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Scientists create real photons from virtual ones


December 1, 2011

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)

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


Near lightspeed infinite fuel source for interstellar travel?


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.


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.



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?

Kostas Pappas

Heavy stuff. Will life ever be the same now?


What are the potential applications of this achievement? This is incredible. The foundations of the universe. Wow...

Carlos Marron

@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.


A perfect vacuum is impossible to achieve, at least in \'practice\' (theoretically anything is possible)


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?\" ;)

Gregg Eshelman

Great Achievement.

Anumakonda Jagadeesh

if perfect vacuum isn\'t possible, then definitely there will be particles. This experiment just proves the very first statement. On the other hand, if the remaining particles can now be detected, one day they could be captured, thus a better vacuum could be created, if that\'s the goal. This will help in better, more powerful miniaturized devices.

Dawar Saify

A question; so if you can make a mirror or likewise, vibrate at almost the speed of light right. Wouldn´t it then be possible to \"move\" the vibration slightly in one direction, meaning; the vibration consist of moving in 2 or more directions: so if you made it move slightly more to one side than the other in the vibration, with every move:

Wouldn´t that mean we would be able to \"vibrate\"-travel at nearly the speed of light?

Random chaotic thought Christoffer Christoffer Sperling

Some commentator do not understand that we can not extract pure energy from nothing! When we get light from vacuum we also spend much more energy for moving that mirrors.

Pavel Chernov

If we can\'t extract pure energy from nothing, then where did the universe come from?


In physics it is understood that something cannot be created from nothing. Science is based on observation; these observations check the science every time an observation is made thus as soon as the observation is wrong then the science must also be wrong.

Realize that we are here, from nothing. We apparently just popped into existence. Thus this blatant observation should discredit the science that something cannot be created from nothing as, we are here.

Has any lay considered the implications of E=MC2? This equation is essentially F=MA

Velocity squared is acceleration, unless I am mistaken. Thus this would imply that if E=MC2 then everything is travelling at the relative speed of light.

If you could imagine, sitting outside of our universe watching the big bang all the debris propelled by infinite energy would be travelling at the speed of light. hence the expanding universe. Thus we shouldn\'t try to prove matter cant travel at the speed of light, because we already are.

Or I am just completely wrong on all counts!


someone mention a cat?

Hilary Albutt

Well, I am sitting here emitting vast gobs of light. Infrared light. If you looked at me with a camera sensitive to the infrared spectrum, I would look quite bright indeed. So, if objects emit light depending on their temperature (think of some steel thing heated up to \"red heat\", or else think of a light bulb filament heated up \"white hot\") then how could you tell if the light is being interrupted out of virtual Casimir photons by a SQUID vibrating at 1/4 the speed of light? That SQUID might get a bit hot at that frequency and could be emitting the photons from its own self.


Nice idea. Kind of ridiculous that I had to learn about it from the Big Bang Theory. But whatever.

I find the real/virtual nomenclature unfortunate. Photons are photons. They all exist, the difference is whether they can be observed, which depends on whether they are involved in elastic or inelastic collisions.

'Virtual' photons are involved in elastic collisions that conserve energy.

'Real' photons are inelastic - in order to be observed, they have to do work on an observer, and so they they lose energy to the observer.

Got it? Good. So now you see how 'virtual' photons can collide elastically with a mirror, so long as the mirror is moving fast enough to strike them...

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