Science

Scientists create real photons from virtual ones

Scientists create real photons...
Virtual photons bounce off a "mirror" that vibrates at almost the speed of light. The round mirror in the picture is a symbol, and under that is the quantum electronic component (referred to as a SQUID), which acts as a mirror. This makes real photons appear (in pairs) in vacuum. (Illustration: Philip Krantz, Chalmers)
Virtual photons bounce off a "mirror" that vibrates at almost the speed of light. The round mirror in the picture is a symbol, and under that is the quantum electronic component (referred to as a SQUID), which acts as a mirror. This makes real photons appear (in pairs) in vacuum. (Illustration: Philip Krantz, Chalmers)
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Virtual photons bounce off a "mirror" that vibrates at almost the speed of light. The round mirror in the picture is a symbol, and under that is the quantum electronic component (referred to as a SQUID), which acts as a mirror. This makes real photons appear (in pairs) in vacuum. (Illustration: Philip Krantz, Chalmers)
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Virtual photons bounce off a "mirror" that vibrates at almost the speed of light. The round mirror in the picture is a symbol, and under that is the quantum electronic component (referred to as a SQUID), which acts as a mirror. This makes real photons appear (in pairs) in vacuum. (Illustration: Philip Krantz, Chalmers)

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.

Source: Chalmers University of Technology

18 comments
inno
Near lightspeed infinite fuel source for interstellar travel?
austint
Light -- out of nothing? Out of sweet sod-all? Brain boggling. But... This is perhaps the Friday morning coffee talking here, so the Utter Bollix Filter should be quickly applied -- how much electricity did it take to power the magnetic fields? And could we harvest the resulting light to sufficiently re-power the magnetic fields to repeat the process? Which could then create more light ... which could then, you know, blah blah blah, to effectively/potentially create ... ... a perpetual power generation machine? Think of it, free power ... and all of it ours! Ours! Damn, this coffee buzz is fading. Reality intrudes once more. Back to work.
Kostas Pappas
austint, And if we could use dark energy instead of electricity to power the magnetic fields? (as apparently the Universe does...or did it once). Really can we create or trap dark energy?
Carlos Marron
What are the potential applications of this achievement? This is incredible. The foundations of the universe. Wow...
kalqlate
@inno - Nope. Your entire system would be moving at the speed of light, so the effective relative velocity of your mirror or electric field would be 0. Any faster, as in the experiment discussed in the article, would require sufficient energy to be input into the system thus nullifying the energy created by this effect. However, I can imagine uses in quantum computers and communication as the article suggests. @austint - Haha... yes, back to work. Interesting idea though. To do that, the efficiency of your energy recapture system would have to be greater than 100%. Currently, mass-produced solar panels have an efficiency of 6% to 20% whereas the best efficiency achieved in labs is currently 40%. Perhaps we\'ll achieve 100% efficiency someday, but never more than 100%. And, certainly, the energy required to generate the effect would, of course, keep it from being perpetual. In fact, I think your net would always be negative because the energy put into the system will always be greater than what you could get out.
Izzey
A perfect vacuum is impossible to achieve, at least in \'practice\' (theoretically anything is possible)
neutrino23
This is not a source of free energy. I don\'t know the exact mechanism but I suspect that the momentum of the mirror is converted to the energy needed to realize the photons. By definition a mirror is something that interacts with electric fields (the electric fields of the photons interacting with the loosely bound electrons in the mirror is what creates the mirror effect). Therefore, I would think that there would be some inertia effect in moving the electrons that would result in a sort of push back so that the momentum of the mirror convert into making the virtual photons real. This is a classical argument. I don\'t know the quantum equivalent.
YukonJack
Heavy stuff. Will life ever be the same now?
Gregg Eshelman
Step One or perhaps One Point Five towards a Star Trek style transporter? Look really closely at the image and you can see a tiny light tank driven by a tiny Jeff Bridges saying \"Can we merge with this memory, BIT?\" ;)
Anumakonda Jagadeesh
Great Achievement.