Physicists have figured out a way to see the elusive ‘Unruh effect’ in the lab


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Illustration: Carl Gustafson

A group of physicists claim that discovered two properties of accelerating matter that they believe could make a previously unseen type of radiation visible. Newly Described properties mean that the observation of radiation, called the Unruh effect, can occur in a benchtop laboratory experiment.

The Unruh effect in nature theoretically requires incredible acceleration to be seen.and because it is only visible from the point of view of an accelerating object in a vacuum, it is nearly impossible to see. But thanks to recent advances, the Unruh effect can be observed in laboratory experiments.

In a new study, a team of scientists describe two previously unknown aspects of the quantum field, which could mean that the Unruh effect can be observed directly. First, the effect can be stimulated, which means that a normally weak effect can become more noticeable under certain conditions. The second phenomenon is that a sufficiently excited accelerating atom can become transparent. The team’s research was published this spring in Physical Review Letters.

The Unruh effect (or the Fulling-Davis-Unruh effect, named after the physicists who first proposed its existence in the 1970s) is a phenomenon predicted by quantum field theory, which states that an object (be it a particle or a spaceship) acceleration in a vacuum will glow, although this glow is notbe visitingable any external observer also not accelerating in a vacuum.

“Transparency caused by acceleration means that it makes the Unruh effect detector transparent to everyday transitions due to the nature of its motion,” said Barbara Schoda, a physicist at the University of Waterloo and lead author of the study, in a video call. with Gizmodo. Just as Hawking radiation is emitted by black holes when their gravity pulls particles in, the Unruh effect is emitted by objects as they accelerate through space.

There are several reasons why the Unruh effect has never been observed directly. First, the effect requires a ridiculous linear acceleration; to reach a temperature of 1 kelvin, at which an accelerating observer would see a glow, the observer should speed upin 100 quintillion meters per second squared. The glow of the Unruh effect is thermal; if the object accelerates faster, the glow temperature will be warmer.

Previous methods for observing the Unruh effect were suggested. But this the team believes they have a compelling chance of seeing the effect, thanks to their findings about the properties of the quantum field.

“We would like to build a dedicated experiment that can unambiguously detect the Unruh effect and then provide a platform to explore various related aspects,” said Vivishek Sudhir, a physicist at the Massachusetts Institute of Technology and co-author of the recent work. “Unambiguity is the key adjective here: in a particle accelerator, bunches of particles are actually accelerated, which means that it becomes very difficult to deduce the extremely subtle Unruh effect among the various interactions between particles in a bunch.”

“In a sense,” Sudhir concluded, “we need to make a more accurate measurement of the properties of a well-identified single accelerated particle, and particle accelerators are not designed for this.”

Hawking radiation is thought to be emitted by black holes like these two taken by the Event Horizon telescope.

Hawking radiation is thought to be emitted by black holes like these two taken by the Event Horizon telescope.
Image: Cooperation with ECT

The essence of their proposed experiment is to stimulate the Unruh effect in the laboratory using an atom as an Unruh effect detector. By exploding a single atom with photons, the team will elevate the particle to a higher energy state, and its acceleration-induced transparency will drown out the particle for any day-to-day noise that would obscure the presence of the Unruh effect.

By hitting a particle with a laser, “you increase the chance of seeing the Unruh effect, and the chance increases with the number of photons in the field,” Shoda said. “And that number can be huge, depending on how strong your laser is.” In other words, since the researchers could particle with quadrillion Photons, they increase the probability of the Unruh effect occurring by 15 orders of magnitude.

Since the Unruh effect is similar in many ways to Hawking radiation, the researchers believe that two properties of the quantum field they recently described can be used to stimulate Hawking radiation and imply the existence of gravity-induced transparency. Since Hawking radiation has never been observed, the discovery of the Unruh effect could be a step towards better understanding of the theoretical glow around black holes.

Of course, these results don’t mean much if the Unruh effect can’t be observed directly in the lab — that’s the researchers’ next step. Just when that the experiment will be carried out, however, remains to be seen.

Read more: Lab black hole shows Stephen Hawking was right, obviously

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