By adding some magnetic flair to an exotic quantum experiment, physicists produced an ultra-stable one-dimensional quantum gas with never-before-seen “scar” states – a feature that could someday be useful for securing quantum information.

As the story goes, the Greek mathematician and tinkerer Archimedes came across an invention while traveling through ancient Egypt that would later bear his name. It was a machine consisting of a screw housed inside a hollow tube that trapped and drew water upon rotation. Now, researchers led by Stanford University physicist Benjamin Lev have developed a quantum version of Archimedes’ screw that, instead of water, hauls fragile collections of gas atoms to higher and higher energy states without collapsing. Their discovery is detailed in a paper published today (January 142021) in Science.

As the story goes, the Greek mathematician and tinkerer Archimedes came across an invention while traveling through ancient Egypt that would later bear his name. It was a machine consisting of a screw housed inside a hollow tube that trapped and drew water upon rotation. Now, researchers led by Stanford University physicist Benjamin Lev have developed a quantum version of Archimedes’ screw that, instead of water, hauls fragile collections of gas atoms to higher and higher energy states without collapsing. Their discovery is detailed in a paper published Jan. 14 in Science.

“My expectation for our system was that the stability of the gas would only shift a little,” said Lev, who is an associate professor of applied physics and of physics in the School of Humanities and Sciences at Stanford. “I did not expect that I would see a dramatic, complete stabilization of it. That was beyond my wildest conception.”

Along the way, the researchers also observed the development of scar states—extremely rare trajectories of particles in an otherwise chaotic quantum system in which the particles repeatedly retrace their steps like tracks overlapping in the woods. Scar states are of particular interest because they may offer a protected refuge for information encoded in a quantum system. The existence of scar states within a quantum system with many interacting particles—known as a quantum many-body system—has only recently been confirmed. The Stanford experiment is the first example of the scar state in a many-body quantum gas and only the second ever real-world sighting of the phenomenon.

Metals and insulators are the yin and yang of physics, their respective material properties strictly dictated by their electrons’ mobility — metals should conduct electrons freely, while insulators keep them in place.

So when physicists from Princeton University in the US found a quantum quirk of metals bouncing around inside an insulating compound, they were lost for an explanation.

We’ll need to wait on further studies to find out exactly what’s going on. But one tantalising possibility is that a previously unseen particle is at work, one that represents neutral ground in electron behaviour. They’re calling it a ‘neutral fermion’.

Basically speaking, metals conduct electricity and insulators don’t. On the molecular level, that comes down to how freely electrons can move through the materials – in metals, electrons are very mobile, while insulators obviously have high resistance that prevents them moving much.

As a side effect of this, metals can exhibit a phenomenon known as quantum oscillations. When exposed to a magnetic field at very low temperatures, electrons can shift into a quantum state that causes the material’s resistivity to oscillate. This doesn’t happen in insulators, however, since their electrons don’t move very well.