Scientists are getting closer to being able to spot Hawking radiation – that elusive thermal radiation thought to be produced by the event horizon of a black hole. However, it is difficult to understand the concept of this radiation, let alone find it.
A new proposal suggests creating a special type of quantum circuit to act like a “black hole laser”, essentially simulating some of the properties of a black hole. Like with previous studies, the idea is that experts can observe and study Hawking radiation without really having to watch real black holes.
The basic principle is relatively simple. Black holes are objects that distort space-time so much that not even a wave of light can escape from them. Swap space-time for another material (like water) and sink it fast enough that the waves going through it are too slow to escape, and you’ve got a pretty rudimentary pattern.
Many examples can also include a “white hole” equivalent – a sort of backward black hole where waves can only escape, but cannot enter.
In this new attempt to design one, the researchers propose to use a material with a structure not found in nature, designed so that the particles it contains can move faster than the light passing through it.
“The metamaterial element allows Hawking’s radiation to go back and forth between horizons”, says physicist Haruna Katayama from Hiroshima University in Japan.
The goal is to amplify Hawking’s radiation enough so that it can be measured, and to achieve this, Katayama also uses the so-called Josephson effect – a phenomenon where a continuous flow of current is created which does not require any voltage.
With the use of the metamaterial and the help of the Josephson effect, this proposal promises to go beyond previous attempts to theorize what a black hole laser might look like, although in fact it hasn’t been done yet.
Such a circuit could potentially produce what is called a soliton, suggests the research – a localized, self-reinforcing waveform that is able to maintain its speed and shape until the system is broken down by external factors.
“Unlike the black hole lasers offered previously, our version has a black hole / white hole cavity formed in a single soliton, where Hawking’s radiation is emitted outside the soliton so that we can assess it,” said Katayama.
Ultimately, the system would mathematically measure a quantum correlation between two particles – one inside and one outside the event horizon, without having to observe them simultaneously.
And this is how Hawking’s radiation is believed to be produced, in the form of pairs of entangled particles. Its discovery would bring us closer to a unified and circular system theory of everything, linking quantum mechanics and general relativity.
Challenges remain to make this black hole laser a reality, but if scientists are able to configure it correctly, it could not only allow us to observe Hawking’s radiation, but also give us the tools to control it, thus opening up a whole series of new possibilities.
“In the future, we would like to develop this system of quantum communication between distinct space-times using Hawking radiation”, said Katayama.
The research was published in Scientific reports.