Strange loops in the fabric of reality have finally been witnessed forming in a super cold gas, providing physicists with an opportunity to study the behaviors of a rather peculiar kind of one-sided magnetism.
Known as ‘Alice rings’ after the Alice of ‘Wonderland’ fame, the circular structures were observed by a collaboration between researchers in the US and Finland which already has a long list of discoveries concerning the distortions in quantum fields known as topological monopoles.
The isolated equivalent of a pole on a magnet, monopoles truly sound like something Alice would have seen in her hunt for the white rabbit. Cutting a magnet in half won’t succeed in separating its north from south, but monopoles can theoretically arise in the quantum machinery that gives rise to various forces and particles.
One version of the monopole takes the form of an elementary particle, one that has defied all attempts to identify so remains, for now, purely hypothetical.
Yet monopoles can emerge in other settings. The frothing of various quantum fields can give rise to their own style of one-sided magnetism as they swirl, pulling and tugging on their surrounds to give birth to short-lived anomalies that stand out for a split moment before vanishing into the churn once more.
As a member of the Monopole Collaboration from Aalto University in Finland, physicist Mikko Möttönen is intimately familiar with a whole variety of whirlpools, strings, and tangles that can emerge in the weave of a quantum fabric.
In 2015, just a year after proving a topological monopole’s existence, Möttönen and his colleagues triumphantly succeeded in observing one in isolation for the first time in an ultra-cold state of rubidium atoms called a Bose-Einstein condensate (BEC).
“We are the only ones who have been able to create topological monopoles in quantum fields,” Möttönen explained to ScienceAlert.
“After creating them, it took some time for us to also study quantum knots and skyrmions before we had a close look at what happens to the topological monopole right after it has been created.”
Less than two years after their initial observation, the collaboration made a surprise discovery – monopoles could decay into other types.
In this latest investigation, the researchers again watched a topological monopole melt into something else, only this time the end result was more like a tiny doorway into Wonderland – structures named Alice strings.
Alice strings are closely associated with monopoles, twisting into one-sided magnetic poles whenever they close into loops. And those loops of Alice strings are known as Alice rings.
Yet while typical monopoles might last a few thousandths of a second, Alice rings stick around for more than 80 milliseconds – some 20 times longer.
“From a distance, the Alice ring just looks like a monopole, but the world takes a different shape when peering through the center of the ring,” says David Hall, a physicist from Amherst College in the US.
Like Alice’s own looking glass, passing through the strange magnetic loop in a BEC’s quantum field can turn everything on its head. Other monopoles that happen to fall through become reversed into their mirror-versions, flipping the ring into its opposite as they slide on through.
While the team have yet to observe this inversion experimentally, catching sight of the ring’s formation in the decay of a topological monopole is exciting progress.
On a practical level, we can only speculate how the finding might be applied. But the more we learn about the unstable nature of quantum fields, the better we might be able to map their waters and understand deeper truths of reality.
“Primarily, this creation of Alice rings is of fundamental importance,” Möttönen tells ScienceAlert.
“It casts light and inspiration to the search of the deepest constituents of the Universe, matter, and information.”
This research was published in Nature Communications.