On the left, there is a bunch of magnets in a stable configuration. The system appears not to be magnetised on average. Floquet engineering has stopped the reorientation of the magnets. Despite the disorder, the quantum magnets maintain their aligned configuration. Sebastian Geier has a credit.
Nature's interactions determine the forces between particles, atoms, Molecules and even magnets. Two bar magnets are aligned under the influence of magnetic forces. A team led by Prof. Dr. Weidemller and Dr. Zrn at the Center for Quantum Dynamics at the University of Heidelberg succeeded in changing the nature of the interaction between quantum magnets. Magnets prepared for a long period of time can maintain their original orientation, instead of falling into a state of complete disorder. The physicists at Heidelberg demonstrated a control of spin interactions in isolated quantum systems.
When a system is prepared in an unstable configuration, it can exhibit surprising behavior. A reorientation of the magnets is possible if the bar magnets are aligned in the same direction. This results in an equilibrium in which all magnets are randomly oriented. The majority of investigations used to be limited to classical magnetic dipoles, but recently it has become possible to expand the approaches to quantum magnets using what are called quantum simulators. Synthetic atomic systems mimic the fundamental physics of magnetic phenomena in an extremely well-controlled environment where all relevant parameters can be adjusted almost at will.
The researchers used a gas of atoms that was cooled down to a temperature that was absolute zero. The atoms were excited to high electronic states using laser light, which separated the electron from the atomic nucleus. The atoms interact with each other over distances of almost a hair's breadth. The same characteristics of interacting quantum magnets are present in an ensemble of Rydberg atoms.
The trick of the physicists was to use methods from the field of nuclear magnetic resonance to steer the dynamics of the quantum magnets. The researchers apply microwave waves to modify the atomic spin. Floquet engineering is a technique used to control the interaction between atomic spins. The atoms were super-sensitive at the same time to any external perturbation, however tiny, like minute electric fields, and had to be applied at a billionth of a second. Sebastian Geier explains that they succeeded in stalling the spin's seemingly inevitable reorientation and maintaining a macroscopic magnetisation through their control protocol. It should now be possible to reverse the timelines using our Floquet engineering approach. It would be like a broken glass magically reassembling itself after it has been damaged.
Basic processes in complex quantum systems can be better understood with the studies. "After the first and second quantum revolution, which led to the understanding of the systems and the precise control of single objects, we are confident that our technique of dynamically adjusting interactions in a programmable fashion opens a path to Quantum Technologies 3.0," says Professor Weidemller.
Sebastian Geier et al, Floquet Hamiltonian engineering of an isolated many-body spin system, Science, is more information. There is a science.abd9547
There is a programmable interaction between quantum magnets on November 29, 2021.
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