Chinese scientists’ quantum study hailed as a ‘breakthrough of the year’
Physics World puts creation of the world’s first ultracold three-atom molecules in top 10 scientific achievements of the year The accolade comes days after the researchers unveiled their latest findings, expected to shed new light on how chemicals behave at the quantum level By Ling Xin in Beijing Published: 6:00pm, 8 Dec, 2022 https://www.scmp.com/news/china/science/article/3202526/chinese-scientists-quantum-study-hailed-breakthrough-year?module=live&pgtype=homepage Chinese scientists are ending the year with a double celebration. Days after releasing details of their latest breakthrough, a team from Anhui in eastern China has been included in Physics World’s top 10 achievements of 2022. The researchers, from the University of Science and Technology of China (USTC), were recognised for their initial study earlier this year, which outlined indirect evidence that they had created the first ultracold three-atom molecules. In their latest paper, published last Friday by the journal Science, the team confirmed the breakthrough which is expected to shed new light on how chemicals behave at the quantum level. And on Tuesday, the Institute of Physics’s membership journal listed their first study – published in the February edition of Nature – as one of its top 10 scientific breakthroughs of the year. In their most recent study, the USTC researchers produced around 4,000 gas molecules, each containing one sodium-23 atom and two potassium-40 atoms, at 100 nanokelvins – less than one millionth of a degree above absolute zero. The achievement could help simulate chemical reactions, design new materials and even lead to a better understanding of the notoriously complex three-body problem. “In the past two decades, researchers have used two atoms to make ultracold molecules. Our work took that to three, which is a first step towards assembling poly-atomic ultracold molecules,” said the paper’s co-author Zhao Bo, from the University of Science and Technology of China (USTC) in Hefei, Anhui province. The paper’s reviewers hailed the study as a “milestone” in ultracold chemistry, a field in which atoms and molecules are cooled to extremely low temperatures to observe how they behave in slow motion, as well as how chemical reactions occur at the quantum level. “Complex physics systems, including most chemical reactions, are very difficult to calculate even with the most powerful computers. Since ultracold atoms and molecules are highly controllable, we can use them to create an ideal complex system and study how it works,” Zhao said. Zhao explained that by precisely measuring the structure, energy levels and other properties of three-atom molecules, researchers hope to provide observational evidence for the modelling and theoretical interpretations of the three-body problem in the quantum world. The three-body problem seeks to establish the subsequent motion of three masses from their initial positions and velocities, according to Newton’s laws of motion and universal gravitation. The first example of the problem to receive extended study was in astronomy and involved the Earth, moon and sun. No general solution to the problem is believed to be possible, because the motion of more than two bodies quickly becomes chaotic, a situation which is even more complex at the quantum level. While scientists have long been able to chill atoms with lasers to within billionths of a degree above absolute zero, cooling molecules in the same way is much more challenging. As light particles from a laser beam are absorbed and then re-emitted by atoms, they lose some kinetic energy and cool down. However, molecules are less responsive to laser beams because they are heavier. They also need to have the right internal structure to trigger the absorption and re-emission process. One solution is to use ultracold atoms as building blocks to assemble ultracold molecules, by generating a phenomenon known as the Feshbach resonance, which causes two slowly colliding atoms to stick together into an unstable and short-lived compound. This approach was used by a US team in 2003 to pair potassium atoms and create the world’s first ultracold diatomic molecules at about 150 nanokelvins above absolute zero. In 2019, Zhao and his colleagues at USTC were using the method to produce two-atom molecules when they observed Feshbach resonances between atoms and molecules – instead of just atoms. “Since then, we’ve been thinking about using them as components to build triple-atom molecules,” Zhao said. Finally, this year the researchers had indirect evidence that they had succeeded in forming triatomic structures. But the molecules were short-lived and hard to confirm. For their latest study, the researchers switched to a different method, applying a fine-tuned magnetic field to help trigger Feshbach resonances between ultracold potassium-40 atoms and molecules made up of sodium-23 and potassium-40. The results provided the first clear evidence of the production of ultracold three-atom molecules, their paper said. “We explored different techniques to make this work, since we didn’t understand how the resonances work between atoms and molecules, and we didn’t even know how to theoretically describe such three-atom molecules,” Zhao said. The team will now work to bring the weak and unstable molecules into a more stable state. Zhao said that in the longer term – once they have a better understanding and control of the process – they might take it a step further and try to make four-atom ultracold molecules. _______________________________________________ Link mailing list [email protected] https://mailman.anu.edu.au/mailman/listinfo/link
