Hey guys I have an interesting topic for all of you who interested

[drphysica]

Hey guys I have an interesting topic for all of you who interested. From the EPR paradox we know that principle of non-locality indeed exist and yet it is suggests that information cannot be transferred between A and B due to quantum mechanics uncertainty principle since information gets scrambled by that uncertainty. But Nimtz and his co-workers at the University of Cologne transmitted Mozart’s 40th symphony as frequency modulated microwaves through an 11.4 cm length of barrier wave-guide at an FTL group velocity of 4.7 that of a ‘c’ receiving audibly recognized music from microwave photons that survived their barrier passage. So my question to all of you is, what causes the information to transfer faster then light without actually effecting the Einstein causality? I can see that the reality of the observer “us” is limited by the light cone and we don’t really know what happens out there on the other side and we might never will, however quantum mechanically it is possible that information is transferred FTL unless the quantum channelling experiment is some kind of a hoax. But if it is not, there is only one explanation to it. The information can be transferred superluminary without effecting the causality is if that information is “ethereal” and not “causal” thus no law special and general relativity holds and non-communication theory also holds. The non-locality of EPR experiment also suggests that all matter and energy in the universe as we know it is interconnected to every existence which is yet je ne sais quoi. What do you guys think?

 

[ZapperZ]

What you are describing is the apparent "superluminal tunneling". H. Winful has written a series of papers addressing this issue, and to me, it isn't convincing that such information did undergo a superluminal transfer.

You may find the following sources useful in addressing this issue:

H. Winful, PRL v.90, p.023901 (2003)
M. Buttiker and S. Washburn, Nature v.422, p.271 (2003)

The most recent comprehensive treatment of this issue was published by H. Winful, where he again expanded upon is PRL paper and explained away the apparent superluminal paradox in various tunneling phenomena.

H. Winful, Phys. Rep. v.436, p.1 (2006).

Zz.

 

[disregardthat]

Wouldn't the waves be going back in time then, if they traveled at 4.7 times c?

 

[sanman]

NonLocality = Universal TimeFrame (= Universal ReferenceFrame?)

Ah yes, tunnelling! That's the word I was thinking of in my sleep last night! Thanks for reminding me of it, as I wanted to bring it up with you all today.

Tunnelling is real. It's just as real as non-locality. Actually, it's the most immediate commonplace demonstration/manifestation of non-locality, isn't it?

So is Bell's Inequality the result of tunnelling then?

Regarding what you've said -- how do you differentiate between causal information and non-causal information?
Isn't any information going to be causal?

To me, if we accept non-locality, then this inherently means that Faster-than-C is *not* about going back in time.

Because non-locality means that the remote locale is perfectly synchronized with your own locale, so that by the time your effect reaches the remote locale -- whether propagated at C or whether FasterThanC -- the timeframe at the remote locale has already advanced anyway, in the same way that your own local timeframe has advanced. Doesn't that make sense? It's because all parts of the universe are identically synchronized in the same timeframe, if you believe in non-locality. It's only that effects which propagate at C take more time to reach the remote locales than the FasterThanC effects. It's not that time at the remote locale ceases to march on until it's felt the effects of your own locale.

Comments?

Hey, this is a good thread. Where can I find out more about this Nimtz experiment?

 

[disregardthat]

You would have to use complex numbers to find out the square root of the nominator in the relative factor equation right?
If we went in 10 times 'c'
1/quadr(1-v/c)
1/quadr(1-10)
1/quadr(-9)

what is the 'quadr' of -9? Is it possible to find out in complex numbers?

 

[sanman]

Paradox Shmaradox

Why should Faster-Than-C mean going back in time, or grandfather paradox?

If you and I are separated by a distance of 1 lightyear, then that means it will take me 2 years to reach you if I travel at half of C, 1 year to reach you if I travel at C, 6 months to reach you if I travel at 2C (not that I'm claiming one can travel Faster-than-C). My only point is that in all cases, the travel time is positive, and not negative. If C were defined as being infinity, then yes, I could then understand that traveling at C would mean instantaneous arrival (you arrive at your destination in the same moment you started out for it) and traveling faster than C would mean negative trip time (you arrive at your destination at a moment that is ahead of when you started out for it)

But lightspeed is NOT infinite, and therefore Faster-than-C travel would simply mean having a smaller fractional trip time than if you were traveling at C. After all, how does traveling a distance of 1 lightyear in 6 months mean you've gone back in time and arrived at a moment before you started? You've arrived 6 months after you started, and not ahead of when you started.

 

[DrChinese]

Here is a link to a related article by Herbert Winful:

http://arxiv.org/abs/quant-ph/0601085

 

[Hurkyl]

Why should Faster-Than-C mean going back in time?

It's an easy consequence of the Lorentz transforms. FTL travel, as measured in one frame, will be instantaneous in some frames, and it will be backwards in time in other frames.

If you and I are separated by a distance of 1 lightyear, then that means it will take me 2 years to reach you if I travel at half of C, 1 year to reach you if I travel at C, 6 months to reach you if I travel at 2C (not that I'm claiming one can travel Faster-than-C).

I assume that you all of these measurements are to be taken in my rest frame?

By your clock, incidentally, if you could travel at those speeds, SR predicts you would observe the trip as taking:

1.73 years,
0 seconds,
0.87 i years, (Yes, that's an imaginary number)

respectively.

 

[sanman]

I assume that you all of these measurements are to be taken in my rest frame?

By your clock, incidentally, if you could travel at those speeds, SR predicts you would observe the trip as taking:

1.73 years,
0 seconds,
0.87 i years, (Yes, that's an imaginary number)

respectively.

Hi Hurkyl,

Alright sure, I see that you're mentioning time dilation, so 2 years becomes 1.73 years by the traveler's clock. But if I'm traveling at C, why do you come up with 0 seconds?
As for .87i years, I'm not sure what the imaginary number translates to.

Even Stephen Hawking said he believes you could witness events from the past, but not alter them. We already know that if we witness a supernova tonight, we will be seeing an event that took place in the distant past. That doesn't mean we can travel back to the point in space and time when this event occurred. So traveling backwards in time is not possible.

As for traveling Faster-than-C, we know that virtual particles travel faster than C, and if they give a kick to a small particle, then it will travel (in tunnel fashion) faster than C as well.

 

[sanman]

So I want to once again ask -- doesn't non-locality inherently imply a universal reference frame?

Think about it -- if Alice and Bob later compare notes to see when the correlation violation at Bob occurred relative to the change in measurement at Alice, then their comparison will show that it occurred at the same moment within their respective localities. This result then automatically forces the conclusion that there is time synchronicity between the 2 remote localities.

So then doesn't this then mean there is a universal reference frame?

 

[Hurkyl]

But if I'm traveling at C, why do you come up with 0 seconds?

Because I computed it. Incidentally, I didn't invoke time dilation at all -- I did the whole calculation in my rest frame. If you traveled at c, the proper time you would experience would be zero. In my rest frame, your spatial displacement was one light-year. Your temporal displacement was one year. Thus, the proper time along your path was

$$\tau = \sqrt{ (1 \mathrm{\ yr})^2 - \frac{(1 \mathrm{\ lt\ yr})^2}{c^2}} = 0.$$

As for .87i years, I'm not sure what the imaginary number translates to.

Neither do I. IMO, that's a fair reason to reject FTL velocities.

As for traveling Faster-than-C, we know that virtual particles travel faster than C, and if they give a kick to a small particle, then it will travel (in tunnel fashion) faster than C as well.

Not having seen the math behind virtual particles, I feel hesitant to reply... but suggesting that an interaction between a virtual and a real particle can leave the real particle traveling FTL sounds like it goes against everything I've heard about quantum particles.

 

[Hurkyl]

Think about it -- if Alice and Bob later compare notes to see when the correlation violation at Bob occurred relative to the change in measurement at Alice, then their comparison will show that it occurred at the same moment within their respective localities. This result then automatically forces the conclusion that there is time synchronicity between the 2 remote localities.

Er, what are they comparing? The only thing Alice and Bob can ever see is the results of their measurements of the particles.

Incidentally, you cannot see a correlation violation in a single experiment -- you can only see it in the bulk statistics after performing many experiments.

 

[sanman]

Yes, you're right, I'm saying the experiment consists of multiple measurements, which is why I mentioned "change in measurement" (change occurring at some point(s) during this set of multiple measurements)

But they are able to each track when their events occurred, and experimental results show they occur instantaneously, don't they?

 

[Hurkyl]

Yes, you're right, I'm saying the experiment consists of multiple measurements, which is why I mentioned "change in measurement" (change occurring at some point(s) during this set of multiple measurements)

What change in measurement? At all points in time, Bob will find roughly half of the particles he measures will be spin up, and the other half will be spin down... no matter what Alice does.

 

[sanman]

Because I computed it. Incidentally, I didn't invoke time dilation at all -- I did the whole calculation in my rest frame. If you traveled at c, the proper time you would experience would be zero. In my rest frame, your spatial displacement was one light-year. Your temporal displacement was one year. Thus, the proper time along your path was

$$\tau = \sqrt{ (1 \mathrm{\ yr})^2 - \frac{(1 \mathrm{\ lt\ yr})^2}{c^2}} = 0.$$

Alright, fair enough -- you're saying that time is suspended within the traveler's reference frame, if he is traveling at C. Okay, I get you now.

Not having seen the math behind virtual particles, I feel hesitant to reply... but suggesting that an interaction between a virtual and a real particle can leave the real particle traveling FTL sounds like it goes against everything I've heard about quantum particles.

Well, quantum tunnelling is itself supposed to be due to the kicks from the virtual particles, otherwise what would cause the real particle to spontaneously tunnel? Like was being discussed in the other thread, if Planck's Constant were to shrink toward zero, then the kicks from the virtual particles would also shrink towards zero. And without the kicks, then there'd be no probability distribution, and hence no tunnelling. The kicks from the virtual particles are supposed to be happening FTL, which is why they are on the sub-Planck scale.

Which then makes me wonder about how shrinking to sub-Planck scale would be the way to achieve FTL. An electron is supposed to be a lepton point-charge, having no actual diameter. So doesn't that mean it's sub-Planck in size?
What about the neutrino? That's always moving at C, isn't it? So does it have any mass, or is that just an unconfirmed rumor?

 

[sanman]

What change in measurement? At all points in time, Bob will find roughly half of the particles he measures will be spin up, and the other half will be spin down... no matter what Alice does.

You don't have to measurements one-by one, you could do them together in batches, timestamping each one. You can record a correlation violation based on timestamp.

 

[Hurkyl]

Well, quantum tunnelling is itself supposed to be due to the kicks from the virtual particles, otherwise what would cause the real particle to spontaneously tunnel?

Particles don't have well-defined positions. (except during the instant we perform an idealized measurement of its position) You cannot say that it jumped from one side of the barrier to the other side of the barrier spontaneously. What happens is that, over time, the particle's wavefunction leaks past the barrier. At that point, if you measured its position, there is a nonzero probability that you'll find it on the other side of the barrier.

(This is all standard QM. I don't know what tunnelling looks like in the Bohm interpretation. I assume this is standard QFT too)

What about the neutrino? That's always moving at C, isn't it? So does it have any mass, or is that just an unconfirmed rumor?

The evidence suggests that Neutrinos oscillate, and thus they have mass. (And do not travel at c)

 

[Hurkyl]

You don't have to measurements one-by one, you could do them together in batches, timestamping each one. You can record a correlation violation based on timestamp.

Bob can't. When he does them in batches, he finds that roughly half of each batch is spin-up and half of each batch is spin-down, and that's all he can say.

Bob needs to actually see Alice's data before he can determine the correlation between his and her data.

 

[sanman]

I did indeed say that Bob and Alice compare notes later on -- meaning that he does later see Alice's data, and the difference between his and hers. I'm saying that he can record when he's taken each measurement, and LATER match up the time of the correlation violation to the time Alice changed her measurement method.

 

[Hurkyl]

I did indeed say that Bob and Alice compare notes later on -- meaning that he does later see Alice's data, and the difference between his and hers. I'm saying that he can record when he's taken each measurement, and LATER match up the time of the correlation violation to the time Alice changed her measurement method.

This wasn't clear to me. I still don't understand precisely what your experiment is, and what you hope to determine.


If Alice and Bob both measure their particles in sequential order, and if Alice changes her settings between the 100-th and 101-th particle, then they will find that the correlation for the first 100 particles will be different than the correlation for the next 100 particles. The actual times at which Alice and Bob measure their particles is entirely irrelevant.

If Bob measures his particles a whole year before Alice measuers hers... the correlations will be exactly the same as if Alice measured her particles a whole year before Bob measured his. (as measured in the usual Earth centered coordinate chart)

 

[sanman]

Entanglement vs Entanglement

Hmm, so let me just thrash this out in my head again.

The entanglement of the particles and the relative angular disposition of their respective collapsers (detectors) then together jointly constitute causality, while the correlation violation constitutes the effect (the necessary downstream consequence).

So our causal event is a composite event, with not one but a few things having to occur in order to set up the subsequent correlation violation.

Can we say that the requirement that the detectors be out of phase relative to each other amounts to a de facto "entanglement between the detectors"??


So a pair of mutually entangled objects will only yield correlation violations when interacting with another pair of mutually entangled objects??

Is that fair to say?

 

[Hurkyl]

I'm trying to determine the speed at which the correlation violation is capable of propagating from one locality to the other.

I really don't understand what it would even mean for a correlation violation to propagate.

meaning that the particles on each end will "know in advance" that their results will have to yield a correlation violation.

Er, yes, I suppose. We have a quantum system of two particles, and it's in a well-defined state.

A quantum state defines an expectation value for observables. Some observables can be interpreted as coincidences. Bell's theorem puts a restriction on the expected value of combinations of coincidences. Some of those combinations violate the restriction, when the quantum state is an entangled one.

Notice that none of the above has to do with experiment.

The point of a Bell test is to measure the expected value of certain coincidences, via repeated sampling. Once the expected value has been adequately estimated, one can check to see if the estimates violate the Bell theorem, and to what confidence level we can be sure the true values violate Bell's theorem.

You mean once 2 particles are entangled, they "know in advance" what is going to happen to both? Do 2 non-entangled particles therefore "know in advance" that Alice and Bob will eventually try to entangle them, and eventually try to keep their detectors out of phase by 45deg?

No, they don't. The system of two particles is simply in some quantum state. The experiment performed by Alice and Bob perform is simply a measurement of some aspect of that state.

 

[Hurkyl]

Oh bleh, you deleted the other post. I still think my reply will be useful.


There is, incidentally, a nice, visual picture for a single qubit. The quantum state of a qubit is simply a point on the unit sphere, known as the Bloch sphere.

If we define "spin-up" to be +1, and "spin-down" to be -1, then any quantum state corresponds to the point:

(E[x], E[y], E[z])

on the unit sphere. E[x], here, is the expected value of a measurement about the x-axis. Or, to express it differently, if we measured the spin about the z-axis of the quantum state denoted by the point

(a, b, c)

on the unit sphere, then we have:

P(spin-up) - P(spin-down) = c.



For a system of two qubits, the quantum state is some six-dimensional space. Classically, we'd expect 4-dimensional: two dimensions per qubit. This is the main way in which quantum mechanics differs from classical mechanics.

 

[sanman]

No, they don't. The system of two particles is simply in some quantum state. The experiment performed by Alice and Bob perform is simply a measurement of some aspect of that state.

Hurkyl, let me just reduce the Bell's Inequality experiment to the scenario of an entangled pair being collapsed by another entangled pair. The point is that the results/outcomes of the interactions between members of 2 different entanglements depend upon the interactions between their respective mates.

Somehow some degree(s) of freedom seem lost between the 2 remaining prospective interactors, once their respective mates have already interacted.

 

[drphysica]

Hey I think I have a theory. Form QM mechanics we know that wave-function supports the idea that particle exists everywhere in event space and the Nimz experiment suggests that the tunnelling of photons occurs FTL but what we didn’t realized that if the wave-function exists everywhere until measured or collapsed there is also a possibility that it existed outside the event space or light cone. Which means the observation we done on the wave function is only restricted it locally thus within the light cone. But the event space outside the light cone connects our future and a past and is not observable at all so what I’m trying to say is that it is like the idea with EPR. Let's say hypothetically, we have a particle which decays into two other particles and one travels in direction of the future and one into the past (I know it’s crazy) but again the analogy suggests that one went into the future is still connected to the one went into the past just like the light cone it has light direction going into the past and the future, so it is possible that quantum channelling suggest that the information is arrived from possible future by being interconnected to the present and the past without violating causality.

 

[ZapperZ]

I strongly suggest you read the Winful papers before making such a conclusion.

Furthermore, there's nothing special about photon tunneling. I've done the same with electron tunneling and the description is identical when you deal with free electrons. In none of these are there any indication of "FTL" transfer. The tunneling matrix element do not imply such a thing.

Zz.

 

[drphysica]

Thank buddy I will, just didn't have the time. :)

 

[drphysica]

Yep that resolves that question regarding the experiment. But I still will agree with statement that “a physical theory is said to exhibit nonlocality if, in that theory, it is not possible to treat widely separated systems as independent” (as in EPR paradox). You got to love quantum mechanics. :-)

 

[ZapperZ]

Yep that resolves that question regarding the experiment. But I still will agree with statement that “a physical theory is said to exhibit nonlocality if, in that theory, it is not possible to treat widely separated systems as independent” (as in EPR paradox). You got to love quantum mechanics. :-)

There is a HUGE difference between "non-locality" in QM and "FTL" transfer of information. Zeilinger, in all of his papers regarding the experimental verifications of EPR-type measurement, never once advocated any FTL transfer of information. In fact, there have been a few papers (Dr. Chinese can verify this) that clearly show that no FTL signal can be sent even using such "non-local" entanglement.

Thus, I do not understand the implication of FTL transfer within the context of the non-locality of quantum entanglement. I mean, this is such an obvious issue that one must know that it has been tackled already, and it has!

Zz.

 

[drphysica]

Indeed that concludes that FTL is not possible! And yep there is no transfer of information in non-locality of QM just as I mentioned in the original question coz no-communication theory prohibits it anyway. Thankz!

 

[sanman]

Alright, but then you're saying that there are no implications or consequences arising from Non-Locality. Because if that remote locale can never affect you directly due to "No Communication Theorem" then the non-locality might as well not exist.

But what further experiments could one devise to usefully probe the nature of the mechanism underlying entanglement?

If Alice and Bob each were to take a Kerr Rotation measurement of each of their particles immediately prior to subjecting each particle to the Bell's Inequality measurement experiment, then would the correlation violation still appear once they had a chance to later compare data?

Because the definition of Kerr Rotation is that it would not alter the state of a particle being measured (even if it is destroying the entanglement).

 

[drphysica]

Alright, but then you're saying that there are no implications or consequences arising from Non-Locality. Because if that remote locale can never affect you directly due to "No Communication Theorem" then the non-locality might as well not exist.

No that is not what I'm saying, what I'm saying is that the quantum mechanics is a theory which exhibit that it is not possible to treat widely separated systems as independent, and that occurs due to non-locality. So you see the no-communication theory and relativity holds. Otherwise fundamental laws of physics will be violated. That is why I love QM! :-)

 

[disregardthat]

Does anyone have an easy explanation or a link to an easy explanation of imaginary numbers? I don't get what you are discussing here.

 

[sanman]

But then what are the implications and consequences arising from Non-Locality?
We can see Non-Locality after the fact, after Bob and Alice have later gotten a chance to compare data by classical means).

What does it mean to have Non-Locality that is only accessible via classical channels? Depending upon classical channels of communication then once again forces Locality.

If there is interdependence of widely separated systems, then that interdependence must be occurring through some mechanism. It is this mechanism which must be found, if QM and GR are to be reconciled.

 

[drphysica]

If there is interdependence of widely separated systems, then that interdependence must be occurring through some mechanism. It is this mechanism which must be found, if QM and GR are to be reconciled.

That is what I thought when I psoted this thread on assumption that quanum channeling experiment suggested that info. could travel FTL but now it is clear tha there is no underlying mechanism it is what it is a quantum mechanics showing us deeper sides of reality. I used the analogy of the waves on a beach to describe it in one of my forums.