It?s another bad day for Einstein!

[Rudy Toody]

Science News article.

 

[Born2bwire]

Unless I missed it, the article does not explain how this violates special relativity. It just seems to be a better measurement of quantum entanglement.

 

[herm0016]

"He either has to give up relativity or embrace quantum mechanics."

he must do neither. we still use Newtonian mechanics and they only proximate things. hell, in the realm of thermal science we are good if we get within 20 percent of what we find experimentally in a fully developed flow in a known length and diameter pipe. his equations and theory still predict experimental results.

 

[Foxery]

information would have to travel the 18 kilometers separating the two towns in virtually no time. The team couldn?t prove that information traveled instantaneously. But because their experimental errors were limited to time differences of less than one-third of a billionth of a second, they could prove

Sorry, they lost my attention here. The article is poorly written, and really doesn't show any convincing data or coherent explanation of how this experiment can possibly "prove" anything.

The concept of quantum entanglement has been around - but has anyone shown that it can be used to transmit and receive useful, coherent information, or only data points on an experimentor's graph?

 

[CycloWizard]

Maybe this is juvenile and stupid, but I had a thought. Is it possible that there is another dimension through which the information travels at a speed capped by the speed of light? I'm not familiar enough with recent physics theories to know if anyone has considered that, and it's been an awfully long time since I took physical chemistry.

 

[herm0016]

hmm.. i should have actually read the article. it is horribly written, and that is nothing new, we have seem quantum entanglement in lots of experiments. it could be the fact that they started out the same that makes them end the same, instead of one sending information at the end of the route, they both start with the same info, so they both end with the same result. my theory does not violate relativity, and its possible in quantum mechanics.

 

[herm0016]

Originally posted by: CycloWizard
Maybe this is juvenile and stupid, but I had a thought. Is it possible that there is another dimension through which the information travels at a speed capped by the speed of light? I'm not familiar enough with recent physics theories to know if anyone has considered that, and it's been an awfully long time since I took physical chemistry.

in short.. that is what string theory predicts.

 

[Rudy Toody]

You have to admire Richard Feynman for sitting night after night in a go-go bar until watching the little shimmy outfits gave him the Golden Moment necessary to create string theory.

I have to admit that I did the same thing in those days, but not once did I think of physics!

 

[PowerEngineer]

Originally posted by: herm0016
hmm.. i should have actually read the article. it is horribly written, and that is nothing new, we have seem quantum entanglement in lots of experiments. it could be the fact that they started out the same that makes them end the same, instead of one sending information at the end of the route, they both start with the same info, so they both end with the same result. my theory does not violate relativity, and its possible in quantum mechanics.

I agree that this seems to be another experiment confirming quantum entanglement.

Based on my uncertain understanding of quantum physics, I think it's more accurate to say that the photons started out entangled rather than "started out the same". It seems that the probability wave representing the likelihood of possible states isn't forced to collapse to an actual state until you attempt to measure its state. Once the first of the pair has been measured, then the entanglement ensures that its partner will have the same state when it is measured. I seem to recall that there was a very clever experiment that demonstrated this; I think this is it. In any event, I can't see how this can be used to transmit information unless you could dictate the state of the first photon rather than just measure it.

 

[silverpig]

I read the actual paper. I need some background on a Franson interferometer before I can make any comments

 

[Born2bwire]

Originally posted by: silverpig
I read the actual paper. I need some background on a Franson interferometer before I can make any comments

It works on the same principle as your standard Rockwell Automation retro encabulator.

 

[f95toli]

It is just another quantum entanglement experiment, they have been around for decades.

The main point of this work is that the photons are travelling so far that there is no way you could get this results WIHTOUT entanglement unless the photons were "communicating" using a mechanism that allowed FTL communication.

Now, to someone that accepts the results of QM this is not surprising (I don't think anyone seriously belives that entanglement can be explained using FTL communication).

The "bad day for Einstein" title is due to the fact that Einstein never did accept QM, he thought that experiments like this were impossible. He co-authoured a famous paper about this, the so-called EPR "paradox", the point of which was to show that QM made unreasonable predictions. He was wrong (or to be nore precise, they are "unreasonable" but still turn out to be correct).

Hence, while this is a neat experiment but the outcome is not at all surprising.

 

[ch33kym0use]

Einstein said that imagination is more important than knowledge.

 

[Foxery]

ArsTechnica did a much cleaner writeup today, found here.

Of note:

Although this sounds like it can be used for information transfer, it cannot, so special relativity is safe.

They also do a much better job of explaining what this experiment demonstrated.

 

[f95toli]

I looked at the paper when I came to work this morning and it is essentially just an ordinary test of a Bell-type inequality (i.e. the fibers are just arms in a big interferometer). As far as I can tell there is no new physícs in the paper and much of the text deals with how they overcame problems with the fibers etc.
Hence, as I suggested above it is a neat experiment but the result is not surprising

 

[CycloWizard]

Originally posted by: f95toli
I looked at the paper when I came to work this morning and it is essentially just an ordinary test of a Bell-type inequality (i.e. the fibers are just arms in a big interferometer). As far as I can tell there is no new physícs in the paper and much of the text deals with how they overcame problems with the fibers etc.
Hence, as I suggested above it is a neat experiment but the result is not surprising

Can you give a brief description of quantum entanglement? From the context, I take it to mean that there is some correlation of properties or behavior for particles being pulled from the same distribution/source, but I've never really read anythin on it.

 

[Born2bwire]

Originally posted by: CycloWizard

Originally posted by: f95toli
I looked at the paper when I came to work this morning and it is essentially just an ordinary test of a Bell-type inequality (i.e. the fibers are just arms in a big interferometer). As far as I can tell there is no new physícs in the paper and much of the text deals with how they overcame problems with the fibers etc.
Hence, as I suggested above it is a neat experiment but the result is not surprising

Can you give a brief description of quantum entanglement? From the context, I take it to mean that there is some correlation of properties or behavior for particles being pulled from the same distribution/source, but I've never really read anythin on it.

When the two particles are emitted, in this case photons I believe, they are part of a single system causing the wavefunction to define the system to be dependent upon both photons. However, the photons cannot have the same characteristics, so if one is say "spin up" then the other must be "spin down" (I don't recall what characteristic(s) they are comparing but spin is a common one). So if we were to measure one of the photons, causing the wavefunction to collapse, then we instantly know the characteristic of the other photon. This propagation of states occurs instantaneously and would appear to violate special relativity in terms of the speed of light. This is refuted by physicists stating that there is no means of actually propagating information this way. You cannot cause one of the photons to have a desired state when you do your measurement. Bell's theorem, which is an expansion on the EPR paradox, gives a way of telling if the photons determined their individual properties when they were created/emitted (and carry this information via some hidden variable as would be according to the school of QM that Einstein believed in) or if they truly followed the wavefunction, only choosing a state upon measurement (as per the Copenhagen QM school of thought). One thing that I always admired about the EPR paradox, is that despite Einstein and the other authors being wrong on their interpretation of quantum mechanics, they still followed good science to come up of a way that could test their theory and which ultimately allowed Bell to help cement the Copenhagen school of thought.

 

[racolvin]

Good heavens .... I don't understand 1/4th of all this .. I just come to Highly Technical to bask in intellectual glow

 

[Born2bwire]

Originally posted by: racolvin
Good heavens .... I don't understand 1/4th of all this .. I just come to Highly Technical to bask in intellectual glow

Don't tell anyone, but we just make this stuff up.

 

[xts3]

Originally posted by: CycloWizard
Maybe this is juvenile and stupid, but I had a thought. Is it possible that there is another dimension through which the information travels at a speed capped by the speed of light? I'm not familiar enough with recent physics theories to know if anyone has considered that, and it's been an awfully long time since I took physical chemistry.

This is a really good thought I was thinking about this today but in a different way, what if space is just 'twisted' and 'stretched', and all movements from allowed movement spaces are instantaneous. Say if we take a rubber band and we make 'movement spaces' (i.e. allowed spaces in which something can move/jump to instantaneously sequentially, i.e. you can't skip a movement node) and we stretch the rubber band, we don't violate the speed of light, we merely stretch out the spaces in which the object can lawfully move, and it only seems to travel faster then the speed of light. Kind of like us walking on a conveyer belt which is being stretched.

 

[hellokeith]

Hrmm, I wonder if the detection mechanism on one end could be drastically altered on a known frequency/pattern, such that the entangled photon on the opposite end displays the inverse of that pattern?

Also, is it possible to split an already-split photon into 2 more photons, and if so, how would those 2 photons relate to the other original entangled photon from the first split group.

x --> split --> a [entangled] b
b --> split --> c [entangled] d
How do c & d relate to a ?

Edit:

Well it appears negative to both my questions:


http://en.wikipedia.org/wiki/EPR_paradox

according to quantum mechanics, it is fundamentally impossible for her to influence what result she gets


http://en.wikipedia.org/wiki/No_cloning_theorem

The no cloning theorem is a result of quantum mechanics which forbids the creation of identical copies of an arbitrary unknown quantum state.

 

[PolymerTim]

I did a little reading on the topic and found a helpful link I think you guys might like. It starts off cery simple for those with little physics background:
http://davidjarvis.ca/entanglement/

but quickly gets to meatier material including how to produce quantum entangled photons:
http://davidjarvis.ca/entanglement/spookiness.shtml

If I understand correctly from this and other reading, in an entangled pair you can change the state of one of th pair by changing the other and the effect is instantaneous. The problem is that as soon as you measure the state of either of the pair, they become unentangled. So, in theory, I guess you could flip polarization states of entangled photons like morse code, but you can't transmit information this way because as soon as you try to read one, they become unentangled. Freaky stuff if you look at the examples on the latter link that show the effect of interference patterns of entangled and individual photons.

Somewhere (probably wikipedia), I saw an explanation for the reason of the instantaneous transfer is that in quantum states, the information about the change in one of the pair travels symmetrically in time both forward and backwards into the past. So they idea is that information travels back in time at or below the speed of light to the point where the entangled pair originated, then transfers information to the other half of the pair which then carries it forward to the future time. The two time travels cancel out and the effect is instantaneous.

Weird stuff: or I guess I should say spooky in honor of Einstein. Now why this happens just totally blows my mind. It will be interesting to see what comes of this in the future.

 

[PolymerTim]

Originally posted by: hellokeith
Hrmm, I wonder if the detection mechanism on one end could be drastically altered on a known frequency/pattern, such that the entangled photon on the opposite end displays the inverse of that pattern?

Also, is it possible to split an already-split photon into 2 more photons, and if so, how would those 2 photons relate to the other original entangled photon from the first split group.

x --> split --> a [entangled] b
b --> split --> c [entangled] d
How do c & d relate to a ?

Edit:

Well it appears negative to both my questions:


http://en.wikipedia.org/wiki/EPR_paradox

according to quantum mechanics, it is fundamentally impossible for her to influence what result she gets


http://en.wikipedia.org/wiki/No_cloning_theorem

The no cloning theorem is a result of quantum mechanics which forbids the creation of identical copies of an arbitrary unknown quantum state.

I think it should be possible to split them, they just won't be identical (to not violate the cloning rule). For instance, when two photons are split, they have opposite polarization states. Now what happens through multiple splits I have no clue about.

 

[Rudy Toody]

I have always viewed this as being a pipe full of marbles with the photons starting out in opposite directions from the midpoint of the pipe. At the time of measurement, half a marble will be protruding from each end of the pipe. The act of measuring causes the marble at that end of the pipe to be pushed in by the length of its radius. The marble at the other end pops out. This would be a small motion that appears to send information faster than the speed of light.

Edit: I have considered testing this idea, but I have lost all my marbles!

 

[Rudy Toody]

An alternate view using only spin: Imagine an infinite line of identical gears. We start at the midpoint where the Left Gear is rotating clockwise and the Right Gear is rotating counterclockwise. When we measure the rotation at one end some distance from the midpoint, we would know that since the time (number of gears from the midpoint) for the two opposite gears will be an even value, we know that whatever we get from the measurement the opposite end will be the opposite rotation.

I have considered testing this idea because I still have all my gears!