Louisiana State University physicists have leveraged quantum information
theory techniques to reveal a mechanism for amplifying, or "stimulating,"
the production of entanglement in the Hawking effect in a controlled manner.
Furthermore, these scientists propose a protocol for testing this idea in
the laboratory using artificially produced event horizons. These results
have been recently published in Physical Review Letters, "Quantum aspects of
stimulated Hawking radiation in an analog white-black hole pair," where Ivan
Agullo, Anthony J. Brady and Dimitrios Kranas present these ideas and apply
them to optical systems containing the analog of a pair white-black hole.
Black holes are some of the most mystifying objects in our universe, largely
due to the fact that their inner-workings are hidden behind a completely
obscuring veil—the black hole's event horizon.
In 1974, Stephen Hawking added more mystique to the character of black holes
by showing that, once quantum effects are considered, a black hole isn't
really black at all but, instead, emits radiation, as if it was a hot body,
gradually losing mass in the so-called "Hawking evaporation process."
Further, Hawking's calculations showed that the emitted radiation is quantum
mechanically entangled with the bowels of the black hole itself. This
entanglement is the quantum signature of the Hawking effect. This astounding
result is difficult, if not impossible, to be tested on astrophysical black
holes, since the faint Hawking radiation gets overshined by other sources of
radiation in the cosmos.
On the other hand, in the 1980's, a seminal article by William Unruh
established that the spontaneous production of entangled Hawking particles
occurs in any system that can support an effective event horizon. Such
systems generally fall under the umbrella of "analog gravity systems" and
opened a window for testing Hawking's ideas in the laboratory.
Serious experimental investigations into analog gravity systems—made of
Bose-Einstein condensates, non-linear optical fibers, or even flowing
water—have been underway for more than a decade. Stimulated and
spontaneously-generated Hawking radiation has recently been observed in
several platforms, but measuring entanglement has proved elusive due to its
faint and fragile character.
"We show that, by illuminating the horizon, or horizons, with appropriately
chosen quantum states, one can amplify the production of entanglement in
Hawking's process in a tunable manner," said Associate Professor Ivan
Agullo. "As an example, we apply these ideas to the concrete case of a pair
of analog white-black holes sharing an interior and produced within a
non-linear optical material."
"Many of the quantum information tools used in this research were from my
graduate research with Professor Jonathan P. Dowling," said 2021 Ph.D.
alumnus Anthony Brady, postdoctoral researcher at the University of Arizona.
"Jon was a charismatic character, and he brought his charisma and
unconventionality into his science, as well as his advising. He encouraged
me to work on eccentric ideas, like analog black holes, and see if I could
meld techniques from various fields of physics—like quantum information and
analog gravity—in order to produce something novel, or 'cute,' as he liked
to say."
"The Hawking process is one of the richest physical phenomena connecting
seemingly unrelated fields of physics from the quantum theory to
thermodynamics and relativity," said Dimitrios Kranas, LSU graduate student.
"Analog black holes came to add an extra flavor to the effect providing us,
at the same time, with the exciting possibility of testing it in the
laboratory. Our detailed numerical analysis allows us to probe new features
of the Hawking process, helping us understand better the similarities and
differences between astrophysical and analog black holes."
Reference:
Ivan Agullo et al, Quantum Aspects of Stimulated Hawking Radiation in an
Optical Analog White-Black Hole Pair, Physical Review Letters (2022).
DOI: 10.1103/PhysRevLett.128.091301
Tags:
Physics