Last night there was a very interesting NOVA episode on PBS. Part of it dealt with an experiment one guy did, where he split a beam of light into two beams. The first beam went through the air to a detector, the second was blocked by a barrier of some kind.
The unobstructed beam reached the detector at the speed of light. The obstructed beam, however, reached the detector faster than the speed of light. This is from the effect of quantum tunneling. I won’t try to explain that here, since I will likely not be able to explain it accurately. But I think I have a passable idea of how it works.
After showing the scientist who performed this experiment, they cut to a different scientist (playing a piano, for those who saw this episode), and although he agreed with the seemingly well-established quantum-tunneling FTL effect, he denied that it could carry information.
Then, they went back to the original scientist, who played an audio tape made from the quantum-tunneled beam of light. It was scratchy, but it was very clearly music (Mozart, if I remember properly).
They didn’t go back to the piano player like I hoped (unless I missed it somehow), but by what possible reasoning could someone argue that that was not information?
Well, music would definitely be information. I don’t know the details of that experiment, but I would assume that the measurements that allowed the music to be interpreted were limited in such a way that the music couldn’t actually be read FTL.
I know I’m not going to get this exactly right but it might jump start someone who’s more current than I am –
There is a school of quantum mechanical thought that suggests it might be possible to transmit information FTL because of phase relationships between associated particles. It goes something like this: 1) Start with two particles of unknown orientation but known relationship – if one is up, the other must be down. 2) Separate the two particles (in some special manner so the phase relationship is maintained). 3) Perform an experiment that demonstrates the orientation of one of the particles. And, voila!, you instantaneously know the orientation of the other particle.
(Please don’t bother with the errors in my summary – I know it’s flawed, I was just trying to bring out the general idea.)
I suggest a web search on “Bell’s Theorem” or “EPR Paradox” for more info.
BTW, music certainly contains information, so if you can transmit music you’ve proved your point. I think the burden of proof in this case is to prove that you transmitted it FTL. I don’t think my ears could tell the difference!
I wonder if although it might be impossible to establish a data link between two points at greater than light speeds, whether you could have a link that transfers information faster than light once the transmitting and receiving points have been emmeshed with each other.
If you could transfer information at any time in any way so that it could be interpreted FTL, the doors to causality violation are opened. I think these recent experiments are a good illustration of the fundamental security of causality. Even the wierdest things that QM can throw still don’t hurt it.
I don’t think there would be causality problem with quantum tunneling FTL, since there isn’t really anything traveling at a velocity greater than light, at any one time. As I understand it, the particle essentially “magically” disappears from one point, and appears at another without traveling through the points in between.
Undead Dude, I’m assuming the causality issue you bring up is related to something traveling faster than C, and going back in time. I don’t think this would apply to quantum tunneling. Is that the issue you meant, or are there other causality problems that might come up?
Information travelling FTL in one reference frame will be information travelling back in time from someone else’s reference frame. It is the same whether it is an object moving, or information just appearing in a new place.
So yes, causality will still be an issue for an FTL transmission of information regardless of the method. Fortunately, each QM FTL trick that has come down the pike has very specifically been unable to translate information FTL. I don’t think that’s a coincidence. I think it is a hint that the universe is well designed.
If I may add my 2 bits. I have yet to see an experiment claiming to prove EPR with Bell’s Inequality, that didn’t raise serious questions about the validity of the testing methods. Usually, they make the mistake of saying “And if we had continued the experiment with setup X, we would have gotten different results than we did running setup Y.” The problem is, in a random system, you can’t correctly make those assumptions, especially where Heisenberg’s Uncertainty comes into play with each new setup.
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I don’t have a cite, but the last experiment that I’m aware of which showed any promise at all was begun about 5 years ago.
Silver atoms, which were at one time in contact with one another, were divided into two batches. One batch was kept in the US, while the other was shipped to the UK.
They would “do stuff” to one batch, while measuring the other batch for changes.
Last I heard about it was in one of the science 'zines, but something seemed to be happening.
Revtim, I’m no expert on this (this may become obvious as you read on,) but I read an article about an experiment like this about a year ago. The way I read it, one of the explanations was that the leading edge of the packet of light made it through before the material ‘knew’ to block the light. Since the trailing edge of the packet was absorbed, the light that made it through appeared to travel at above the speed of light.
I’m reviving this thread on the off-chance that new members might have something to add, because I’m still wondering about the experiment in the OP.
Note that the EPR “spooky action at a distance” effect is not involved, so it would be helpful if we stuck to the quantum tunneling that seems to be enabling this apparent FTL data transmission.
Undead Dude, if you’re still around, you brought up some good points, but I still don’t see the flaw in the original experiment. I realize that you don’t know the details of the experiment, but do you have a quess what “trick” there might be in the quantum tunneling method that is preventing FTL data transmission?
Revtim, do you happen to know the name of the scientist who claims to have transmitted information faster than light? (A reference would of course be ideal, but I could search myself if you have a name…)
I haven’t heard of this experiment, so I can’t comment on it specifically. But I’ll bet you dollars to donuts that information was not transmitted faster than light. If you can help me find the specifics of the experiment, I’ll try to give a detailed answer.
Ugh. I wish I could get search to work from here, because there was a very recent thread on this here. (Within the last month, even the last few weeks, called, I believe, “Gunther [last name forgotten] and his amazing [something or other].” Not very helpful, I’m sure.)
I don’t remember the conclusions, as I don’t know the setup, but I’ll second Giraffe in saying that information was not transferred FTL.
Good News! I found the name the guy: Guenther Nimtz.
The Nova episode:
“Time Travel”. Kip Thorne, author of “Black Holes and Time Warps : Einstein’s Outrageous Legacy”, discusses and illustrates worm holes - the way back in time. This video features excellent video depictions of time travel and includes interviews with Carl Sagan, John Wheeler, Richard Keating, Joe Hafele, Matt Visser, Steven Lamoreaus, Igor Novikov, Guenther Nimtz, Raymond Chiao, David Deutsch and Ken Ziet. The program was broadcast on PBS on October 12, 1999.
This link will answer your questions about faster than light information transfer via tunneling (not). I was going to excerpt from it, but I couldn’t figure out how to do it and keep it clear. So click on it or continue to wallow in hopeless ignorance. http://www.socorro.demon.co.uk/gunter.htm
