall behaved like an independent quantum object.
“It’s kind of like a sand dune in the desert – it’s made up of sand, but the dune acts like an object that behaves differently from individual grains of sand,” says physicist Kai-Xuan Yao from the University of Chicago.
There has been previous research into domain walls, but they’ve never been able to be created at will in the laboratory until now, giving scientists the ability to analyze them in new ways. It turns out they act as independent quantum objects, but not necessarily in the way that scientists would expect them to.
That unexpected behavior means domain walls join a class of objects called emergent phenomena, where particles that join together seem to follow a different set of physics laws than particles that are operating on their own.
One of the unusual observations made by the team is the way that domain walls react to electric fields, something which will need further study to untangle. For now, just being able to produce and manipulate these walls is an important step forward.
“We have a lot of experience in controlling atoms,” says physicist Cheng Chin from the University of Chicago. “We know if you push atoms to the right, they will move right. But here, if you push the domain wall to the right, it moves left.”
Part of the reason why the discovery is so important is that it could teach us more about how atoms behaved at the very beginning of the Universe’s existence: Particles that were once clumped together eventually expanded to form stars and planets, and scientists would like to know exactly how that happened.
This domain wall discovery falls under the umbrella of what’s known as dynamical gauge theory – a way to test and compute the dynamics of quantum phenomena in the lab. These discoveries could explain how emergent phenomena operate in everything from materials to the early Universe.
As well as looking backwards though, the researchers are also looking forwards. Once more is understood about how domain walls can be controlled, it could open up opportunities for new quantum technologies.
“There may be applications for this phenomenon in terms of making programmable quantum material or quantum information processors,” says Chin.
“It can be used to create a more robust way to store quantum information or enable new functions in materials. But before we can find that out, the first step is to understand how to control them.”
Source:
“Domain-wall dynamics in Bose–Einstein condensates with synthetic gauge fields” by Kai-Xuan Yao, Zhendong Zhang & Cheng Chin, 2 February 2022, Nature.