A breakthrough in quantum simulation: Discovery of the long sought-after phase change

After decades of investigation, researchers observed a series of atoms undergoing a one-dimensional phase change. This was so elusive that it could only happen in a quantum simulator.

“There is only one motive [for our experiment] I'm trying to really understand basic physics. “We're just trying to understand the fundamental states that matter can be in,” he says. alexander shuckardt at the University of Maryland.

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

In it, they built a 1D ytterbium magnet one atom at a time. Previous calculations predicted that this type of magnet would become unmagnetized when warmed, thanks to quantum effects. However, no experiments have achieved this phase transition in the past.

One reason for the difficulty is that systems such as quantum computers and simulators typically only work properly when they are very cold. So heating them to cause a phase transition can cause them to malfunction, Schuckert says.

To get around this, he and his colleagues tuned the initial quantum state of the atoms so that over time, the collective state of the 1D magnet changes as if the temperature were increased. This revealed a phase transition that had never been seen before.

The result is very unusual, he says, because chains of atoms are generally not supposed to undergo phase transitions. Mohammad Maghrebi at Michigan State University. The researchers were able to manipulate it precisely because each ion could interact with other ions over large distances, even if they weren't in contact. This caused the entire line to engage in abnormal collective behavior.

Because their simulator allows for such exotic states of matter, it could be used to study theoretical systems that are extremely rare or may not exist in nature, Maghrebi said. say.

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 that to happen, these devices will have to be able to reach higher temperatures than they currently do. Currently, researchers can only create models at extremely low temperatures, but within five years it may be possible to simulate even higher temperatures, he says.

And if the simulator could be made larger, for example by arranging ions in two-dimensional arrays, many more existing theoretical systems could be studied, he says. andrea trombettoni at the University of Trieste, Italy. “This would suggest new physics to explore,” he says.