quantum magnet

In an investigation it has been possible to reproduce a theoretical model by means of an artificial quantum system. The results, which show how the system becomes a quantum magnet, could have applications in metrology or quantum computing.

The study is the work of a team that includes scientists from the Charles Fabry Laboratory (Paris-Saclay University in France, CNRS (French National Center for Scientific Research) and Institute of Optics) and the Higher Council for Scientific Research (CSIC) in Spain. .

An experiment carried out at the Charles Fabry Laboratory as a main part of the research has experimentally shown new magnetic phases of matter in a quantum simulator.

Cheng Chen of the University of Paris-Saclay and his colleagues have been able to observe long-range ferromagnetic order in a quantum spin system. The results, which could have applications in metrology or quantum computing, show that the fundamental features of this theoretical model can be implemented and measured in artificial quantum systems and could allow the observation of other phenomena that are difficult to calculate numerically.

Electrons not only have charge, but also another property that manifests itself in extremely small devices, which require quantum mechanics to describe: spin. Starting from a state where all the spins are aligned “down”, through the controlled application of laser and microwave pulses, the team has prepared low-energy states of the system in two complementary situations: the ferromagnetic case, where all the spins tend to oriented in a single direction in the horizontal plane, and the antiferromagnetic case, where neighboring spins align in opposite horizontal directions.

Fluorescence of a square array of 100 individual rubidium atoms. (Image: Institut d’Optique / CNRS)

“In an extraordinary way, and in accordance with recent theoretical predictions, only the ferromagnetic case allows us to observe a long-range magnetic order: the system becomes a quantum magnet, something that is impossible in two dimensions in conventional materials,” he explains. Daniel Barredo, a CSIC researcher at the Nanomaterials and Nanotechnology Research Center (CINN) who has collaborated on the study.

Theoretical groups from the University of Harvard and Berkeley, in the United States, and from Innsbruck in Austria have also participated in the work.

The study is titled “Continuous Symmetry Breaking in a Two-dimensional Rydberg Array”. And it has been published in the academic journal Nature. (Source: CSIC)