Entangled electrons found in ‘strange metal’ could boost quantum computing

17 Jan 2020

Image: © Peter Jurik/Stock.adobe.com

An international research team has observed quantum entanglement in a ‘strange metal’, with findings that could aid in the development of advanced computing.

New research published to Science by a team from Rice University and Vienna University of Technology (TU Wien) has revealed the first observance of “billions of billions” of flowing electrons in a quantum critical material. The discovery was made in a “strange metal” compound of ytterbium, rhodium and silicon as it both neared and passed through a critical transition at the boundary between two well-studied quantum phases.

By better understanding how such metals behave, the team said, it could open the door to new technologies in computing, communications and more.

“When we think about quantum entanglement, we think about small things,” said Qimiao Si, the study’s co-author.

“We don’t associate it with macroscopic objects. But at a quantum critical point, things are so collective that we have this chance to see the effects of entanglement, even in a metallic film that contains billions of billions of quantum mechanical objects.”

To see quantum entanglement in action, the team developed a highly complex materials synthesis technique to produce ultra-pure films containing one part ytterbium for every two parts rhodium and silicon (YbRh2Si2). At absolute-zero temperature, the material undergoes a transition from one quantum phase that forms a magnetic order, to another that does not.

‘Marvel at the wonder of nature’

Silke Bühler-Paschen, corresponding author of the paper, said: “With strange metals, there is an unusual connection between electrical resistance and temperature.

“In contrast to simple metals such as copper or gold, this does not seem to be due to the thermal movement of the atoms, but to quantum fluctuations at the absolute zero temperature.”

Seeing it was no easy feat, however, as to observe optical conductivity it needed to be seen at the terahertz frequency range. Yet less than 0.1pc of the total terahertz radiation was transmitted when passed through a detector, requiring many more hours of readings at different temperatures – as low as 1.4 Kelvin – before quantum entanglement was seen occurring.

Even producing the films came with immense challenges, requiring a custom-made ultra-high vacuum chamber with two electron-beam evaporators.

“Quantum entanglement is the basis for storage and processing of quantum information,” Si said.

“Our findings suggest that the same underlying physics – quantum criticality – can lead to a platform for both quantum information and high-temperature superconductivity. When one contemplates that possibility, one cannot help but marvel at the wonder of nature.”

Colm Gorey was a senior journalist with Silicon Republic