Photon's puzzle.

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Re: Photon's puzzle.

Postby Braininvat on September 16th, 2017, 1:08 pm 

For me, the "superluminal" information concept is rather misleading, AFAICT. (which isn't that far) It's like having a very long tether in space holding two astronauts at each end. The tether is designed so that their heads point in opposite directions. If Astronaut Bob has his head pointing towards Galactic North, then Astronaut Alice will point towards Galactic South. That's just how the tether is twisted or whatever. Any two objects attached this tether-with-a-twist will be "entangled" in this way. If I cut the tether in the middle, it is certainly true the quantum state of Alice and Bob changes instantly, but there is no FTL communication of that change of state. They are instantly no longer entangled, but any actual information that could travel along the tether (like feeling the jerk of disconnection, say) would propagate at C, or slower. Bob doesn't know he's lost his connection to Alice until that information reaches him at a finite rate of travel. And before, he didn't know that his head was pointed north because Alice's was pointed south (they are a fermionic couple?), unless he received a message at lightspeed from Alice confirming their strange entanglement.

There's nothing like trying to grasp quantum physics with mild sexual innuendoes.
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Re: Photon's puzzle.

Postby mitchellmckain on September 16th, 2017, 1:53 pm 

Braininvat » September 16th, 2017, 12:08 pm wrote:For me, the "superluminal" information concept is rather misleading, AFAICT. (which isn't that far) It's like having a very long tether in space holding two astronauts at each end. The tether is designed so that their heads point in opposite directions. If Astronaut Bob has his head pointing towards Galactic North, then Astronaut Alice will point towards Galactic South. That's just how the tether is twisted or whatever. Any two objects attached this tether-with-a-twist will be "entangled" in this way.

There are severe problems with this analogy. It is more like a tether between the direction they are thinking at a particular moment and if you ask them what direction they are thinking then the tether is immediately broken when you ask. You only get that one correlation between their answers when the question is asked and then the connection disappears. Furthermore, there is no reason to believe they even have thoughts about a direction before the question is asked, so imagining a causal connection between their thoughts before the question is asked is not warranted. Finally their answers are 100% completely random and it is established that there are no pre-existing conditions which determine the answers they give.

...but that is the way of analogies... There are always aspects which are the same and others which are not.

Braininvat » September 16th, 2017, 12:08 pm wrote:If I cut the tether in the middle, it is certainly true the quantum state of Alice and Bob changes instantly, but there is no FTL communication of that change of state. They are instantly no longer entangled, but any actual information that could travel along the tether (like feeling the jerk of disconnection, say) would propagate at C, or slower. Bob doesn't know he's lost his connection to Alice until that information reaches him at a finite rate of travel. And before, he didn't know that his head was pointed north because Alice's was pointed south (they are a fermionic couple?), unless he received a message at lightspeed from Alice confirming their strange entanglement.

There's nothing like trying to grasp quantum physics with mild sexual innuendoes.

This part is ok, for example -- ways in which the analogy is the same.

But then there are the issues with simultaneity and assumptions about the absence of interference.
1. You are obviously going to make the two measurements at a space like interval (so no communication could occur between them. Then it should be noted that neither is actually first in any objective way. So talking about one measurement affecting the other cannot be anything but a subjective imposition.
2. It is not like this entanglement is immune to outside effects breaking the connection and at large distances that is going to be difficult to ensure.
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Re: Photon's puzzle.

Postby bangstrom on September 17th, 2017, 2:44 am 

BurtJordaan » September 16th, 2017, 11:33 am wrote:
bangstrom » 16 Sep 2017, 05:50 wrote:A non-local, faster than light exchange of quantum information is necessary if the paired particles are to simultaneously decide their identities. This is not the same thing as intelligible information that we can use but it is an exchange of information just the same. Quantum information.

Bang, I think you have your own private definition of what quantum information and the transfer of such information means. I have not seen any scientific publication that would agree with your definitions. The collapse of wavefunctions, or whatever name you want to give to it, don't transfer information (even of the quantum type) super-luminally.

Maybe there exists some form of "pseudo information" that agrees with you, so I hope a quantum physicist joins this conversation, because I simply don't know enough about the subject to give you the clinching evidence against your position.


There are alternatives to the term “quantum information” and it has its detractors but the use of the term is not unusual in the scientific literature and I favor it over the more esoteric bits of jargon.

Here is an article from Wiki. where it is alternatively called “information,” “communication,” or “quantum information.”
https://en.wikipedia.org/wiki/Quantum_entanglement

And here is a segment from the article relative to what I have been saying about entanglement.

"It thus appears that one particle of an entangled pair "knows" what measurement has been performed on the other, and with what outcome, even though there is no known means for such information to be communicated between the particles, which at the time of measurement may be separated by arbitrarily large distances.

“This has been shown to occur even when the measurements are performed more quickly than light could travel between the sites of measurement: there is no lightspeed or slower influence that can pass between the entangled particles.[6] Recent experiments have measured entangled particles within less than one hundredth of a percent of the travel time of light between them.[7] According to the formalism of quantum theory, the effect of measurement happens instantly.[8][9] It is not possible, however, to use this effect to transmit classical information at faster-than-light speeds[10] (see Faster-than-light § Quantum mechanics).
Quantum entanglement is an area of extremely active research by the physics community, and its effects have been demonstrated experimentally with photons,[11][12][13][14] neutrinos,[15] electrons,[16][17] molecules the size of buckyballs,[18][19] and even small diamonds.[20][21] “
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Re: Photon's puzzle.

Postby bangstrom on September 17th, 2017, 3:02 am 

Braininvat » September 16th, 2017, 12:08 pm wrote: Bob doesn't know he's lost his connection to Alice until that information reaches him at a finite rate of travel. And before, he didn't know that his head was pointed north because Alice's was pointed south (they are a fermionic couple?), unless he received a message at lightspeed from Alice confirming their strange entanglement.

The problem with the analysis is that, when the connection is lost instantly for both Alice and Bob, their orientation is becomes fixed instantly and their common connection is lost instantly. There is no jerk to be felt or signal propagation time through the tether or even a tether. That is the end of their entanglement. When Alice’s position is fixed, Bob position is also fixed and the timing of both events is either simultaneous or far too fast to measure.

This is the Wiki article I sited earlier in case you missed it.
https://en.wikipedia.org/wiki/Quantum_entanglement

"Quantum entanglement is a physical phenomenon that occurs when pairs or groups of particles are generated or interact in ways such that the quantum state of each particle cannot be described independently of the others, even when the particles are separated by a large distance—instead, a quantum state must be described for the system as a whole."
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Re: Photon's puzzle.

Postby BurtJordaan on September 17th, 2017, 3:45 am 

Bang, I think we are all saying the same as the Wiki-article. My debate with you is that it does not show instantaneous quantum information transfer, unless you have your own definition for "quantum information". Decoherence of entangled particles does not transfer information, because the receiver has no idea why the decoherence happened or in which state the pair was before the collapse, because any 'peeking' collapses it.

This Wiki gives a reasonably standard picture of the term: https://en.wikipedia.org/wiki/Quantum_information.
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Re: Photon's puzzle.

Postby bangstrom on September 17th, 2017, 5:04 am 

BurtJordaan » September 17th, 2017, 2:45 am wrote:Bang, I think we are all saying the same as the Wiki-article. My debate with you is that it does not show instantaneous quantum information transfer, unless you have your own definition for "quantum information". Decoherence of entangled particles does not transfer information, because the receiver has no idea why the decoherence happened or in which state the pair was before the collapse, because any 'peeking' collapses it.

This Wiki gives a reasonably standard picture of the term: https://en.wikipedia.org/wiki/Quantum_information.

I hope you aren’t making this a mater of semantics.

If I see a flash of light, I may have no idea why it happened, or where it came from or how, or the state of the object that emitted the light, or if I just imagined it but I got a signal of “information” from somewhere even if it was only in my head or from something I ate. I was informed but not necessarily in the classical sense.

A single Q-bit of quantum information is not sufficient to qualify as a classical bit of information but it is information just the same. Quantum information.

From Wiki,”A unit of quantum information is the qubit. Unlike classical digital states (which are discrete), a qubit is continuous-valued, describable by a direction on the Bloch sphere. Despite being continuously valued in this way, a qubit is the smallest possible unit of quantum information. The reason for this indivisibility is due to the Heisenberg uncertainty principle: despite the qubit state being continuously-valued, it is impossible to measure the value precisely.”

If two particles are a great distance apart and the observation of one simultaneously affects the other, there must be something resembling a communication going on no matter what you choose to call it.

Quantum information is not a word I made up or something not found in the literature. It even has its own journal. http://www.worldscientific.com/worldscinet/ijqi

The International Journal of Quantum Information (IJQI) focuses on the interdisciplinary field of Quantum Information Science. We welcome theoretical and experimental contributions in the areas of Quantum Computation, Quantum Communication, Quantum Cryptography and Fundamentals of Quantum Mechanics.
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Re: Photon's puzzle.

Postby BurtJordaan on September 17th, 2017, 5:50 am 

bangstrom » 17 Sep 2017, 11:04 wrote:I hope you aren’t making this a mater of semantics.

Not at all. It is about your claim that quantum information (qubits or whatever) can be spatially displaced faster than what a photon can be. My argument is that superluminal effect that you are talking about, is not quantum information transfer.

If two particles are a great distance apart and the observation of one simultaneously affects the other, there must be something resembling a communication going on no matter what you choose to call it.


OK, but then do not call it 'quantum information', because that has a scientific meaning, which I do not think includes what you are ascribing to it. I do not know a straightforward term for it, but maybe someone around here can help us out.
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Re: Photon's puzzle.

Postby ralfcis on September 17th, 2017, 9:01 am 

He's saying a change is made from not-knowing what state something was to knowing what state it's in. It's like when, in the movie Dumb and Dumber, Jim Carrey asks Lauren Holly what his chances are and she answers one in a million and he responds, "So you're saying there's a chance." He thinks a change has been made in his chances but really there's no useful information in just knowing a change has been made. She provided him with no useful information and everyone watching the comedy can laugh at the dumbness of his interpretation.
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Re: Photon's puzzle.

Postby bangstrom on September 17th, 2017, 2:36 pm 

BurtJordaan » September 17th, 2017, 4:50 am wrote:
bangstrom » 17 Sep 2017, 11:04 wrote:I hope you aren’t making this a mater of semantics.

Not at all. It is about your claim that quantum information (qubits or whatever) can be spatially displaced faster than what a photon can be. My argument is that superluminal effect that you are talking about, is not quantum information transfer.

If not a “quantum information transfer” then what is it? I can’t explain anything if you say my terminology is wrong or not the way science defines it. We don’t have a common language.

We can both look up ‘quantum information transfer’ to understand how it is defined in QM and my understanding is that the definition of ‘quantum information transfer’ includes the simultaneous swapping of quantum identities and simultaneous is not a speed.

It is certainly faster than the relativistic time delay of one second for every 300,000 km of distance that we observe for light related events.

BurtJordaan » September 17th, 2017, 4:50 am wrote:
If two particles are a great distance apart and the observation of one simultaneously affects the other, there must be something resembling a communication going on no matter what you choose to call it.

OK, but then do not call it 'quantum information', because that has a scientific meaning, which I do not think includes what you are ascribing to it. I do not know a straightforward term for it, but maybe someone around here can help us out.

The straight forward term is the same as always, “die spukhafte Fernwirkung.”
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Re: Photon's puzzle.

Postby BurtJordaan on September 24th, 2017, 4:48 am 

bangstrom » 17 Sep 2017, 20:36 wrote:The straight forward term is the same as always, “die spukhafte Fernwirkung.”

The most accessible modern technical paper (connected to the subject) that I could find is "The Limits of Entanglement" (2012) by Chad Orzel. Although Orzel does not use the term, one can perhaps understand his examples as "decorrelation between quantum states". As he describes it, it is less of a "spooky action at a distance"...

I don't think this is quite the same thing as "decoherence", because I understand that as a gradual loss of phase coherence over time.
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Re: Photon's puzzle.

Postby ralfcis on September 24th, 2017, 8:29 am 

Before Einstein came up with his clock sync method, the present was viewed as an instantaneous common moment for all points in space. But after Einstein, the present was redefined to be subject to the speed of light delay. All clocks on a timeline were synced to say the same time based on the speed of light delay between them. You can see this on a Minkowski STD where each point on a line of present transmits a light signal back to the ct-axis it's common clock reading but the delay in sending back that reading means none of the points are sharing a true simultaneous instantaneous present.

Relativistic simultaneity is not the instantaneous present of entanglement or the instantaneous present that light travels in an Epstein STD. The Epstein depiction of light shows it as a horizontal line where light is simultaneously, from its perspective, at every point in space. There are no units for light speed in the Epstein STD but in the Minkowski it looks as though the units for c are 1ly/yr (although people won't admit that).

Einstein's clock sync method already introduces the circular argument that it uses the speed of light to sync clocks used to measure the speed of light. But in redefining the present to being limited by the speed of light, does it artificially introduce further circular arguments that unduly influence relativity itself? The Epstein STD doesn't have these problems and it is identical to the Minkowski STD except that the ct and ct' axes are swapped. Somewhere here is the resolution between relativistic simultaneity (light speed limited) and instantaneous simultaneity (entanglement and photon perspective).
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Re: Photon's puzzle.

Postby ralfcis on September 26th, 2017, 4:25 pm 

So I'm saying Einstein's clock sync method changed the very definition of the word present to suit his own ends and no one has a comment, confirmation or denial? Is there a proof that the present is an artificially created clock sync network to accommodate the speed of light delay? Is this the fundamental assumption that allows relativity to explain relativistic phenomena?
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Re: Photon's puzzle.

Postby BurtJordaan on September 26th, 2017, 5:06 pm 

Ralf AFAIK, Einstein never used words like "the present". He defined a sensible convention for simultaneity in inertial frames, based on his intuition that one cannot detect inertial movement from within an inertial system. In other words the principle that all inertial frames are equivalent and all inertial motion is relative.

It is hard to argue against that - probably futile...
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Re: Photon's puzzle.

Postby ralfcis on September 26th, 2017, 9:02 pm 

Ok in the context of this discussion: simultaneity in quantum physics, as in entanglement, is instantaneous. Simultaneity in relativity is limited by the speed of light (except if things could travel at the speed of light then from their perspective they would be simultaneously and instantaneously at all points in space).

In relativity, all clocks are sync'd throughout space to the same time on the clock taking into account the speed of light delay between clocks. Relativity's definition of simultaneity in an inertial frame is what happens at different points in space at the same sync'd clock reading.

When one guy reports what happened to him at t=1 and a guy 1 ly away reports what happened to him at t=1, his clock has been corrected so that his t=1 has happened 1 year before the first guy's clock hits t=1. The speed of light delay has been subtracted from the 2nd guy's clock. The events are 1yr off and add to that 1 1 yr delay for the info to travel, the report that reaches the 1st guy is what happened to the 2nd guy 2 years ago. Simultaneous events in a universal instantaneous present happened 1 year apart in a relativity's definition of simultaneity or am I mixing something up.
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Re: Photon's puzzle.

Postby BurtJordaan on September 27th, 2017, 2:35 am 

ralfcis » 27 Sep 2017, 03:02 wrote: Simultaneous events in a universal instantaneous present happened 1 year apart in a relativity's definition of simultaneity or am I mixing something up.

You are definitely mixing things up. ;)

Simultaneity in SR is private to each inertial frame and is how clocks are synchronized in each inertial frame separately, using light as you said, according to the Minkowski metric. It only works in a perfectly empty universe that does not expand or contract.

The "universal instantaneous present" is something we use in cosmology, but there it is not described by inertial frames - we use the Friedmann–Lemaître–Robertson–Walker (FLRW) metric, that covers the observable universe. We assign spacetime coordinates according to this metric, which implies a universal cosmic time.

But that's a long story, not suitable for this thread.
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Re: Photon's puzzle.

Postby ralfcis on September 27th, 2017, 8:16 am 

Yes. as I stated in the previous post, I'm only talking about within an inertial frame. Setting all the clocks to the same time within that frame does not make them simultaneous unless you buy into how relativity defines simultaneity which involves Einstein's clock sync method.

The only way they could be truly simultaneous is if the same time reading on both clocks did not indicate instantaneous simultaneity. So I'm saying if the clocks were not sync'd using Einstein's method, a universal instantaneous present would exist within that frame. If a far guy transmitted his time and the 1st guy knew he was 1 ly away, the 1st guy would subtract a year from both their times to determine what events happened simultaneously, instantaneously a year ago.But if he followed the Einstein method and just trusted the far clock's reading was set to the same simultaneous present time as his own, the events would be off by a year. If this type of simultaneity is defined within an inertial frame, how weird does the concept become when the frames start relatively moving? The fact that it isn't weird between moving frames must mean I am not understanding the concept of relativistic simultaneity within an inertial frame. So where am I mixing it up is my question.

Without Einstein's method, between moving frames, the clock times would be noted when they crossed paths. Times would not need to be compared to a pre-determined clock network, as in the Einstein scheme, but could be compared between transmissions of clock times from the frames. There would be no sync'd clock network.

I think it would be very interesting to see what kind of STD of the inertial frame would come about based on the FLRW clock scheme. I now don't trust the the current STD depiction of inertial spacetime as the horizontal x-axis does not represent an instantaneous simultaneity between all points in space.
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Re: Photon's puzzle.

Postby BurtJordaan on September 27th, 2017, 10:49 am 

ralfcis » 27 Sep 2017, 14:16 wrote:Yes. as I stated in the previous post, I'm only talking about within an inertial frame. Setting all the clocks to the same time within that frame does not make them simultaneous unless you buy into how relativity defines simultaneity which involves Einstein's clock sync method.

There are other ways of synchronizing clocks (e.g. slow-transport), but in the end any valid method will leave them 'Einstein synchronized' in the specific inertial frame. Other, relatively moving frames will not agree that they are synchronized, so the sync'd clock concept is frame dependent. You know all this, so I don't quite understand what is bothering you.

Let me try this. Since you understand Epstein diagrams, you know that the Minkowski lightcone is 'fanned open' to cover the whole of the 2D space-propertime diagram. A flash of light at the origin spreads out in a circle, not only in space, but in space-propertime as a whole. Each relatively moving inertial frame's observers can however only observe the part of the expanding circle of light that spreads along their respective spatial axes. Just one of the many "puzzles of light", to paraphrase the OP title.

That 'expanding circle of light' represents equal clock readings for all inertial observers that have sync'd clocks at the origin as t=0. Since they were co-located, that event is obviously simultaneous for all of them. Now, from our "God's eye" perspective, where information takes no time to travel, let's read those clocks all simultaneously when they all show 1 sec. But do all the observers see that 'reading event' as simultaneous?

However much we would have loved it be so, the answer is no. They don't even see it as one event, but as different events happening at different places and at different times. Since we have no access to the "God's eye" perspective, we are forced to view things as we can observe them in real life, and it seems that the nearest thing to "God's eye" is "Einstein's eye". The usual reciprocal view of time dilation and Lorentz contraction between purely inertial frames.

Whether we use inertial frame clocks that were previously synchronized by the Einstein convention, or wait for light signals to be sent between the observers, the results remain the same. After all, the Epstein diagram is just a graphical view of the Lorentz transformations, which were observationally confirmed beyond all reasonable doubt.
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Re: Photon's puzzle.

Postby ralfcis on September 27th, 2017, 12:04 pm 

Ok, we're getting there. I just need time to think on your answer which looks good so far. Just one side note about slow-transport. It doesn't need to be slow if you know the twin paradox to get age difference. It's been long enough that it can be used as fact to solve problems rather than be considered fringe science. But maybe the slow transport gets you out of linearizing the accelerations involved in fast transport. These questions are coming out from my thread on explaining relative velocity to Dave.
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Re: Photon's puzzle.

Postby BurtJordaan on September 27th, 2017, 2:54 pm 

ralfcis » 27 Sep 2017, 18:04 wrote:Just one side note about slow-transport. It doesn't need to be slow if you know the twin paradox to get age difference.

No, 'fast-transport' cannot be used to synchronize clocks. The square of the relative speed must be negligible compared to c2, otherwise the two clocks will not end up synchronized. If you think differently, there is still a deep misunderstanding of the relativity of simultaneity and relativistic clock synchronization.

The 'twin-paradox' does not feature there. Please rethink what you wrote.
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