Scientists create real photons from virtual ones
By Bryan Clark
December 1, 2011
A perfect vacuum is impossible to achieve, at least in theory. As anyone with any interest in quantum physics would know, the vacuum is full of various particles that fluctuate in and out of existence. These "virtual" particles have been the focus of scientist, Christopher Wilson. Working with his team at Sweden's Chalmers University of Technology, Wilson has succeeded in producing real photons from these virtual photons. Which, in layman's terms, means that they have created measurable light ... from nothing.
Creating light from nothing is not a new idea - in fact it dates back to 1970 when esteemed physicist Gerald Moore predicted the possibility. It is, however, the first time it has been observed.
The effect is known as the Casimir effect. The static Casimir effect can be demonstrated by placing two mirrors both parallel and close together. If the gap is smaller than the wavelength of the virtual particles you can expect to see the mirrors push together as the virtual particles are excluded. We know this to be true, and it has been seen before.
The dynamic Casimir effect is trickier as it involves moving said mirrors through space at relativistic speeds. At slower speeds it is easy enough for the virtual particles to adapt and remain paired until they disappear. At high speeds, however, the pairs are separated and therefore do not entirely disappear, instead they become real photons and cause the mirror to shine a light.
Until now the problem has always been getting the mirror to move fast enough to produce the required effect. When I say fast, I mean percentages of the speed of light fast.
"Since it's not possible to get a mirror to move fast enough, we've developed another method for achieving the same effect," explains 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."
To achieve this the delightfully named SQUID (Superconducting quantum interference device) was used. Powered by magnetic fields over a mere 100 micrometers, the device was able to produce enough speed to travel 1/4th the speed of light over a nanometer in distance.
Scientists aren't quite clear what to make of the findings so far, but it is expected they'll be of particular interest to those in the quantum information research field, which includes the development of quantum computers.