FTL signaling via frustrated total internal reflection

[Turtle]

Saw this today and thought you all would find it intersting. :hihi: >>

 

Future fibre networks to exceed light speed? - ZDNet UK

 

...Exceeding the speed of light, approximately 300,000km per second, is supposed to be completely impossible. According to Einstein's special theory of relativity, it would take an infinite amount of energy to accelerate an object through the light barrier.

 

But two German physicists claim to have forced light to overcome its own speed limit using the strange phenomenon known as "quantum tunnelling". ...

[CraigD]

Saw this today and thought you all would find it intersting. ;) >>

 

Future fibre networks to exceed light speed? - ZDNet UK

C1ay posted 12558 on the same story yesterday afternoon. The ZD article Turtle links is, IMHO, better than the telegraph.co.uk article in the news thread.

 

At first glance, I’m surprised that knowledgeable professional scientists would claim that the effect described is “the only violation of special relativity that I know of”, or believe that it could be used for a faster-than-light communication device. Quantum physics contains may examples of “superluminal effect at a distance”, but none that can be exploited to practically send a signal (or a physical object) to a distant point at greater than the speed of light in vacuum. At second glance, the cynic in me suggests that this is most likely a publicity stunt to draw attention – and, hopefully, additional research funding – to these scientists. In the practical world of limited-funding science, I can’t fault them for that.

[alexander]

Two German scientists (Gunter Nimitz and Alfons Stahlhofen) just proved that through photon tunneling, you can accelerate photons to move faster then the speed of light. Actually they just demonstrated this with 2 prisms about a meter apart shining light on the same detector, now even though they are not equidistant from the surface, the photons from both lenses were shown to hit the surface at the same time.

 

I may be wrong ofcourse, since i dont have time to find more evidence, all i have to go by is a Russian newspaper article dated Aug 17th and a wiki article titled Faster-than-light

[Jay-qu]

Two German scientists (Gunter Nimitz and Alfons Stahlhofen) just proved that through photon tunneling, you can accelerate photons to move faster then the speed of light. Actually they just demonstrated this with 2 prisms about a meter apart shining light on the same detector, now even though they are not equidistant from the surface, the photons from both lenses were shown to hit the surface at the same time.

 

I may be wrong ofcourse, since i dont have time to find more evidence, all i have to go by is a Russian newspaper article dated Aug 17th and a wiki article titled Faster-than-light

Its to this that I was referring, but if this experiment turns out to be correct we have to be careful how we define speed and acceleration in these situations. ie is the photon actually moving FTL or is it just 'transported' across the gap FTL - is there a difference, I would say yes, as there is no possibility of detecting the photon in the intervening gap.

[freeztar]

Its to this that I was referring, but if this experiment turns out to be correct we have to be careful how we define speed and acceleration in these situations. ie is the photon actually moving FTL or is it just 'transported' across the gap FTL - is there a difference, I would say yes, as there is no possibility of detecting the photon in the intervening gap.

 

 

I agree with your thoughts Jay.

 

If it is quantum tunneling based upon quantum uncertainty, then it is safe, imho, to call this effect 'teleportation' rather than FTL travel. Of course, teleportation is not an accurate description as it is more of a probability (from what I gather from the reading material available).

 

Nonetheless, if we measure from our reference frame, some information appearing in a location faster than light speed, then we must agree that FTL travel has transpired, from our frame of reference. This is not in disobeyence of SR as Jay-qu has pointed out, but it speaks volumes for quantum dynamics. It's implications are potentially enormous.

[alexander]

Its to this that I was referring, but if this experiment turns out to be correct we have to be careful how we define speed and acceleration in these situations. ie is the photon actually moving FTL or is it just 'transported' across the gap FTL - is there a difference, I would say yes, as there is no possibility of detecting the photon in the intervening gap.

Right, it seems to change position FTL, but does it actually travel the distance. I see where you are going with this, sort of. Say I'm driving a car at 60 miles an hour (yeah ok), and all of a sudden I instantaneously transport a mile down the road (and according to quantum theory it may very well happen, hence why i am reading and watching more into the string theory). But without having any equipment that detected the car on the road while i was instantaneously traveling that mile there are questions to ask: does this mean that i traveled at infinite speed for that moment, or did i continue to travel at 60mph bu happened to instantaneously relocate to a different coordinate in a space/time fabric, say via something like a worm whole.

Am I on the right track of thinking here? (and i am not a math person, more of a philosophical physics person)

If i am, then we may have to redefine speed to include the concept of body positioning over the distance...

[Jay-qu]

yes alex thats just it, how are we to redefine velocity when things can appear to instantaneously relocate. If is was using a wormhole as the mechanism for relocation I would still think it would take some time, possibly shorter but also possibly longer, because the idea of a wormhole is your still occupying space, just twisted up non-flat regions of it. Which would mean they could also serve as detours, not just short-cuts.

[LaurieAG]

Its to this that I was referring, but if this experiment turns out to be correct we have to be careful how we define speed and acceleration in these situations. ie is the photon actually moving FTL or is it just 'transported' across the gap FTL - is there a difference, I would say yes, as there is no possibility of detecting the photon in the intervening gap.

 

Hello Jay-qu,

 

Has anybody come across an accurate image on how the experiment was setup/undertaken?

 

I had a look at the New Scientist article and their image of the light paths didn't seem right. Their image showed the control beam travelled along the back edge of the first prism for a distance before 'reflecting' off the inside of the first prism, at the mirror of the angle it came in (i.e. was the control photon tunelling as well, because it certainly wasn't reflecting normally).

 

Surely, if the 'tunnelling' photon was going through the prism(s) at the same angle as the control photon and it went across the gap to the second prism, you would expect the control photon to reflect off the front face of the second prism, leaving the actual distances travelled by both photons being much the same.

[Jay-qu]

No, I havent, at the moment Im just enjoying speculating on this slight possibility :eek_big: but I would love to see a published article or experimental setup.

[LaurieAG]

Hi Jay-qu,

 

No, I havent, at the moment Im just enjoying speculating on this slight possibility :eek_big: but I would love to see a published article or experimental setup.

 

I just dug up the following article, they refer to the setup and have some good images/diagrams.

 

Popular Science - Feature

 

Purely imaginary solutions of the wave equation seem to imply a zero shift in the phase of the wave – which would mean that the wave spent zero time in the barrier, crossing it instantaneously (or perhaps more accurately getting from one side of the barrier to the other without crossing the intervening space). With the electromagnetic analogies available, it was tempting to test tunneling time for real using photonic experiments.

 

First microwave [3] and later optical experiments [4,5]were carried out to measure the total tunneling time of the photons.(In Fig.2: the tunneling time is tv+th) This strange, two part timing is due to the nature of frustrated total internal reflection. The photon is not a point, but extends out into the gap, so the reflection appears to take place behind the surface of the first prism, resulting in a shift down the surface before reflection, D in the diagram, called the Goos-Hänchen shift. This shift was conjectured by Newton 300 years ago, but only measured in 1947 by Goos and Hänchen.

 

The small value of the tunneling time results in velocities faster than light – photons crossing the barrier take less time than they should at light speed. In the actual experiment, using microwaves, it was found that both reflected and transmitted beams left their respective prisms at exactly the same time. With the distance d set at 60mm, the microwaves should have taken 20 picoseconds to cross the gap. However this time was not detected. The experiment was accurate to ±5 picoseconds, so something should have shown up. It seems that tunneling inside the barrier is nonlocal, proceeding in zero time. (Details of the experimental set-up are given in [6])

 

It might seem possible that the tunneling photon actually heads straight across the gap and doesn’t first undergo the shift – but the time taken is independent of the gap size and as near as can be identified identical with the time to cover the distance D.

 

Another interesting aspect of the tunneling process is that the predicted energy of the tunneling particles is negative. This fact, often overlooked in photonics, is noted in solid state physics [7], in quantum mechanics [8], and some textbooks on near-field optics. Are tunneling photons detectable? Theory says no, they should only be in evidence outside the barrier – see, for instance [8 and 9]. We have carried out a standard experiment with an undersized waveguide as shown in Fig.1a.

[Jay-qu]

There is much to speculate about, imagine this experiment gets verified and reproduced, a few years down the track there are going to be loads of phenomenon of this instantaneous teleportation and probably still no explanation for it :hihi:

 

every scholar I ask about this at uni is still skeptic and thinks either something has been lost in translation or just plane faked.. :hihi:

 

I want it to be true, I really do, things would be so much more interesting that way - and my hope of travelling to the other end of the galaxy has re-newed hope :D

[CraigD]

There is much to speculate about, imagine this experiment [Nimtz and Stahlhofen “breaking the speed of light” experiment] gets verified and reproduced, a few years down the track there are going to be loads of phenomenon of this instantaneous teleportation and probably still no explanation for it :hihi:

 

every scholar I ask about this at uni is still skeptic and thinks either something has been lost in translation or just plane faked.. :hihi:

As we discussed in the news thread 12558, Nimtz and Stahlhofen’s experiment, while not yet widely (or, to my knowledge, at all) independently reproduced, isn’t inexplicable in conventional quantum physical terms. People are wise, I think, to take it skeptically until and if it is verified, but I’ve no strong doubt that it will not be.

 

The effect is not instantaneous – it only removes some, not all of the travel distance and time of a light signal from its trip. While currently a minute fraction of the total signal travel time measured in the experiment, it should be possible in principle to make the ratio of normal to “tunneled” distance smaller, possible enough to produce an effective signal speed of several times the speed of light in vacuum © – though, for reasons I’ll speculate on shortly, only over short distances.

I want it to be true, I really do, things would be so much more interesting that way - and my hope of travelling to the other end of the galaxy has re-newed hope :lol:

I don’t hold much hope that N & S’s technique can be used for space travel or communication.

 

First, it’s a signaling, not a transportation, phenomenon. Though in principle it should be possible to perform a variation of the experiment with particles other than photons, such as electrons or much more massive protons, increasing their effective speed (which cannot reach, though may be a large fraction of, c) to greater than c, the probabilistic (most of the particles don’t tunnel) nature of the phenomena appears to me to practically rule out the possibility of transporting a large ensemble of particles, such as a human being or a spacecraft, via the phenomena. To be used for space travel, such a system would have to be of the “take me apart to get me there” kind, which is thought by many to be anywhere from impossible to very evil (As Douglas Adams has his characters sing in one of the Hitchhiker's Guide books “If you’ve got to take me apart to get there / I don’t wanna go” :D) Accelerating many massive particles to a high enough speed that the phenomena could “multiply” it to greater than c would entail the same terribly propulsion and energy requirements involved in making rockets capable of such speeds.

 

Another problem relates to signal gain – how much energy must be transmitted for a given amount of energy to be received. Though I neither have made nor am technically capable of a detailed calculation, the probability of a particle quantum tunneling some distance resembles a normal distribution, being large for very short distances and infinitesimally small as the distance becomes great. Refraction and reflection also affect the probabilities, in ways beyond my understanding. In short, the greater the distance tunneled with N & S’s or any other experiment, the lower the ratio of particles in to tunneling particles out. Using, as N & S did, powerful microwave emitters and sensitive detectors over table-top distances, this isn’t a severe issue. For “Tunnel-beaming” a signal interplanetary distances, it would be. I suspect that, as with many similar techniques, this one is a case of “work in principle, but requires the energy equivalent of whole galaxies of mass to transmit/transport modest signals/payloads”, similar to the Alcubierre drive (though distinct from it in having, apperantly, been demonstrated on a very small scale).

[freeztar]

Refraction and reflection also affect the probabilities, in ways beyond my understanding.

 

This statement is curious, Craig. What leads you to believe that refraction and reflection also affect the probabilities in the FTL scenario? :hihi:

[alexander]

so Jay, any comments on my code, am i correct in my "what if" thinking or is it totally off?

[Jay-qu]

Yeah I would say your correct insofar that the concept of velocity may need to be redefined. And it will probably be in some quantum-obscure way as to save relativity from needed change. Though as Craig pointed out, its not instant teleportation, just really really fast :)

[LaurieAG]

The experiment was originally published in 2004 and, while the diagram is the same as the one published in the New Scientist article, the wavelength of the microwave used is 33mm, roughly 1 1/3 inches.

 

You could use a constant 'moving' wave to identify the best entry angles (i.e. try many different angles) where strong signals are detected in both detectors and fine tune the start point of a 1 cycle 'moving' wave so that the majority of the wave goes across the gap to the second detector while the very last tip of the moving wave hits the back edge of the first prism almost tangentially. Because of the extreme angle of approach, this could be one of the few cases where the tip can rebound around inside the corner edges of the first prism before hitting the first detector.

 

The repeat rebounds, slowly moving towards their exit angle, would appear just like a 'tunneling' phenomena if it is viewed in respect to the points rebounding on the prisms back surface alone, in isolation from the rebounds ocurring in the rest of the prism. It must be a moving microwave so that both detectors can be triggered at the same instant from one complete moving cycle = 1 Microwave photon Equivalent, as reported in the New Scientist article.

 

Alternatively, if a continuous moving microwave is used the consolidated strength of microwave Photons hitting the first and second detectors over time should be in direct proportion to their respective frequency of occurrence at the angle being tested. I doubt if the frequency of detected microwaves are equal for both detectors.

 

A diagram of the original experiment, with correct wave paths would be nice.

[CraigD]

Refraction and reflection also affect the probabilities, in ways beyond my understanding.

This statement is curious, Craig. What leads you to believe that refraction and reflection also affect the probabilities in the FTL scenario?

A couple of reasons lead me to this conclusion.

 

First, fundamental, informal quantum mechanical optics. When particles interact, their wave functions are modified. Obviously, the probability of detecting a photon in a particular region at a particular time is altered dramatically if a mirror or a lens is placed between its emitter and that region, resulting in interactions between the photon and the reflecting/refracting media.

 

Second, this arrangement seems critical to the effect N & S are purportedly demonstrating. Without the reflective prisms in the arrangement, the early-arriving photons aren’t detected.

 

With my informal-at-best understanding of the physics of the experiment, a lot about it is mysterious to me. For example, why is it necessary to have the prisms at all? Why don’t emitted photons tunnel in media with no difference in refractive indexes, resulting in a regular, low-probability “fringe” of faster-than-light detections in practically every experiment involving precise photon travel time measuring experiments.

 

Like so much of quantum mechanics, the experiment has a weird character to it, reminiscent of the ”sawing a lady in half” stage magic trick. There’s an implication that the experiment somehow “remembers” when the two prisms were placed together to form an optically clear solid, though I’m pretty sure this is an misperception, and the experiment yields the same results whether the prisms were once together, or were always separated. Something about the phase of the light wave and the prisms’ higher-refractive index media – meaning, in particle physics terms, the greater number of virtual interactions between photons and the media’s atom’s electrons – seems critical to the photon “ignoring” the distance between the two prisms.

 

I’d love to have a better, more formal understanding of the physics involved.

The experiment was originally published in 2004 and, while the diagram is the same as the one published in the New Scientist article, the wavelength of the microwave used is 33mm, roughly 1 1/3 inches.

Got any links, Laurie, or even handmade sketches?

A diagram of the original experiment, with correct wave paths would be nice.

It surely would be!

 

I posted a simple, guesswork sketch here, but it’s simple, scaleless, and … guesswork.

 

PS: if there are no objections, I’ll move discussion of N & S’s experiment to its own thread, linked to from this and other threads that reference it. It’s a bit off the topic of this thread, which was more along the lines of the question of whether massive macroscopic stuff can travel faster than c