A subtle timing flash may expose the Unruh effect. The approach ties ordinary lab tools to deep quantum physics.

Researchers at Stockholm Universityy and the Indian Institute of Science Education and Research (IISER) Mohali have identified a practical method for detecting one of physics’ most unusual predictions: the Unruh effect. This effect suggests that an object that accelerates would sense empty space as slightly warm.

Directly creating that warmth through extreme acceleration is far beyond laboratory capabilities, but the team demonstrates how this subtle phenomenon can be transformed into a detectable, precisely timed flash of light.

How atoms and mirrors amplify tiny quantum signals

Picture a row of atoms placed between two facing mirrors. These mirrors influence how quickly the atoms emit light. When the atoms interact collectively, they can release light in a powerful, synchronized burst similar to a choir singing together, a process known as superradiance.

The new research shows that if the atoms experience the slight warming linked to acceleration, that collective burst happens sooner than it normally would. The shift toward an earlier flash becomes a clear and detectable sign of the Unruh effect.

Turning a whisper of acceleration into a measurable flash

“We’ve found a way to turn the Unruh effect’s whisper into a shout,” said Akhil Deswal, a PhD student at IISER Mohali. “By using carefully spaced high-quality mirrors, we make ordinary background signals quieter while the acceleration-seeded burst comes out early and clean.”

Importantly, the setup requires far less acceleration than would otherwise be needed without these high-quality mirrors.

“Timing is the key,” added Navdeep Arya, a postdoctoral researcher at Stockholm University. “The choir of atoms is not only louder but also shouts earlier if they feel the faint Unruh effect-related warmth of empty space. That simple clock-like marker can make it easier to separate the Unruh signal from everyday noise.”

By theoretically addressing a decades-old detection challenge, the idea opens a bridge between available laboratory devices and phenomena usually linked to extreme conditions. Because acceleration and gravity are closely related, similar timing tricks might one day help researchers probe subtle, gravity-driven quantum effects — right on the lab bench.

Reference: “Time-Resolved and Superradiantly Amplified Unruh Effect” by Akhil Deswal, Navdeep Arya, Kinjalk Lochan and Sandeep K. Goyal, 27 October 2025,Physical Review Letters.
DOI: 10.1103/6z1l-kkmk

A .D. acknowledges funding from IISER Mohali. The research of K.

L. is partially supported by Anusandhan National Research Foundation (ANRF), Government of India, through MATRICS Research Grant No. MTR/2022/000900.

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