This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Quantum technologies are considered key technologies of the future. However, research in this field requires not only scientific expertise but sometimes also highly specialized laboratory conditions.
Bose–Einstein condensates are a remarkable example, in which atoms move in lockstep, making quantum-mechanical effects visible not only at the level of individual atoms but also on a macroscopic scale. The first Bose–Einstein condensates were observed in ultracold atomic gases at temperatures close to absolute zero. The cooling required to achieve this was technically demanding, costly and restricted to specialized laboratories.
Today, quantum research is increasingly focusing on Bose–Einstein condensates in solid-state materials, which can also exist at moderate temperatures. Typically, electron-hole pairs in a semiconductor, known as excitons, are used for this purpose and can be selectively generated using laser pulses. Excitons, however, are too sluggish, so to speak, to move in lockstep and are therefore coupled to the light field of an optical resonator to reduce their effective mass.
The result is a hybrid state of matter and light known as exciton–polaritons. They offer the best of both worlds: They can be controlled using laser pulses and, because they are significantly lighter, can more easily be brought into a collective quantum-mechanical state. An exciton–polariton condensate is therefore a macroscopic quantum state that emits light and can form with significantly less external cooling, in some cases even without any external cooling at all.
These condensates are consequently considered a promising platform for future applications in quantum communication, quantum optics and quantum computing. A key challenge, however, is to control the properties of the condensate and, thus, the light it emits—a challenge that has now been overcome. An international research team has now shown that exciton–polariton condensates can be controlled through the magnetic properties of the material.
Instead of conventional semiconductor materials, the team used a novel layered magnetic semiconductor: chromium sulfide bromide (CrSBr). The team was led by professor Rupert Huber, Dr. Fabian Mooshammer and Dr.
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