Researchers from Stockholm University and IISER Mohali have proposed a practical way to detect the Unruh effect, which suggests that accelerating objects perceive empty space as warm. Their approach uses atoms between mirrors to produce a timed burst of light, revealing the effect through superradiance. This method lowers the acceleration needed, making the phenomenon accessible in standard labs.
The Unruh effect, a prediction from quantum field theory, posits that an accelerating observer would detect a faint thermal radiation in what appears as empty vacuum to a stationary one. Directly observing this requires accelerations far beyond current experimental reach, but scientists have now outlined a feasible detection strategy.
In their proposal, atoms are positioned between two high-quality parallel mirrors. These mirrors modify the atoms' light emission, enabling superradiance—a collective emission where atoms synchronize like a choir, producing a brighter and faster light burst. The subtle warmth from the Unruh effect during acceleration advances this burst's timing, serving as a detectable signature.
"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."
This technique reduces the necessary acceleration dramatically, as the mirrors amplify the signal. "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."
The work, co-authored by Kinjalk Lochan and Sandeep K. Goyal from IISER Mohali, bridges lab experiments with extreme physics concepts. Since acceleration relates to gravity, such methods could probe quantum gravity effects on a benchtop. The findings appear in Physical Review Letters.
