quantum knots
January 19, 2016

Researchers observe ‘quantum knots’ for the first time ever

Quantum matter is essentially the smallest form of matter and researchers at Aalto University in Finland have just reported the first-ever observations of "quantum knots".

For many years, physicists have been theorizing it should be possible for knots to form in quantum fields, but scientists haven't been able to actually see one. According to a report in the journal Nature Physics, Finnish scientists developed knotted solitary waves, or knot solitons, in the quantum-mechanical field.

The quantum-mechanical field in which the knots were formed divides into an infinite amount of interconnected rings, each with its own field direction. The generated structure is topologically steady as it can't be divided without breaking the rings. Put simply, one won't be able to untie the knot unless the state of the quantum matter is destroyed.

In the study, physicists subjected a condensate to rapid transformations of an expressly-designed magnetic field, tying the knot in under a thousandth of a second. After that initial success, the team has been able to successfully repeat their results several hundred times.

The researchers tied the knot by compressing your house into the condensate from its borders. This made them initialize the quantum field in an explicit direction, after which they abruptly altered the implemented magnetic field to create an isolated null point, which caused the magnetic field to disappear. Then, the team waited for under a millisecond for the magnetic field to tie the knot.

“Now that we have seen these exotic beasts, we are really excited to study their peculiar properties. Importantly, our discovery connects to a diverse set of research fields including cosmology, fusion power, and quantum computers,” research group leader Mikko Möttönen said in a statement.

In mathematical terms, the quantum knot realizes a phenomenon called the Hopf fibration that was discovered by Heinz Hopf in 1931. The Hopf fibration is still commonly studied in physics and mathematics, and has now been experimentally demonstrated for the very first time.

“This is the beginning of the story of quantum knots. It would be great to see even more sophisticated quantum knots to appear such as those with knotted cores,” Möttönen said. “Also it would be important to create these knots in conditions where the state of the quantum matter would be inherently stable. Such system would allow for detailed studies of the stability of the knot itself.”

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Feature Image: Visualization of the structure of the created quantum knot. Each colorful band represents a set of nearby directions of the quantum field that is knotted. Note that each band is twisted and linked with the others once. Untying the knot requires the bands to separate, which is not possible without breaking them. (Credit: David Hall.)