Physicists have observed a new state of matter at work inside an elusive thread of quantum gas.
The gossamer-thin strings of gas capable of binding giants sound like items worthy of a quest in Grimms’ fairy tales. But versions of these materials are theoretically possible in physics – unfortunately though, in practice they inevitably collapse on forming.
Researchers from Stanford University in the US have now found they can create such a material that’s stable enough to resist collapsing into a cloud, even under considerable force. What’s more, they’ve identified a new state of matter at work that has only ever been seen once before – and never in quantum gas before now.
Importantly, the quantum properties of this gas might earn it a place in future generations of information technology.
The category of matter at work even has a legendary title; a super Tonks-Girardeau gas. It consists of atoms cooled to a point that they begin to lose their sense of individual identity, constrained to form a conga-line held in check by their collective forces.
Under ideal conditions, attraction between the particles within this drawn-out thread of quantum gas could keep it in line even under duress. Hence why physicists describe it as ‘super’.
Yet inside less-than-perfect laboratory equipment, even the most delicately tuned super Tonks-Girardeau gases fail to remain stable for very long, contracting into a ball in no time.
Physicist Benjamin Lev wondered if the element dysprosium would make for a more robust candidate. With one of the highest magnetic strengths on the periodic table, it might hold its own a little longer, with a little support.
“The magnetic interactions we were able to add were very weak compared to the attractive interactions already present in the gas. So, our expectations were that not much would change,” says Lev.
“Wow, were we wrong.”
It turns out a tuned super Tonks-Girardeau gas based on dysprosium is just what the hero ordered. No matter what the team did to it, it kept form.
Even cranking the quantum system into higher energy states failed to push the string into a messy haze of quantum-smeared particles.
Probing the mechanics of the process, the team soon noticed the hallmarks of a rather elusive phenomenon called quantum many-body scarring.
This weird state of matter sits somewhere between quantum chaos and the predictability of old-fashioned classical physics, and describes a world that seems counterintuitive at first glance.
A quarter of a century ago, it was discovered that in the buzz of a quantum system – where particles are everywhere and nowhere at once and individual atoms lose their sense of self – it’s possible for predictable states to emerge.
These scars resemble pathways worn across a football pitch. While players freely chase the ball all over the field, some directions seem to be preferred over others.
The perplexing thing about quantum scarring is how they fit with thermodynamics. Raise the temperature on a group of particles and they’ll simply bounce around more, redistributing the heat energy until all bodies have a roughly equal share.
Quantum many-body scarring runs counter to this rule of equilibrium, holding a preference for some states no matter how much the excitement grows around them.
The phenomenon has been seen once before in a queue of rubidium atoms, but never in a quantum gas. So finding signs of the state in a cooled string of dysprosium atoms has the potential to reveal a great deal about how bodies in a quantum system share energy.
Given we’re destined for a future filled with quantum technologies, we’re going to need to know as much as possible about how to remove heat from the computers of tomorrow.
But quantum scars could be potentially useful for the storage of quantum information in their own right, or serving as a kind of simulator in the lab for studying quantum systems.
Speculation over practical uses aside, Lev sees the work as fundamental to understanding the quantum landscape. Applications can come later.
“If you compare quantum science to where we were when we discovered what we needed to know to build chemical plants, say, it’s like we’re doing the late 19th-century work right now,” says Lev.
A quantum-scarred thread of gas is just the start of a quest into some truly amazing destinations.
This research was published in Science.