Quantum Computing Applications With Black-hole Lasers.
A soliton (top) performing the function of a mirrored laser cavity (bottom).
Haruna Katayama of Hiroshima University in Japan has developed an electromagnetic counterpart for a black hole laser - a technology that could possibly enhance Hawking radiation from a black hole's event horizon and make it detectable.
The concept stems from parallels shown with Bose-Einstein condensates, and it has the potential to provide fresh light on the link between quantum mechanics and gravity.
The gadget, if created, may potentially progress technologies like quantum computing.
When the two fundamental foundations of current theoretical physics – general relativity and quantum mechanics – collide, Hawking radiation is one of the few potentially observable predictions.
Quantum theory predicts the formation of photon pairs near a black hole's event horizon.
One of the photons with negative energy enters the black hole and vanishes.
The other, who has good energy, flees into space.
This phenomenon would allow black holes to emit radiation, giving them a temperature that could be measured - potentially revolutionary since it would imply they possessed internal degrees of freedom.
Unfortunately, all known black holes would have temperatures lower than the cosmic microwave background.
The produced radiation would be obscured by the absorbed radiation, making it unobservable.
However, in 1981, William Unruh of the University of British Columbia in Canada demonstrated that multiple physical systems are mathematically similar to the one that generates Hawking radiation, allowing the phenomenon to be explored in the lab.
Water waves, fiber-optic systems, and Bose-Einstein condensates are examples of analogies.
"[These analogies] aren't going to go to the core of any quantum gravity topic since that's outside the regime one is examining here," says theoretical physicist Miles Blencowe of Dartmouth College in the United States, "but there are still serious concerns with Hawking's calculation." These analogues may be compared to quantum simulators in several ways."
Different "analogue gravity" systems have raced to deliver the first proof of Hawking's numerous predictions, and claims made by one group have often been challenged by others.
Katayama claims in the new paper that one of Hawking's most intriguing predictions, made in 1999 by Steven Corley of the University of Alberta in Canada and Ted Jacobsen of the University of Maryland in the United States, may be tested in a superconducting electric circuit.
The pair described how a black hole laser works, which necessitates the presence of a "white hole" inside the black hole.
Negative energy photons are reflected back towards the black hole horizon by the white hole's inner horizon, where they are unable to escape and are reflected back.
As photons bounce across horizons, their energy becomes more negative, forcing the energy of photons sent into space to become increasingly positive.
"One of these is exceedingly unlikely to be realized in nature," Blencowe argues, "but it is conceivable to produce them in analogies."
In a Bose-Einstein condensate, the first such black hole mimic was created in 2016.
Katuyama suggests utilizing the Josephson phenomenon, which enables a superconducting current to become quantized, to generate a non-dispersive wavepacket termed a soliton in a metamaterial resonator, with radiation in the soliton becoming quantum-mechanically entangled with radiation emitted from the soliton.
Hawking radiation is the equivalent of this released radiation.
"Unfortunately, at this time, we have not been able to offer recommendations with this system that outperform other [analogue] systems," Katuyama adds.
"However, the suggested superconducting quantum device has shown the dynamic Casimir effect, which is the dynamic fluctuation of the vacuum, and the photon detecting technology established in this system is a tremendous advantage that cannot be reproduced by other systems."
Furthermore, since it is based on nanotechnology, this system is very controllable.
As a result, by manipulating the circuit settings, we can move the black hole from the classical to the quantum domain, allowing us to investigate the quantum pair production of black holes and white holes from a vacuum."
“Systems very close to this have been realized: they're very important as very sensitive detectors of microwave photons and they're very important in superconducting quantum bits,” says Blencowe;
“If the proposals are realized, it would be a very clean demonstration of the Hawking effect – the signal is relatively large.”
He also sees a lot of potential for technology transfer:
"Quantum computing is all about creating entanglement as a resource," he says, "so entangled microwave photons created via these sorts of technologies might be quite valuable."
