To speed up the writing and readout of magnetic information from storage devices, researchers are exploring the use of ultrashort laser pulses that can switch magnetic domains in solid-state materials. Although this route shows promise, the large number of magnetic materials interacting with one another, in a so-called quantum many-body system, has made this approach difficult to study. Exposing materials to intense laser pulses makes it possible to induce metal-insulator transitions, to control magnetic order and to generate transient superconducting behavior. However, pinning down the mechanisms underlying these phenomena is often difficult because the response of a material to irradiation is governed by complex, many-body dynamics. Experiments in which atoms were immersed in a shaken crystal made of light provide novel insight that might be helpful in understanding the fundamental behavior of magnetic storage devices. Courtesy of Michael Messer, ETH Zürich. To obtain insight into the physics at play in this many-body system, researchers at ETH Zürich simulated magnetic materials using electrically neutral magnetic atoms that they trapped in an artificial crystal made of light. The simulated system was governed by the same basic physical principles as the storage system. However, in contrast to the solid-state environment, the simulated system eliminated many unwanted effects resulting from impurities in the material; and all key materials in the simulated system could be finely tuned. This both reduced the complexity of the simulated system and increased researchers’ ability to control it. Using a microscopic model of the system, the team was able to control particle tunneling and magnetic exchange energies independently and identify ways to enhance and manipulate the magnetic order in the storage system. Specifically, the team demonstrated that antiferromagnetic correlations in a fermionic many-body system could be reduced, enhanced or even switched to ferromagnetic correlations. The fundamental understanding gained from these experiments could help researchers identify and understand materials that could serve as the basis for the next generation of data-storage media. The research was published in Nature (doi:10.1038/nature25135).