A team led by researchers at the University of Regensburg has shown that the magnetic order inside a layered semiconductor, chromium sulfide bromide (CrSBr), can change the energy of light emitted by an exciton-polariton condensate. In the reported experiment, adjusting the magnetism of the material shifted the emitted light’s energy, which means the quantum state of the light-emitting system was controlled through magnetism rather than through an electrical voltage. The work is a laboratory demonstration in quantum optics. It is not a consumer device, and it does not yet show a working quantum communication link.
What the experiment actually did
According to the university’s report, published by Phys.org on October 8, 2026, the team used ultrashort laser pulses to excite exciton-polaritons in a CrSBr-based structure. They then applied a magnetic field to change the magnetic order of the material. Changing that order altered the energy of the light the system emitted. The report presents this as direct control of a quantum state through the magnetism of the material itself.
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The primary paper is Heng Zhang et al., “Magnetic control of an exciton–polariton condensate in a van der Waals magnet,” Nature Materials (2026), DOI 10.1038/s41563-026-02751-y. Specialized apparatus parameters and sample conditions are reported there. This article relies on the university’s account for the details below and does not add measurements beyond it.
Exciton-polaritons and condensates, in plain terms
An exciton is a bound pair made of an electron and the hole it leaves behind in a semiconductor. When an exciton couples strongly to light trapped in an optical resonator, the combined object is called an exciton-polariton. It carries both matter and light characteristics.
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The light part matters for the physics. According to the report, it reduces the effective mass of the polariton, which makes collective quantum behavior easier to reach. When enough of these particles are packed into the same state, they can act coherently as one entity. That collective state is a condensate. In this experiment, the condensate emits light, and that emitted light is what the researchers measured and tuned.
What CrSBr is and where magnetism enters
CrSBr is a layered material. It is built from atomically thin layers stacked on one another. Within each layer, magnetic moments (spins) point in the same direction. Neighboring layers point in opposite directions. The report explains that this arrangement confines excitons to their own layers.
An external magnetic field can rotate the spins so that they align across layers. This changes the properties of the exciton-polaritons, including their energy. The report uses the phrase “magnetic cage” as an explanatory metaphor for this confinement. It is not a literal physical structure, and it should not be read as one.
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A condensate is not identified by a single signal. In this work, the report describes two observations at the condensation threshold. The emitted-light intensity rose more than a hundredfold, and the light waves became coherent, meaning their phases lined up. The first author, Dr. Heng Zhang, described the coherence as follows in the university’s report:
“Once the condensation threshold is reached, the intensity of the emitted light suddenly increases more than a hundredfold. At the same time, the light waves become ordered and, in a sense, oscillate in step with one another. This so-called coherence provides clear evidence of condensation.”
The hundredfold figure is a measured intensity change at threshold in this experiment. It describes a threshold transition under the conditions the team used. It is not a general performance rating for CrSBr or for light sources built on it.
Magnetic control of the emitted light
The most consequential claim is about tuning. Co-first author Christian Weidgans, as quoted in the university’s report, compared the magnetic approach with earlier methods:
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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware match“While previous approaches have relied, among other methods, on applying an electrical voltage, even moderate magnetic fields in CrSBr enable a shift in the energy of the emitted light that is up to 10 times larger. In this way, the quantum state can be controlled directly through the magnetism of the material.”
Two qualifications apply. First, the “up to 10 times larger” comparison is Weidgans’s statement about energy shifts relative to earlier approaches, as reported by the university. The underlying comparison data sit in the Nature Materials paper, so readers should treat the figure as an attributed claim until they have checked that paper. Second, “up to” marks a maximum, not a typical result.
What is demonstrated and what is still prospective
The report separates the experiment from its future uses. The experiment demonstrates magnetic control of an exciton-polariton condensate and of its emitted light. The authors describe several directions that the platform could support, but these are not results of the reported experiment:
- Direct coupling of condensate light to magnetic states. Co-first author Dr. Niloufar Nilforoushan said: “In the future, the platform could be used to directly couple the light emitted by the condensate to magnetic states and manipulate it on extremely short time scales.”
- Microwave influence on magnetic order. Proposed, not demonstrated here.
- Magnetic-memory integration. Proposed, not demonstrated here.
- Microwave-to-optical conversion. Proposed, not demonstrated here.
Quantum communication, which many readers ask about first, falls into the same category. The report does not describe a communication channel, a transmitted quantum signal, or a device that sends information. Any link to quantum networks is a long-term possibility rather than a finding.
Related CrSBr work from a separate team
Readers who search this topic may also find a 2026 commentary in Light: Science & Applications. Konstantinos S. Daskalakis wrote a News & Views piece, “A magnetic dial for exciton-polaritons,” dated August 21, 2026, on work by Li et al. That study measured magnetic tuning of exciton-polariton coupling strength and nonlinearity in CrSBr. It is a different study from the condensate experiment described above, and its measurements should not be merged with those reported by the Regensburg team.
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The commentary states: “Experiments in the van der Waals magnet CrSBr show that magnetic fields can strongly tune exciton-polariton coupling strength and optical nonlinearity.” It reports Rabi splitting values of about 632 meV at 6 K and about 745 meV at room temperature for a representative flake, and a decrease of nearly 100 meV within a few tenths of a tesla for the Li et al. study. These figures come from Daskalakis’s commentary, not from the Regensburg report, and they describe that separate study’s conditions.
Bottom line for readers
The Regensburg-led team showed that magnetic order in CrSBr can control an exciton-polariton condensate and shift the energy of its emitted light. The evidence for condensation is a greater-than-hundredfold intensity jump with coherent emission at threshold. The magnetic-control comparison with earlier voltage-based approaches is an attributed claim pending the full paper. Quantum communication, magnetic memory and microwave-to-optical conversion remain future possibilities that the authors describe, not results of this experiment.
Sources: Phys.org report provided by the University of Regensburg, October 8, 2026; Konstantinos S. Daskalakis, “A magnetic dial for exciton-polaritons,” Light: Science & Applications, August 21, 2026.
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