A major hurdle for work at the forefront of fundamental physics is the
inability to test cutting-edge theories in a laboratory setting. But a
recent discovery opens the door for scientists to see ideas in action that
were previously only understood in theory or represented in science fiction.
One such theory is on the Unruh effect. When astronauts in a spacecraft
undergo super strong acceleration and see the light of stars stream by, then
the Unruh effect is an additional warm glow on top of the streaming light.
First predicted by Canadian physicist Bill Unruh, this effect is closely
related to the glow from black holes predicted by Stephen Hawking. This is
because black holes strongly accelerate everything towards them.
“Black holes are believed to be not entirely black,” says Barbara Šoda, a
PhD student in physics at the University of Waterloo. “Instead, as Stephen
Hawking discovered, black holes should emit radiation. This is because,
while nothing else can escape a black hole, quantum fluctuations of
radiation can.”
Similar to how the Hawking effect needs a black hole, the Unruh effect
requires enormous accelerations to produce a significant glow. The Unruh
effect was therefore thought to be so weak that it would be impossible to
measure with the accelerations that can be achieved in experiments with
current technology.
The research team found an innovative way to experiment on the Unruh effect
through a novel use of high-intensity lasers. They discovered that shining a
high-intensity laser on an accelerated particle can amplify the Unruh effect
so much that it actually becomes measurable.
In an unexpected twist, the team also discovered that by delicately
balancing acceleration and deceleration, one should even be able to make
accelerated matter transparent.
The ability to experiment on the Unruh effect as well as on the new
phenomenon of acceleration-induced transparency provide a big boost for
physicists, who have long been searching for ways to unify Einstein’s theory
of general relativity with quantum mechanics.
“The theory of general relativity and the theory of quantum mechanics are
currently still somewhat at odds, but there has to be a unifying theory that
describes how things function in the universe,” says co-author Achim Kempf,
a professor of applied mathematics and member of the Institute for Quantum
Computing at Waterloo. “We’ve been looking for a way to unite these two big
theories, and this work is helping to move us closer by opening up
opportunities for testing new theories against experiments.”
The team is now setting out to conduct further laboratory experiments. They
are also excited by the impacts of the research on some of the fundamental
questions about physics and the nature of the universe.
“For over 40 years, experiments have been hindered by an inability to
explore the interface of quantum mechanics and gravity,” says co-author
Vivishek Sudhir, an assistant professor of mechanical engineering at the
Massachusetts Institute of Technology and an affiliate of the Laser
Interferometer Gravitational-Wave Observatory (LIGO). “We have here a viable
option to explore this interface in a laboratory setting. If we can figure
out some of these big questions, it could change everything.”
The new paper by Šoda, Sudhir and Kempf, “Acceleration-induced effects in
stimulated light-matter interactions,” is published in the latest edition of
the journal Physical Review Letters.
Reference:
Barbara Šoda, Vivishek Sudhir, and Achim Kempf, Acceleration-Induced
Effects in Stimulated Light-Matter Interactions, Phys. Rev. Lett. 128,
163603 – Published 21 April 2022 DOI: 10.1103/PhysRevLett.128.163603
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Physics