Scientists are getting closer to being able to detect Hawking radiation – that elusive thermal radiation thought to be produced by the horizon of black hole events. Just understanding the concept of this radiation is difficult but, let alone finding it.
A new proposal suggests creating a special type of quantum circuit to act as a ‘black hole laser’, essentially simulating some of the properties of a black hole. As in previous studies, the idea is that experts can observe and study Hawking radiation without having to look at any real black holes.
The basic principle is relatively simple. Black holes are objects that distort space so much, not even a wave of light can escape. Change the space to some other material (like water) and make it circulate fast enough so that the waves passing through it are too slow to escape, and you have a pretty rudimentary pattern.
Many examples may also include the equivalent of a ‘white hole’ – a type of black back hole where waves can only escape, but cannot enter.
In this newest attempt to design one, the researchers propose to use a material with a structure not found in nature, one made so that the particles inside it can move faster than the light that passes through it.
“The metamaterial element makes it possible for Hawking radiation to travel back and forth between horizons,” says physicist Haruna Katayama from Hiroshima University in Japan.
The goal is to magnify Hawking radiation enough to measure it, and to achieve this Katayama is also using the so-called Josephson effect – a phenomenon where a continuous flow of current is created that requires no voltage.
Using metamaterial and the help of the Josephson effect, this proposal promises to go beyond previous attempts to theorize how a black hole laser might look, even if in fact the placement of a one together has yet to be done.
Such a circuit could potentially produce what is known as a soliton, research suggests – a localized, self-reinforcing waveform capable of maintaining its speed and shape until the system breaks down by external factors.
“Unlike the previously proposed black hole lasers, our version has a black hole / white hole cavity formed in a single soliton, where Hawking radiation is emitted outside the soliton so we can evaluate it,” says Katayama.
Ultimately the system allows a quantum correlation between two particles – one inside and one outside the event horizon – to be measured mathematically, without having to observe them both at the same time.
And so it is believed that Hawking radiation is produced, as entangled pairs of particles. Its discovery brings us closer to a unified and circular 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 can not only allow us to observe Hawking radiation – it can give us the tools to control it as well, and opens up a whole host of possibilities.
“In the future, we would like to develop this system for quantum communication between distinct time spaces using Hawking radiation,” says Katayama.
The research was published in 2007 Scientific Reports.