# First Quantum Knot Finally Created

Scientists have long predicted the possibility of tying knots in quantum fields, but no one has been able to observe, let alone make, a 3-D quantum knot until now.

David Hall and Mikko Mottonen have created knotted solitary waves, known as knot solitons, in superfluid by manipulating magnetic fields. "Knots" are mathematically defined as closed curves in 3D spaces. A knot soliton consists of an infinite number of rings, each linked with all of the others to generate a toroidal (or donut-like) structure. Previous experiments have identified solitons in one and two dimensions, but the knot solitons created by the team are the first to be documented in all three spatial dimensions.

"For decades, Physicists have been theoretically predicting that it should be possible to have knots in quantum fields, but nobody else has been able to make one," says Prof. Mottonen. "Importantly, our discovery connects to a diverse set of research fields including cosmology, fusion power, and quantum computers."

The knots exist within a tiny droplet of superfluid that is just barely visible to the human eye, is less than 10 microns across, and was tied in less than a thousandth of a second. But even such a small creation can have potentially big impacts on various scientific fields. Mathematically speaking, the created quantum knot has significant implications for the Hopf Fibration- a mathematical description of a four-dimensional sphere. The Hopf Fibration is still widely studied in physics and math, and now, with the discovery of the first quantum knot, it has been experimentally demonstrated for the first time in a quantum field.

Hall and Mottonen tied the knot by exposing a rubidium condensate to raid changes of a specifically tailored magnetic field, squeezing the structure into the condensate from its outskirts. Unlike, say, knotted rope, these quantum knots cannot be untied without breaking their internal structure.

David Hall and Mikko Mottonen have created knotted solitary waves, known as knot solitons, in superfluid by manipulating magnetic fields. "Knots" are mathematically defined as closed curves in 3D spaces. A knot soliton consists of an infinite number of rings, each linked with all of the others to generate a toroidal (or donut-like) structure. Previous experiments have identified solitons in one and two dimensions, but the knot solitons created by the team are the first to be documented in all three spatial dimensions.

"For decades, Physicists have been theoretically predicting that it should be possible to have knots in quantum fields, but nobody else has been able to make one," says Prof. Mottonen. "Importantly, our discovery connects to a diverse set of research fields including cosmology, fusion power, and quantum computers."

The knots exist within a tiny droplet of superfluid that is just barely visible to the human eye, is less than 10 microns across, and was tied in less than a thousandth of a second. But even such a small creation can have potentially big impacts on various scientific fields. Mathematically speaking, the created quantum knot has significant implications for the Hopf Fibration- a mathematical description of a four-dimensional sphere. The Hopf Fibration is still widely studied in physics and math, and now, with the discovery of the first quantum knot, it has been experimentally demonstrated for the first time in a quantum field.

Hall and Mottonen tied the knot by exposing a rubidium condensate to raid changes of a specifically tailored magnetic field, squeezing the structure into the condensate from its outskirts. Unlike, say, knotted rope, these quantum knots cannot be untied without breaking their internal structure.

"First we cooled a gas of rubidium atoms down to billionths of a degree above zero, at which point it became a superfluid- a tiny, well-ordered environment in which these particle-like objects can exist," explains Prof. Hall. "Then we exposed the superfluid to a rapid change of a specifically tailored magnetic field."

"The next step is to see what these quantum knots can do. Now that we've created these particles, we can begin experimenting with them and studying their properties," explains Prof. Hall.

"This is the beginning of the story of quantum knots," said Mottonen. "It would be great to see even more sophisticated quantum knots to appear such as those with knotted cores."

"This is the beginning of the story of quantum knots," said Mottonen. "It would be great to see even more sophisticated quantum knots to appear such as those with knotted cores."