Elusive phase change finally spotted in a quantum simulator

After decades of looking, researchers have seen a chain of atoms undergo a 1D phase change so elusive that it could only happen inside a quantum simulator.

“One motivation (for our experiment) is to try to understand fundamental physics. We’re trying to understand the fundamental states in which matter can exist,” he says. Alexander Schuckert at the University of Maryland.

He and his colleagues used electromagnetic fields to organize 23 ions of the element ytterbium in a line, forming an almost one-dimensional chain. This device can be used for quantum computing, but in this case, the researchers used the string as a simulator instead.

Inside it, they built a 1D ytterbium magnet one atom at a time. Previous calculations predicted that this type of magnet would become demagnetized when heated, thanks to quantum effects. But no past experiment had achieved this phase transition.

One reason for the difficulty is that systems like quantum computers and simulators usually only work when they are very cold. Heating the phase transition to occur can therefore lead to breakdowns, says Schuckert.

To avoid this, he and his colleagues tuned the initial quantum state of the atoms so that over time the collective state of the 1D magnet changed as if its temperature had increased. This revealed an unprecedented phase transition.

The achievement is very exotic because chains of atoms should not generally undergo phase transitions, he says. Mohammad Maghrebi at Michigan State University. Only the researchers were able to engineer it because each ion could interact with others that were far away from it, even if they weren’t touching. This pushed the entire line into unusual collective behavior.

Because their simulator makes exotic states of matter possible, it could be used to study theoretical systems that may be very rare – or non-existent – ​​in nature, says Magrebi.

Schuckert suggests that quantum simulators could also help explain the strange electrical or magnetic behavior that some materials exhibit. in the real world. But for this, these devices must be able to reach higher temperatures than today. Currently they can only model very cold temperatures, but within five years simulations of higher temperatures may be possible, he says.

And more theoretical systems that still exist and could be studied, that the simulators could be made bigger, for example by arranging the ions. two-dimensional matriceshe says Andrea Trombettoni at the University of Trieste in Italy. “This will suggest new physics to explore,” he says.