German Scientists Break Speed of Light

[Jason]

Thought this would be of interest:

Breaking Light Speed?

[Broomstick]

Results need to be confirmed by independent group before it's official - but I eagerly await such a repeat.

[Turin]

Quote the article!

A pair of German physicists claim to have broken the speed of light - an achievement that would undermine our entire understanding of space and time.

According to Einstein's special theory of relativity, it would require an infinite amount of energy to propel an object at more than 186,000 miles per second.

However, Dr Gunter Nimtz and Dr Alfons Stahlhofen, of the University of Koblenz, say they may have breached a key tenet of that theory.

The pair say they have conducted an experiment in which microwave photons - energetic packets of light - travelled "instantaneously" between a pair of prisms that had been moved up to 3ft apart.

Being able to travel faster than the speed of light would lead to a wide variety of bizarre consequences.
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For instance, an astronaut moving faster than it would theoretically arrive at a destination before leaving.

The scientists were investigating a phenomenon called quantum tunnelling, which allows sub-atomic particles to break apparently unbreakable laws.

Dr Nimtz told New Scientist magazine: "For the time being, this is the only violation of special relativity that I know of."

Worst. Science Article. Ever.

That pretty much told us nothing. It sort of sounds like the "quantum teleporting" stuff we've heard about previously, but who's to say. I'd like to see where they're publishing this work.

[Colonel Olrik]

Worst. Science Article. Ever. That pretty much told us nothing.

That's the news.

This is a science article:

On Superluminal Photonic Tunnelling, Springer published 2007

Günter Nimtz3, Astrid Haibel3 and Alfons A. Stahlhofen4
(3) II. Physikalisches Institut, Universität zu Köln, 50937 Köln, Germany
(4) Institut für Physik, Universität Koblenz, 56075 Koblenz, Germany

Evanescent modes or the tunnelling process are characterized by an imaginary wave number. These special solutions of the Helmholtz and of the Schrödinger equations first noticed in connection with the total reflection were said to have no physical meaning about 200 years ago. Last century the tunnelling problem in quantum mechanics has been described by the phase time approach. The phase time approach yields the group velocity of a wave packet (see e.g. Hartman, 1962). Nowadays the phase time approach is used in network analyzers to determine the group velocity of an electromagnetic wave in devices.
We have reported about superluminal signal velocities in photonic tunnelling. It was observed that the superluminal photonic tunnelling time data measured in the time domain are in agreement with the calculated phase time data. This result is also in agreement with the definition of the barrier transition time given in the Federal Standard 1037 C (NTIA, USA 2000). Thus we have added further credibility to the assumption that the photonic tunnelling results are representative for quantum mechanical tunnelling of particles.

IThey have articles published in I3E, Springer and the usual suspects, they're not hard to find.

[Glass Pearl Player]

The publication as PDF-file
Yes, it is the same Professor Nimtz that claimed to transmit Mozart faster than light. It's a slightly different experiment this time. To me, the article looks sound. If I understood correctly, evanescent waves[1] can be viewed as virtual photons that cannot be observed directly and don't square up with Einstein: If one would take the equations at face value, they would have negative energy not unlike tachyons.

[1] Evanescent waves appear when one tries to analyze total reflection; they are needed to make the solutions continuous, but they have a purely imaginary "frequency".

[Fingolfin_Noldor]

Give the paper no. on arXiv. The link does not work.

[Feil]

Pardon my ignorance, but how would you know the difference between c and anything faster over such a short distance? Do they have time pieces with resolutions on the order of than 1E-9 seconds?

Too, have they actually transmitted any information? If not, who* gives a fuck?


*beyond people interested in the study of evanescent waves

[Fingolfin_Noldor]

Pardon my ignorance, but how would you know the difference between c and anything faster over such a short distance? Do they have time pieces with resolutions on the order of than 1E-9 seconds?

Too, have they actually transmitted any information? If not, who* gives a fuck?


*beyond people interested in the study of evanescent waves

An experiment of this variety is likely a series of lens that focus a laser beam onto an obstacle or whatever they wish to use as a barrier, with a photomultiplier tube or a CCD camera, whichever gives the better resolution and quantum efficiency. They would of course have to do this in a dark room and with the necessary stop watch apparatus, preferably with the CCD connected to the computer and timing the occurrence of the photon reaching the CCD.

However, Quantum Tunneling is intrinsically "faster than the speed of light" since it is instantaneous.

As for its worth, I guess it potentially might have use in Quantum Cryptography or something else in Atomic Molecular Optics.

[Molyneux]

If they've actually transmitted information faster than light, or better yet, actual energy...I don't think it's unrealistic to say this would be the most important bit of research done this year.

[Turin]

Worst. Science Article. Ever. That pretty much told us nothing.

That's the news.

This is a science article: <snip>

Uh... ok. Any lurking creationists or other similar idiots take careful note about what I'm about to say:

"Zounds. This is a subject that is clearly too far outside my education to have any real understanding of. Perhaps I can hope to expand my horizons somewhat if I see an article on it for bright laypersons in Scientific American or something. But obviously this is subject material for the experts and I have no ability to meaningfully contribute to its discussion."

[Glass Pearl Player]

Article Number at arXiv is 0708.0681
http://arxiv.org/abs/0708.0681
http://arxiv.org/ftp/arxiv/papers/0708/0708.0681.pdf (Note no trailing slash. Sorry for the inconvenience)

If they've actually transmitted information faster than light, or better yet, actual energy...

I think that would be the same - can one transmit information without using energy?

Zounds. This is a subject that is clearly too far outside my education to have any real understanding of.

Me too. I stopped studying physics during the introduction to quantum and solid state physics some time ago, I'd have to reread quite an amount till I can formulate coherent questions on that topic again .

[Sea Skimmer]

I hope they’ve got insurance that covers that kind of damage

[Starglider]

Do they have time pieces with resolutions on the order of than 1E-9 seconds?

Yes. Multi-gigahertz oscilliscopes that let you examine minute time differences between different signal trains are relatively common - they're necessary to design and debug modern high-speed interconnects. Scientific applications can easily use timers based on atomic clocks - which have a frequency of around seven or nine gigahertz (depending on type) before frequency multiplication.

Too, have they actually transmitted any information? If not, who* gives a fuck?

Yes, that is the key question, which for some reason the summaries don't give a clear answer to.

[phongn]

ArsTechnica has a brief article on the issue that helps explain things:

A paper submitted to the physics arXiv has been picked up by a number of major news outlets (e.g., the Daily Mail) because the paper suggests that its authors have measured something traveling faster than the speed of light. Unfortunately, the claim is worse than weak; it is silly. I'll talk about why that is after briefly discussing their research.

The paper in question has no data at all so; although it asserts that it has measured superluminal velocities, it offers nothing to back that up. It also has very little in the way of experimental detail, so we can't determine with certainty what they are measuring, making it very difficult to evaluate their claims. We'll take as close a look as we can, given these limitations.

The researchers make use of the property called total internal reflection (brief discussion). When light is above a certain angle of incidence on an interface between two materials—say, at the face of a prism—it can be totally reflected, provided it is arriving at this interface from the higher refractive index material. However, near the boundary, something called an evanescent wave forms that does not propagate like normal light (technically it does not propagate at all) and quickly decays away to nothing. If you take a second prism and place it very close to the interface where total internal reflection occurred, then some light from this evanescent wave will leak across the interface and exit the second prism. The prisms have to be no further than the wavelength of light involved for this to work.

Now the interesting questions are: where did the energy in this light come from? How fast did it travel across the boundary? The first question is interesting because the evanescent field has no energy in it. This is because the electric and magnetic fields that make up the field are phased in such a way that the product is always zero. The second question is interesting because the speed of light is not defined in a way that is intuitive to non-physicists. Suffice it to say that, for the evanescent wave, the speed of light is zero, and therefore any measurable speed is faster than the speed of light.

So, how are these authors measuring an excessive speed of light? In practical terms, most experiments measure light in terms of what is called the group velocity, which is how fast a pulse propagates along an underlying carrier frequency. This can, in some circumstances, lead to the pulses traveling faster than the speed of light in the medium they're in, but not faster than light in vacuum. Although the setup in the new paper is not entirely clear, they were measuring the arrival time of pulses, which means we're talking about group velocity rather than the actual speed of light.

Another problem that occurs in these experiments comes from determining when the pulse actually arrived. If you analyze a pulse of light, you find that it is made up of a huge number of frequencies that, as you move away from the fundamental frequency, get lower and lower in amplitude. Once you look at the experimental set up in detail, you find that it is triggering on the pre-pulse noise generated by these high frequency components.

Separate from the whole speed of light issue, the answer to the energy question in this experimental setup is interesting. Once the two prisms are close to each other, the evanescent wave is partially reflected from the second prism back to the first prism. When this happens, the total electric field and total magnetic field are no longer such that their product is always zero—there is energy in the field. Furthermore, if you analyze the components of the fields that contain the energy, you find that they do have a non-zero speed of light and it is—you guessed it—the same c that applies everywhere else in the universe.

So although this makes for an interesting physics lecture—or at least I thought it was interesting—it is not new physics and not a breakdown of special relativity.

[Tahlan]

Thanks for the ars technica link, and the article. I thought the claim of breaking the speed of light was less than genuine, but for the wrong reasons.