By adding some magnetic sensation to an exotic quantum experiment, physicists have produced an ultra-stable one-dimensional quantum gas with never-before-seen ‘scar’ conditions – a feature that may one day be useful in securing quantum information.
As the story goes, the Greek mathematician and thinker Archimedes came across an invention while traveling through ancient Egypt that would later bear his name. It was a machine consisting of a screw housed in a hollow tube that trapped water and pulled at rotation. Now researchers led by Stanford University physicist Benjamin Lev have developed a quantum version of Archimedes’ propeller that, instead of water, transports fragile collections of gas atoms to higher and higher energy states without collapsing. Their discovery is set out in an article published today (January 14, 2021) in Science.
Experimental physicists have created a unique, one-dimensional quantum gas system that remains extremely stable while being pumped to higher energy conditions. The researchers compare it to water transported by an Archimedes propeller.
“My expectation for our system was that the stability of the gas would change just a little bit,” Lev said. He is an associate professor of applied physics and physics at the School of Humanities at Stanford. “I did not expect to see a dramatic, complete stabilization of it. It was beyond my wildest perception. ”
Along the way, the researchers also observed the development of scarring conditions – extremely rare particle orbits in an otherwise chaotic quantum system in which the particles repeatedly trace back their steps like spores overlapping in the forest. Scars are of particular importance because they can provide a protected refuge for information encoded in a quantum system. The existence of scarring conditions within a quantum system with many interaction particles – known as a quantum multi-body system – has only recently been confirmed. The Stanford experiment is the first example of the scar condition in a multitude of bodily quantum gases and only the second observation of the phenomenon in the real world.
Super and stable
Lev specializes in experiments that we understand how different parts of a quantum-many-body system settle in the same temperature or thermal equilibrium. This is an exciting area of research, as resisting this so-called ‘thermization’ is the key to creating stable quantum systems that can drive new technologies, such as quantum computers.
In this experiment, the team investigated what would happen if they adapted a very unusual experimental system with a lot of body, called a super Tonks-Girardeau gas. These are highly excited one-dimensional quantum gases – atoms in a gaseous state confined to a single line of motion – set up in such a way that their atoms develop extremely strong attractive forces for each other. What’s there? super about them is that, even under extreme forces, they should theoretically not plunge into a ball-like mass (as normal attractive gases would do). In practice, however, it collapses due to experimental imperfections. Lev, who has a penchant for the strong magnetic element dysprosium, wondered what would happen if he and his students created a super Tonks-Girardeau gas with dysprosium atoms and changed their magnetic orientations. Maybe they would collapse a little better than the non-magnetic gases?
‘The magnetic interactions we were able to add were very weak compared to the attractive interactions already occurring in the gas. So our expectations were that not much would change. “We thought it would still collapse, just not that easily,” Lev said. Stanford Ginzton Lab and Q-FARMING. “Wow, we were wrong.”
Their dysprosium variation eventually produced a super Tonks-Girardeau gas that remained stable no matter what. The researchers flipped the atomic gas between the attractive and repulsive states and elevated or “screwed” the system to higher and higher energy states, but the atoms still did not collapse.
Build from the foundation
Although there are no immediate practical applications of their discovery, the Lev Laboratory and their colleagues are developing the science needed to propel the much-anticipated quantum technology revolution. For now, Lev said, the physics of quantum-many-body systems out of equilibrium remains surprising throughout.
“There is still no textbook on the shelf that you can pull out to tell you how to build your own quantum factory,” he said. “If you compare quantum science to where we were when we discovered what we needed to know to build chemical plants, then say, it’s like we’re doing the late 19th century job now.”
These researchers first began by examining the many questions about their quantum Archimedes’ screw, including how to describe these scars mathematically and whether the system becomes thermal – which it should eventually do – how it works. More immediately, they plan to measure the momentum of the atoms in the scar states to develop a thorough theory about why their system behaves the way it does.
The results of this experiment were so unpredictable that Lev says he can not strongly predict what new knowledge will come from deeper examination of the quantum of Archimedes’ screw. But this is perhaps experimental at best.
‘This is one of the few times in my life where I actually worked on an experiment that was really experimental and not a proof of the existing theory. “I did not know in advance what the answer would be,” Lev said. “Then we found something that was really new and unexpected and that made me say, ‘Yay experimental! ”
Reference: “Topological pumping of a 1D dipolar gas in strongly correlated preterm conditions” by Wil Kao, Kuan-Yu Li, Kuan-Yu Lin, Sarang Gopalakrishnan and Benjamin L. Lev, January 14, 2021, Science.
DOI: 10.1126 / science.abb4928
Additional writers from Stanford are graduate students Wil Kao (co-author), Kuan-Yu Li (co-author) and Kuan-Yu Lin. A professor of CUNY College of Staten Island and CUNY, New York, is also co-author. Lev is also a member of Stanford Bio-X.
This research was funded by the National Science Foundation, the Air Force Office of Scientific Research, the Natural Science and Engineering Research Council of Canada, and the Olympiad Scholarship of the Taiwanese Ministry of Education.