Virtual photons become real in a vacuum

Ashley N. Rice, ashley.rice@photonics.com

By changing the position of a mirror inside a vacuum, virtual particles can be transformed into real photons that can be experimentally observed.

In a vacuum, there is energy and noise, the existence of which follows the uncertainty principle in quantum mechanics. These virtual particles in the vacuum can momentarily appear and disappear, and can be converted into detectable light particles.

Now, researchers at Aalto University and the VTT Technical Research Center of Finland have shown that vacuums have properties not previously seen. They demonstrated that by changing the position of the mirror in a vacuum, virtual photons can be transformed into real ones.

“If we act fast enough, we can prevent the particles from recombining – they will then be transformed into real particles that can be detected,” said Dr. Sorin Paraoanu of Aalto.

Optical microscope image of the chain of SQUID of the metamaterial sample in which the dynamical Casimir effect was studied. The speed of light in this material could be varied by changing the magnetic field through the SQUID loops.

An array of superconducting quantum-interference devices (SQUID) – parts resembling devices used in imaging small magnetic fields in the brain – were used in the experiment. By changing the magnetic field, the speed of light in the device can be altered. Radiation reflecting from such a device experiences it as a moving mirror from the standpoint of the vacuum’s electromagnetic field. “By quickly varying the speed of light in the array, we can extract microwave photons out of the vacuum’s quantum noise,” said Aalto doctoral student Pasi Lähteenmäki.

These devices could be used to create an artificial event horizon as well as to observe Hawking radiation emanating from it. It could also help cosmologists to better understand how the universe was formed and to advance the development of quantum computers.

The study was published in the Proceedings of the National Academy of Sciences (doi: 10.1073/pnas.1212705110).