Scientists at Chalmers University of Technology have succeeded in creating light from vacuum.
Counterintuitively, vacuum isn’t really empty: it’s full of various particles that are continuously popping in and out of existence. Since their existence is so brief, they’re usually referred to as virtual particles.
Back in the 1970s, it was predicted that it should be possible to persuade photons to leave their virtual state and become real ones – in other words, measurable light – if they were allowed to bounce off a mirror moving almost as fast as the speed of light.
And now, this phenomenon, known as the dynamical Casimir effect, has been observed for the first time.
“Since it’s not possible to get a mirror to move fast enough, we’ve developed another method for achieving the same effect,” says Per Delsing, professor of experimental physics at Chalmers.
“Instead of varying the physical distance to a mirror, we’ve varied the electrical distance to an electrical short circuit that acts as a mirror for microwaves.”
The ‘mirror’ consists of a quantum electronic component referred to as a superconducting quantum interference device, which is extremely sensitive to magnetic fields. By changing the direction of the magnetic field several billions of times a second, the scientists were able to make the ‘mirror’ vibrate at a quarter the speed of light.
“The result was that photons appeared in pairs from the vacuum, which we were able to measure in the form of microwave radiation,” says Per Delsing. “We were also able to establish that the radiation had precisely the same properties that quantum theory says it should have when photons appear in pairs in this way.”
What’s going on is that the ‘mirror’ transfers some of its kinetic energy to the virtual photons, helping them to materialise.
“Relatively little energy is therefore required in order to excite them out of their virtual state,” says associate professor of theoretical physics Göran Johansson.
“In principle, one could also create other particles from vacuum, such as electrons or protons, but that would require a lot more energy.”