Can grandpa understand the Bell's Theorem?

[miosim]

Regardless of the mechanism, there is a "magic" result in QM that the observation of one of the two entangled particles effectively puts the other one into a pure state as given by that result. Although the initial state of the pair of particles can be described by probabilities, once an observation has been made, the state at the other end is known exactly, and the other particle behaves like one prepared with a precisely known state.

If the pure state (spin, polarization, etc.) of the other particle is known exactly and if this state isn’t included in the QM wave function the QM is incomplete. So we came back to EPR argument that, as I understand, wasn’t yet challenged directly. The best known indirect challenge is the Bell’s theorem that is based on the formal logic, algebra, and violates relativism.

 

[miosim]

I think that it is critical to understand how the photon passes the translucent media. If this is a series of collapses and reemergences (as JesseM suggested (if I understood him correctly)) the Aspect-like experiments cannot be interpreted as the influence over the distance between remotely placed targets, because entangled photons, as soon they are produced, are collapsing and loosing their entanglement by interacting with the optical media of the source.

To hold the existing interpretation of the Aspect-like experiment as influence over the distance we must to admit that the wave function of entangled photons doesn’t collapse whithin translucent media. Is it true?

 

[DrChinese]

I think that it is critical to understand how the photon passes the translucent media. If this is a series of collapses and reemergences (as JesseM suggested (if I understood him correctly)) the Aspect-like experiments cannot be interpreted as the influence over the distance between remotely placed targets, because entangled photons, as soon they are produced, are collapsing and loosing their entanglement by interacting with the optical media of the source.

To hold the existing interpretation of the Aspect-like experiment as influence over the distance we must to admit that the wave function of entangled photons doesn’t collapse whithin translucent media. Is it true?

No, no, no, it is not. You need to quit writing things which you simply make up as being factual, as I have told you previously.

Bell tests FIRST generate a proven entangled source by looking for perfect correlations at any angle. This is the definition of an entangled source. It does NOT matter about things like potential medium interactions the photons have as they travel, and in fact there are several specific ones that are actually planned in such experiments. But they do not affect the outcome as long as entanglement fidelity of the end stream is sufficient. That is how we know there is no collapse, it is experimentally demonstrated by examination of the resulting stream. It is called creating an EPR state. Period.

I realize you do not understand any of this, after all of the time we have tried to explain this. So I believe the answer to your original post is NO, grandpa cannot understand Bell.

(Hey, you win some, and you lose some. )

 

[harrylin]

Originally Posted by miosim:
"[..] To hold the existing interpretation of the Aspect-like experiment as influence over the distance we must to admit that the wave function of entangled photons doesn’t collapse whithin translucent media. Is it true?"

No, no, no, it is not. [..] That is how we know there is no collapse, it is experimentally demonstrated by examination of the resulting stream. It is called creating an EPR state. [..]

Are you sure that you actually read what he wrote?? Your answer after your "no" constitutes a "that's right, the wave function of entangled photons doesn’t collapse".

However, I had already given him a link to that fact... So it does appear that he "didn't get it".

 

[DrChinese]

Originally Posted by miosim:
"[..] To hold the existing interpretation of the Aspect-like experiment as influence over the distance we must to admit that the wave function of entangled photons doesn’t collapse whithin translucent media. Is it true?"Are you sure that you actually read what he wrote?? Your answer after your "no" constitutes a "that's right, the wave function of entangled photons doesn’t collapse".

... So it does appear that he "didn't get it".

He was essentially trying to say that it is an assumption, and that assumption could be challenged. But that is not the case. It is something which is demonstrated experimentally, and need not be assumed. And therefore cannot be challenged, since it is demonstrated.

miosim's (wrong) statement:

"the Aspect-like experiments cannot be interpreted as the influence over the distance between remotely placed targets, because entangled photons, as soon they are produced, are collapsing and loosing their entanglement by interacting with the optical media of the source."

He is trying to say that the experiment needs to be done in vacuum and with optical media that can be proven NOT to do anything to the photon. But that is flat wrong. In actuality, Bell tests use crystals, filters, wave plates, fiber optics and other things to move the photons to where they get into the polarizer/detector apparatus. That is perfectly legitimate and in no way alters the conclusion in and of themselves. Obviously, if the resulting entangled stream is of poor quality, that would be a different story. But then you couldn't get results rejecting local realism to such a high confidence level, currently much greater than 10 SD.

 

[miosim]

...However, I had already given him a link to that fact... So it does appear that he "didn't get it".

Don't worry I got it. According to your reference 'entanglement' is considered to be intact over a distance of 144 kilometers. And I have no problem with that.
So, if photons’ entanglement remains intact over long distance in the air this entanglement could be also preserved while photons are passing another translucent media – polarizer for example. However when I suggest an experiment that is based on this preservation of entanglement:

“…Using rotating polarizer we are changing the polarization of photons on one side while monitoring the polarization of entangled photons on other side…”

JesseM objected:

No, I already told you several times that the first measurement of each particle breaks the entanglement, after that the two photons are no more correlated than two non-entangled photons which happened to give the same two results to those first measurements…

So what does constitute the measurement and the wave function collapse? Is photon’s wave function collapses while it is passing a polarizer?

To demonstrate the inconsistency of JesseM response I pushed it to its limit and demonstrated that collapse of photon’s wave function, while it passes the translucent media, undermines all Aspect-like experiments and especially those that were conducted through the fibro optic media.

So my question is: does entangled photons that passed their respective polarizers remained entangled? Yes or No?
I would like to have a definite answear on this trivial question.

 

[SpectraCat]

Don't worry I got it. According to your reference 'entanglement' is considered to be intact over a distance of 144 kilometers. And I have no problem with that.
So, if photons’ entanglement remains intact over long distance in the air this entanglement could be also preserved while photons are passing another translucent media – polarizer for example. However when I suggest an experiment that is based on this preservation of entanglement:

“…Using rotating polarizer we are changing the polarization of photons on one side while monitoring the polarization of entangled photons on other side…”

JesseM objected:
So what does constitute the measurement and the wave function collapse? Is photon’s wave function collapses while it is passing a polarizer?

To demonstrate the inconsistency of JesseM response I pushed it to its limit and demonstrated that collapse of photon’s wave function, while it passes the translucent media, undermines all Aspect-like experiments and especially those that were conducted through the fibro optic media.

So my question is: does entangled photons that passed their respective polarizers remained entangled? Yes or No?
I would like to have a definite answear on this trivial question.

I believe that there is no simple answer to that question. The interaction with the polarizer breaks the polarization-entanglement, but does not completely collapse the state, as long as the photon has not been destructively detected. Rather, the individual photons become entangled (locally, I believe) with their respective measurement devices until one of the photons is detected. In fact, it has been shown experimentally that the entanglement can be transferred between pairs of photons using this method, by delaying detection and using the appropriate combinations of polarizers. I don't have the reference for the paper handy, but I think it is linked on Dr. Chinese's site .. it is one of the delayed choice quantum eraser (DCQE) papers.

So I think the answer to your question is, for the polarization-entangled photon pair (A,B), if A interacts with a polarizer, then it is no longer entangled with B (and vice-versa), but as long as neither have been destructively detected, then it may still be entangled with something else (e.g. a measurement device or another photon).

I should probably note that interaction with a traditional "one-way" polarizer, like a Polaroid filter, that will only pass one polarization, would count as destructive detection in the context of my comment. Interaction with a photon-counting device would obviously also count as destructive detection.

The polarizers I was thinking of are polarizing beam splitters (PBS's), which transmit both polarization states, but split them so they travel along different paths. That is why the entanglement can be transferred to such polarizers .. until you know which path the photon traveled along (i.e. by destructively detecting the photon), it's polarization state is entangled with the paths emerging from the beamsplitter, in analogous fashion to the double-slit experiment.

I haven't studied this stuff in detail for about a year, so I am a little rusty, but I think that my description above is essentially correct.

 

[DrChinese]

So my question is: does entangled photons that passed their respective polarizers remained entangled? Yes or No?
I would like to have a definite answear on this trivial question.

The general rule is no, they are no longer polarization entangled.

However, if you send them through wave plates (which rotate them), they remain polarization entangled. If you send them through polarizing beam splitters, and then recombine the stream so the which path information is erased, they will still be entangled (this is not easy to do however, more theoretical). If you use mirrors on them, they are still entangled.

I hope this helps.

 

[DrChinese]

To demonstrate the inconsistency of JesseM response I pushed it to its limit and demonstrated that collapse of photon’s wave function, while it passes the translucent media, undermines all Aspect-like experiments and especially those that were conducted through the fibro optic media.

I repeat, this is flat out wrong. There is nothing about the media per se - of which there are quite a number and I have enumerated many of these - that affects the results/conclusion of Bell tests. If the fidelity is too low, that could be a problem but that simply reduces the S value.

 

[miosim]

... So my question is: does entangled photons that passed their respective polarizers remained entangled? ...

The general rule is no, they are no longer polarization entangled.
However, if you send them through wave plates (which rotate them), they remain polarization entangled. If you send them through polarizing beam splitters, and then recombine the stream so the which path information is erased, they will still be entangled (this is not easy to do however, more theoretical). If you use mirrors on them, they are still entangled.

I hope this helps.

It helps a lot, because now I can propose the experiment that hopefully will directly prove the existence of an “influence over distance” in spirit of Bell’s theorem.

In this experiment we will rotate the polarization of one entangled photon in hope to observe the symmetrical rotation of another entangled photon.

We may start with the experimental setup very similar to Aspect’s, but with the polarized light source of entangled photons. We also will use two polarizers A and B set in parallel with each other and parallel with the light source polarization. However instead of correlation we will simply measure a light intensity on both sides.

Now, let’s place the wave plates (to rotate photon’s polarization) between light source and polarizer A. Because light beam that passes wave plates isn’t parallel any more to the polarizer A the intensity of the beam that passes this polarizer is changed according to Malus’ law.

If the light source is closer to the polarizer A (for the photon a to collapse first) we should observe the intensity of light at another side is changing in sync with side A that will be a direct proof of an “influence over distance”

What is your prediction of this experiment?

 

[Schrodinator]

20 pages?

Local realism is still not capable of predicting the results of quantum measurement right?

Inequalities still exist k and are violated. Just checking.

 

[Schrodinator]

It helps a lot, because now I can propose the experiment that hopefully will directly prove the existence of an “influence over distance” in spirit of Bell’s theorem.

In this experiment we will rotate the polarization of one entangled photon in hope to observe the symmetrical rotation of another entangled photon.

We may start with the experimental setup very similar to Aspect’s, but with the polarized light source of entangled photons. We also will use two polarizers A and B set in parallel with each other and parallel with the light source polarization. However instead of correlation we will simply measure a light intensity on both sides.

Now, let’s place the wave plates (to rotate photon’s polarization) between light source and polarizer A. Because light beam that passes wave plates isn’t parallel any more to the polarizer A the intensity of the beam that passes this polarizer is changed according to Malus’ law.

If the light source is closer to the polarizer A (for the photon a to collapse first) we should observe the intensity of light at another side is changing in sync with side A that will be a direct proof of an “influence over distance”

What is your prediction of this experiment?

Spooky action at a distance is what happens in experiment so it's kind of a pointless question. We've already showed that non local interactions in entangled systems occur, in fact its been shown so many times that the experiment itself now is kinda redundant, unless its for educational/instruction purposes there's probably not much point in flogging a dead horse.

We've also demonstrated that Bell's inequalities hold for almost all experiments and derivatives you can possibly imagine. Some would say this is not conclusive proof, but frankly the loop holes that people are coming up with now are getting pretty wild and speculative.

Holographic universes etc, it's really quite amusing really.

 

[harrylin]

20 pages?
Local realism is still not capable of predicting the results of quantum measurement right?

Don't worry, it took atomism hundreds (or thousands?) of years to predict the non-atomistic gas law

Inequalities still exist k and are violated. Just checking.

In case you overlooked it: it's still a matter of debate if that is even relevant.

 

[miosim]

Spooky action at a distance is what happens in experiment so it's kind of a pointless question…

You are right because QM is an empirical theory that isn’t in the business of explaining, but predicting only.

We've already showed that non local interactions in entangled systems occur, in fact its been shown so many times that the experiment itself now is kinda redundant, unless its for educational/instruction purposes there's probably not much point in flogging a dead horse …

According to Einstein only a theory “knows” what we observe during experiment. Regarding Aspect-like experiments they proved that correlation between entangled particle follow cos^2 (the same as Malus’ law). The interpretations of this result, as non local interactions, in my humble opinion, are based on

• Reading miscomprehension of the EPR (1935) paper
• Redefining the reality
• Formal logic and algebra

that eventually led to the violation of the respected relativistic theory.

I would be happy to collaborate my views on Bell’s theorem and related experiments in more details , but first …

… what did you say about prediction of the experiment in the post #310?

 

[DrChinese]

20 pages?

Local realism is still not capable of predicting the results of quantum measurement right?

Inequalities still exist k and are violated. Just checking.

I hear you. This discussion is sad, really. There are several folks here are sadly deluded into thinking there is an open debate on Bell in the scientific community (when there is none of substance). Actually, the biggest debate about Bell is whether he would have won the Nobel if he had not died somewhat prematurely.

 

[DrChinese]

It helps a lot, because now I can propose the experiment that hopefully will directly prove the existence of an “influence over distance” in spirit of Bell’s theorem.

In this experiment we will rotate the polarization of one entangled photon in hope to observe the symmetrical rotation of another entangled photon.

We may start with the experimental setup very similar to Aspect’s, but with the polarized light source of entangled photons. We also will use two polarizers A and B set in parallel with each other and parallel with the light source polarization. However instead of correlation we will simply measure a light intensity on both sides.

Now, let’s place the wave plates (to rotate photon’s polarization) between light source and polarizer A. Because light beam that passes wave plates isn’t parallel any more to the polarizer A the intensity of the beam that passes this polarizer is changed according to Malus’ law.

If the light source is closer to the polarizer A (for the photon a to collapse first) we should observe the intensity of light at another side is changing in sync with side A that will be a direct proof of an “influence over distance”

What is your prediction of this experiment?

The intensity stays the same at all times on both sides at all polarization angles, as I thought I had indicated previously. This is because an entangled stream consists of randomly polarized photons (actually a superposition of H and V so I am being loose in my language) and 50% of those will pass the polarizer at any orientation. Just as would occur with a stream in a mixed state, which by definition is random/unknown. (These states are indistinguishable unless coincidences are determined.)

Same is true when wave plates are added. No change in intensity with an entangled source. When particle A meets a wave plate, it does not change particle B in any way. And vice versa.

 

[miosim]

The intensity stays the same at all times on both sides at all polarization angles, as I thought I had indicated previously. This is because an entangled stream consists of randomly polarized photons...

I agree with you that the intensity stays the same at all times on both sides at all polarization angles if an entangled stream consists of RANDOMLY POLARIZED photons.
However, the key requirement for the proposed in the post #310 experiment is that the light source consists not of RANDOMLY POLARIZED photons, but is a polarized light that consists of POLARIZED ENTANGLED PHOTONS. I probably should emphasize this critical condition. My bad.

Could you please provide your prediction for this experiment taking in account my clarification?

Thank you

 

[DrChinese]

I agree with you that the intensity stays the same at all times on both sides at all polarization angles if an entangled stream consists of RANDOMLY POLARIZED photons.
However, the key requirement for the proposed in the post #310 experiment is that the light source consists not of RANDOMLY POLARIZED photons, but is a polarized light that consists of POLARIZED ENTANGLED PHOTONS. I probably should emphasize this critical condition. My bad.

Could you please provide your prediction for this experiment taking in account my clarification?

Thank you

If they are polarization entangled, then they are not polarized. They are in a superposition of polarization states. (By definition.) They will not be entangled as to polarization if you know their polarization.

They could be polarized but NOT entangled as to polarization, is that what you mean? You get that from a single Type I PDC crystal. If so, the intensity will simply follow Malus. Of course, these will not meet the criteria of EPR (i.e. their polarizations will not lead to perfect correlations).

 

[DrChinese]

...

If the light source is closer to the polarizer A (for the photon a to collapse first) we should observe the intensity of light at another side is changing in sync with side A that will be a direct proof of an “influence over distance”

What is your prediction of this experiment?

Just to be clear: there is no setup in which a change in A leads to a change in intensity at B. This is true regardless of the ordering of arrival at the polarizers.

 

[miosim]

If they are polarization entangled, then they are not polarized. They are in a superposition of polarization states. (By definition.) They will not be entangled as to polarization if you know their polarization

As I understood you correctly, it is theoretically impossible to produce the light source of entangled protons that will behave as polarized light during interaction with polarizer. I would like to better understand this phenomenon. Can you please explain the difference between a photon of polarized light and the entangled photon from the QM wave function point of view?

Thanks

 

[SpectraCat]

As I understood you correctly, it is theoretically impossible to produce the light source of entangled protons that will behave as polarized light during interaction with polarizer. I would like to better understand this phenomenon. Can you please explain the difference between a photon of polarized light and the entangled photon from the QM wave function point of view?

Thanks

If you have a polarized photon it is in a state of definite polarization, i.e. either |H> or |V> ... those are the basis states for polarization. A polarization-entangled photon is in a superposition state, e.g. 0.707(|H> + |V>) or 0.707(|H> -|V>). Thus when a stream of polarization-entangled photons interacts with a polarization sensitive detector, half of the time the |H> state is registered, and the other half of the time the |V> state is registered. That is why DrC told you that you would see 50% intensity in both beams (for ideally efficient instrumentation) in the example you asked about earlier. Rotating the polarization of one beam prior to detection makes no difference. You can think of that as changing the basis to |H'> and |V'>, but now half the photons will be detected in |H'> and the other half in |V'>, so the intensity is still 50%.

 

[DrChinese]

As I understood you correctly, it is theoretically impossible to produce the light source of entangled protons that will behave as polarized light during interaction with polarizer. I would like to better understand this phenomenon. Can you please explain the difference between a photon of polarized light and the entangled photon from the QM wave function point of view?

Thanks

SpectraCat said it nicely above. To that I would add:

The state of an individual photon can be either known (pure, which occurs when it passes a polarizer or is produced coherently such as from a laser) or a superposition (entangled). However, a photon polarized at 45 degrees can rightfully be considered a superposition of H and V as well. It is impossible to experimentally distinguish that from an entangled photon on the H/V basis (without resorting to coincidence counting). Further, you could have a group of photons in unknown but pure states (i.e. a statistical distribution). Those are similarly indistinguishable on the H/V basis. And yet all of these streams have somewhat different properties in other bases.

 

[San K]

SpectraCat said it nicely above. To that I would add:

However, a photon polarized at 45 degrees can rightfully be considered a superposition of H and V as well. It is impossible to experimentally distinguish that from an entangled photon on the H/V basis (without resorting to coincidence counting).

how would you distinguish (between 45 and entangled photon) via co-incidence counting?

the photon polarized at 45 degree would not give the exact opposite spin? but the entangled photon would?

 

[SpectraCat]

how would you distinguish (between 45 and entangled photon) via co-incidence counting?

the photon polarized at 45 degree would not give the exact opposite spin? but the entangled photon would?

Yes .. if you have two entangled photons, and you compare coincidence counts for them against coincidence counts for unentangled photons with 45 degree polarization, you will find that the entangled photons show coincidence counts with a certain degree of correlation (you can make it theoretically perfect if you choose the detector angles appropriately), whereas the unentangled are uncorrelated (i.e. random coincidences). It takes some work, but this is essentially the control experiment that folks like Aspect and Zeilinger run to make sure they have entangled photons for their experiments.

 

[San K]

Yes .. if you have two entangled photons, and you compare coincidence counts for them against coincidence counts for unentangled photons with 45 degree polarization, you will find that the entangled photons show coincidence counts with a certain degree of correlation (you can make it theoretically perfect if you choose the detector angles appropriately), whereas the unentangled are uncorrelated (i.e. random coincidences). It takes some work, but this is essentially the control experiment that folks like Aspect and Zeilinger run to make sure they have entangled photons for their experiments.

thanks spectracat...i am reading up on coincidence counter on Wikipedia...

spectraCat wrote "coincidence counts with a certain degree of correlation" ...correlated via timing or quantum state (i.e. spin?) or both?

 

[miosim]

I would like to try another Gedanken Experiment.
Say we have the classical Aspect experiment with both polarizers set in parallel (is it antiparallel?) to achieve the 100% correlation.
Now let’s insert one wave plate at any side between photon source and the polarizer to rotate photon’s polarization on this side by 90 degree. As I understand, according to Bell paradigm the result of the Aspect’s experiment shouldn’t change because both entangled photons exibit the same antiparallel polarization. However according to EPR paradigm the polarization between both entangled photons will be shifted by 90 degree and the Aspect experiment should yield zero correlation.

Does it make sense?

 

[DrChinese]

I would like to try another Gedanken Experiment.
Say we have the classical Aspect experiment with both polarizers set in parallel (is it antiparallel?) to achieve the 100% correlation.
Now let’s insert one wave plate at any side between photon source and the polarizer to rotate photon’s polarization on this side by 90 degree. As I understand, according to Bell paradigm the result of the Aspect’s experiment shouldn’t change because both entangled photons exibit the same antiparallel polarization. However according to EPR paradigm the polarization between both entangled photons will be shifted by 90 degree and the Aspect experiment should yield zero correlation.

Does it make sense?

Yes, it makes sense. But you label the outcomes incorrectly. Inserting a 90 degree wave plate on Alice's side makes the correlations go from 100% to 0%. This is the QM prediction.This does not collapse the wave function, it just rotates the polarization on that side ONLY. Doing something to one does not cause the same action to occur on the other. However: learning something about one causes us to learn something about the other within the limits of the HUP.

 

[miosim]

...Inserting a 90 degree wave plate on Alice's side makes the correlations go from 100% to 0%. This is the QM prediction. This does not collapse the wave function, it just rotates the polarization on that side ONLY...

But what happens when the wave function collapses? Where is the “action over the distance” that according to QM and Bell paradigm must produce antiparallel polarization and 100% correlation?

It seems to me that this Gedanken Experiment refutes QM and Bell paradigms and embraces EPR argument.

 

[DrChinese]

But what happens when the wave function collapses? Where is the “action over the distance” that according to QM and Bell paradigm must produce antiparallel polarization and 100% correlation?

They are still correlated after the wave plate, because the wave function has not collapsed. The collapse occurs when we finally learn something definite about one or the other. Actually the collapse occurs as the number of outcomes is restricted, ultimately down to one in the typical case.

The action at a distance, if there is such, is that what is measured at point A restricts the outcomes at point B to those that are compatible.

 

[miosim]

They are still correlated after the wave plate, because the wave function has not collapsed. The collapse occurs when we finally learn something definite about one or the other. Actually the collapse occurs as the number of outcomes is restricted, ultimately down to one in the typical case.

The action at a distance, if there is such, is that what is measured at point A restricts the outcomes at point B to those that are compatible.

So, if the correlated photons are remained entangled after the wave plate and the outcome at point A restricts the outcomes at point B -- that means that both photons will exhibit the anntiparalel polarization. This means that QM and Bell’s paradigm should predict 100% correlation while EPR paradigm predicts 0% correlation.

This is the very simple Gedanken Experiment and I don't expect an ambiguous prediction and explanation.