Posted in | Quantum Physics

Scientists Explore How Quantum Knots Tie and Untie Themselves

Researchers have shown that it is possible to tie quantum gas into knots using magnetic fields. The collaborative research team from Aalto University and Amherst College, USA, were the first to produce these knots, and they have currently explored how the knots act over time. The astonishing result is that the knots untie themselves after a span of time, before changing into a vortex.

Particle densities related to the decay of the quantum knot (left), which surprised researchers by untying itself after a few microseconds and eventually turning into the spin vortex (right). (Image credit: Tuomas Ollikainen/Aalto University)

The study was mostly performed by Tuomas Ollikainen, a PhD student at Aalto University who divided his time between conducting experimental work in Amherst in Massachusetts, and examining the data and pursuing his theories at Aalto.

We hadn’t been able to study the dynamics of these sorts of three-dimensional structures experimentally before, so this is the first step to this direction. The fact that the knot decays is surprising, since topological structures like quantum knots are typically exceptionally stable. It’s also exciting for the field because our observation that a three-dimensional quantum defect decays into a one-dimensional defect hasn’t been seen before in these quantum gas systems.

Tuomas Ollikainen, PhD Student, Aalto University

Controlling quantum gasses

The scientists are expectant their new study will pave new paths in experimental research. One of the major breakthroughs in the research was being able to have proper control over the state of the quantum gas, which enabled them to detect variations in its structure, like the deterioration of the knots and the development of the vortex.

Of course one can simulate these things but actually making quantum knots is not that easy. By being able to control the environment better we can explore different effects and get to understand more about these exciting quantum systems.

Tuomas Ollikainen, PhD Student, Aalto University

“When we tied quantum knots in 2016, it was the first realization of three-dimensionally winding topological structures. That was like breathing air another planet for the first time. Amazing.” says Prof. Mikko Möttönen, head of Quantum Computing and Devices group where Ollikainen works.

“I know that many researchers have paid attention to our work and got inspiration to try this out in completely different type of systems. It would be great to see this technology being used some day in a practical application, which may well happen. Our latest results show that while quantum knots in atomic gases are exciting, you need to be quick to use them before they untie themselves. Thus the first applications are likely to be found in other systems.” Möttönen continues.

The Quantum Computing and Devices group is a part of QTF, the Academy of Finland Centre of Excellence for Quantum Technology. The study profited from the computational resources from CSC–IT Center for Science Ltd. and Aalto Science-IT project.

Source: https://www.aalto.fi/en

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