Mind over matter reality or myth?

[adfreeman]

Hi, I’m new to the forum and I would like to ask some questions. I’m not a physicist –for some reason that I’ll always regret I chose Business Studies- and my knowledge of physics is limited to high school, physics books and documentaries; which I must have watched them all by now.

Anyway, for many years I’ve been intrigued by the same issues that Einstein had with quantum physics -for example, nonlocality, quantum entanglement, the observer effect (commonly confused with the uncertainty principle), and so on and so forth- so I would appreciate if anyone could help me solve my doubts.

The first issue, which is the simplest, is the observer effect on the double slit experiment. Every single physicist that I saw explaining the double slit experiment -Brian Green, Michio Kaku, Neil deGrasse Tyson, and so on- reaches a point where he says that the observer is influencing the particles. For example: this is a literal quote from the first video about it that I found on YouTube “Dr Quantum –Double Slit Experiment”:

“The particle behaved differently, because it was aware that it was been watched.”
​

First of all, I think all these documentaries and physicists are confusing a lot of people with these claims and are creating a lot of controversy; as this is not the case: neither we can see the particles traveling through the double slit, nor the particle cares whether anyone is watching or not, and therefore our consciousness has no influence on the experiment. I just checked in the Wikipedia for curiosity, and at least they got it right: the observer refers to an instrument, not a person.

In any case, the experiment shows that if we do not try to find out through which slit the particle passed, it behaves as a wave, passing through both slits, and create an interference pattern; but if we try to determine it, then it behaves as a particle, and passes just through one slit. Now, my question is: doesn’t this mean that the equipment that is detecting the path of the particles is interfering with them, and therefore preventing it from passing through both slits and creating the interference pattern? If this is the case, what is all the fuzz then? Is it all because of those who claim the observer is a person, and therefore give the impression that physicist are claiming that mind over matter is a fact?

I’ll post the rest latter. Thanks for your help.

 

[jfizzix]

One way I like to look at the double slit experiment is to take a step back and describe the particles and measurement device together quantum mechanically. What you find is that the interaction of the device with the particles destroys the coherence between the different paths, and you see no interference pattern.

If you make this interaction weak, so that the measurement device only has a little information about which slit the particle went through, you find the interference pattern is not quite as clear as it would be if there were no interaction. As the interaction strength grows, the visibility of the interference pattern gets worse, until with maximum information, you have zero visibility.

 

[Jason Debus]

Hi adfreeman, I'm new to this forum and have been asking a similar question for the last couple of years. To get to the heart of the matter, it the KNOWLEDGE of which path, or slit. A more modern version of the experiment:



Sean Carroll talking about the different interpretations:



Hope this helps, I know it did for me.

 

[adfreeman]

One way I like to look at the double slit experiment is to take a step back and describe the particles and measurement device together quantum mechanically. What you find is that the interaction of the device with the particles destroys the coherence between the different paths, and you see no interference pattern.

If you make this interaction weak, so that the measurement device only has a little information about which slit the particle went through, you find the interference pattern is not quite as clear as it would be if there were no interaction. As the interaction strength grows, the visibility of the interference pattern gets worse, until with maximum information, you have zero visibility.

Thanks for the reply.

Could it be that in your example "weak" means that not all particles interfere with the measuring device; therefore some don't interact at all, and pass through both slits, and the rest interact with the device, and therefore just pass through one or the other slit?

 

[adfreeman]

Hi adfreeman, I'm new to this forum and have been asking a similar question for the last couple of years. To get to the heart of the matter, it the KNOWLEDGE of which path, or slit. A more modern version of the experiment:

...

Hope this helps, I know it did for me.

Thanks for the reply and the videos.

You might also be interested in reading this other thread I found: Observation and its role on objects/matter/particles

 

[Nugatory]

The first issue, which is the simplest, is the observer effect on the double slit experiment. Every single physicist that I saw explaining the double slit experiment -Brian Green, Michio Kaku, Neil deGrasse Tyson, and so on- reaches a point where he says that the observer is influencing the particles. For example: this is a literal quote from the first video about it that I found on YouTube “Dr Quantum –Double Slit Experiment”:

"Every single physicist"? The three you have listed (I'm not counting Dr Quantum because I don't think he is a real physicist or even entitled to call himself "Dr" - no record of anyone by that name ever having received a doctoral degree from any reputable school) are pretty much the only contemporary physicists saying that. And they aren't saying it in any of their serious work, just in their pop-sci stuff which is intended to entertain rather than to inform.

First of all, I think all these documentaries and physicists are confusing a lot of people with these claims and are creating a lot of controversy; as this is not the case: neither we can see the particles traveling through the double slit, nor the particle cares whether anyone is watching or not, and therefore our consciousness has no influence on the experiment. I just checked in the Wikipedia for curiosity, and at least they got it right: the observer refers to an instrument, not a person.

Yep... We spend a fair amount of time here trying to unconfuse people who have been confused by this stuff.

In any case, the experiment shows that if we do not try to find out through which slit the particle passed, it behaves as a wave, passing through both slits, and create an interference pattern; but if we try to determine it, then it behaves as a particle, and passes just through one slit. Now, my question is: doesn’t this mean that the equipment that is detecting the path of the particles is interfering with them, and therefore preventing it from passing through both slits and creating the interference pattern? If this is the case, what is all the fuzz then? Is it all because of those who claim the observer is a person, and therefore give the impression that physicist are claiming that mind over matter is a fact?

No, there's more to it than that. If you send your quantum particles towards the two slits one at a time, each particle will produce a single dot on the photographic film just as you'd expect a proper and well-behaved classical particle would. However, over time these dots will build up an interference pattern - even though the dots are produced one at a time, many seconds apart. That behavior is inconsistent with our classical notions of both waves and particles, and tells us that quantum objects are fundamentally and interestingly different from anything in the macroscopic world. That's a big deal even without the drivel about mind over matter.

 

[A. Neumaier]

Is it all because of those who claim the observer is a person, and therefore give the impression that physicist are claiming that mind over matter is a fact?

In modern quantum experiments such as the colliders at CERN or experiments done using photodetection, all observers are mindless machines. People only look at the final statistics produced by fully automatic computer programs that process the information from fully automatic recordings of the observations. Nothing ever involves mind or consciousness, except interpreting the final statistics.

 

[adfreeman]

"Every single physicist"? The three you have listed (I'm not counting Dr Quantum because I don't think he is a real physicist or even entitled to call himself "Dr" - no record of anyone by that name ever having received a doctoral degree from any reputable school) are pretty much the only contemporary physicists saying that. And they aren't saying it in any of their serious work, just in their pop-sci stuff which is intended to entertain rather than to inform.

Yes, of course, it's not "every single physicist" in the world. What I said was "every single physicists I saw explaining the experiment".

No, there's more to it than that. If you send your quantum particles towards the two slits one at a time, each particle will produce a single dot on the photographic film just as you'd expect a proper and well-behaved classical particle would. However, over time these dots will build up an interference pattern - even though the dots are produced one at a time, many seconds apart. That behavior is inconsistent with our classical notions of both waves and particles, and tells us that quantum objects are fundamentally and interestingly different from anything in the macroscopic world. That's a big deal even without the drivel about mind over matter.

Yes, I understand all that and I also find the experiment fascinating. But what I meant to ask is: isn't it clear that it's the particles interfering with the slit detector that prevents them from forming the interference pattern?

In modern quantum experiments such as the colliders at CERN or experiments done using photodetection, all observers are mindless machines. People only look at the final statistics produced by fully automatic computer programs that process the information from fully automatic recordings of the observations. Nothing ever involves mind or consciousness, except interpreting the final statistics.

Yes, that's what I thought; however, in all these documentaries they literally say that it is the observer that's influencing the result, which gives the impression to many people that by observer they mean a conscious mind.

 

[A. Neumaier]

in all these documentaries they literally say that it is the observer that's influencing the result, which gives the impression to many people that by observer they mean a conscious mind.

That impression is created on purpose by those writing for the general public because it is the stuff that makes quantum stories sell to the public at large. It has its precedents in the early days of quantum mechanics when it was not yet clear how quantum mechanics could be understood most rationally, so that even famous physicists played gedanken experiments involving consciousness to find out the limits of the theory. Since it is this speculative part that is most easily communicated to lay people, and since people at large expect quantum physics to be a kind of magic, popular accounts are heavily colored by it. But whoever wants to get serious about understanding quantum mechanics must first get rid of all this magical talk about it.

 

[PeroK]

Yes, that's what I thought; however, in all these documentaries they literally say that it is the observer that's influencing the result, which gives the impression to many people that by observer they mean a conscious mind.

I found this quotation recently:

"On the surface, an intelligible lie; underneath, the unintelligible truth."

Perhaps the popular science presenters have no choice but to present an intelligible lie.

 

[Nugatory]

Yes, I understand all that and I also find the experiment fascinating. But what I meant to ask is: isn't it clear that it's the particles interfering with the slit detector that prevents them from forming the interference pattern?

That line of thinking is a huge improvement over the stuff in those videos (which should be treated as entertainment, not education).

There's more to it than just the interaction with the detector though. Some interactions will kill the interference pattern when others won't; for example if we place polarizing filters behind the slits (with no other detectors) we'll get an interference pattern when the fileters are aligned parallel but not when they're aligned at right angles. And in some delayed choice experiments (the wikipedia section on Kim's delayed choice quantum eraser is decent) we get an interference pattern or not according to whether the particle had two paths available to it or not - even though the particles undergo the exact same interaction with the slits in both cases.

 

[Nugatory]

I found this quotation recently:
"On the surface, an intelligible lie; underneath, the unintelligible truth."
Perhaps the popular science presenters have no choice but to present an intelligible lie.

There are enough examples of good popularizations, even in quantum mechanics, that I don't see the need to accept bad ones. Simplification is unavoidable, and without the mathematical formalism there's no way of being precise... But we can simplify without misleading the way that Dr Quantum does.

 

[adfreeman]

That impression is created on purpose by those writing for the general public because it is the stuff that makes quantum stories sell to the public at large. It has its precedents in the early days of quantum mechanics when it was not yet clear how quantum mechanics could be understood most rationally, so that even famous physicists played gedanken experiments involving consciousness to find out the limits of the theory. Since it is this speculative part that is most easily communicated to lay people, and since people at large expect quantum physics to be a kind of magic, popular accounts are heavily colored by it. But whoever wants to get serious about understanding quantum mechanics must first get rid of all this magical talk about it.

There are enough examples of good popularizations, even in quantum mechanics, that I don't see the need to accept bad ones. Simplification is unavoidable, and without the mathematical formalism there's no way of being precise... But we can simplify without misleading the way that Dr Quantum does.

I realize they have to make physics entertaining, especially since science is not very popular in the world we live in. But what they are doing is exaggerating the analogies so much, that they stop being true; they are practically lying on purpose to the public. And I'm not referring to the Dr. Quantum and such, which I just chose because it was short and to the point, I'm referring to top scientists like the ones previously mentioned, or for example, Alex Filippenko in the science documentary "The Universe" from PBS, who literally says in the episode "Microscopic Universe" while explaining the double slit experiment:

"... when my eyes are closed, it behaves like a wave. But then, at the last second, before it hits the screen I open my eyes and decide to observe it." And the narrator continues: "At that moment, the electrons in essence, become particles."​

No wonder there are a lot of quacks out there claiming that now quantum physics confirms all sorts of paranormal claims. I don't think going to such extremes does any good to anyone, as it creates a lot of confusion.

 

[adfreeman]

That line of thinking is a huge improvement over the stuff in those videos (which should be treated as entertainment, not education).

There's more to it than just the interaction with the detector though. Some interactions will kill the interference pattern when others won't; for example if we place polarizing filters behind the slits (with no other detectors) we'll get an interference pattern when the fileters are aligned parallel but not when they're aligned at right angles. And in some delayed choice experiments (the wikipedia section on Kim's delayed choice quantum eraser is decent) we get an interference pattern or not according to whether the particle had two paths available to it or not - even though the particles undergo the exact same interaction with the slits in both cases.

Yes, I was planning on getting into the polarizing filters latter on when I ask about the Aspect experiment in Paris for the Bell tests; which I'm still researching a bit more.

 

[PeroK]

There are enough examples of good popularizations, even in quantum mechanics, that I don't see the need to accept bad ones. Simplification is unavoidable, and without the mathematical formalism there's no way of being precise... But we can simplify without misleading the way that Dr Quantum does.

You're perhaps being a little unfair on poor Dr Quantum. The last science programme I tried to watch on QM on British TV was presented by Jim Al-Khalili (and he's a real physicist, I believe). After 15 minutes he'd said nothing beyond a vague description of the photo-electric effect and I left him sipping a cocktail in a 1920's jazz bar. And that was BBC4!

 

[entropy1]

I feel I might have to chip in my two cents I watched Dr. Quantum, and I find it, along with almost all popularisations of quantum physics on TV (+Youtube), incredibly superficial and even misleading. I have to say I am very annoyed by such misinformation of the unsuspecting public! And even I am a layman!

 

[Nugatory]

You're perhaps being a little unfair on poor Dr Quantum. The last science programme I tried to watch on QM on British TV was presented by Jim Al-Khalili (and he's a real physicist, I believe). After 15 minutes he'd said nothing beyond a vague description of the photo-electric effect and I left him sipping a cocktail in a 1920's jazz bar. And that was BBC4!

You mean it's even worse than I thought?!

 

[bhobba]

No wonder there are a lot of quacks out there claiming that now quantum physics confirms all sorts of paranormal claims. I don't think going to such extremes does any good to anyone, as it creates a lot of confusion.

Even in the standard beginner textbooks on QM many myths are perpetuated:
http://arxiv.org/abs/quant-ph/0609163

I am not 100% sure the full monty can be given at the beginner level. Because of that I cut a fair amount of slack in these treatments. My issue however is in the books at the intermediate level. They don't go back and correct these misconceptions, somehow expecting students to pick up when things have changed. As far as the double slit goes here is a good intermediate treatment:
http://arxiv.org/ftp/quant-ph/papers/0703/0703126.pdf

But just to show a proper understanding of QM is not that easily won, even the above is incorrect when viewed from a more advanced viewpoint:
http://arxiv.org/abs/1009.2408

Unfortunately QM seems to be one of those areas you need to constantly unlearn things as you progress. It seems to be the nature of the beast.

Personally I think a whole new approach is required such as the following:
http://www.scottaaronson.com/democritus/lec9.html

But we have quite a few people that actually teaches this stuff posting here (I am not one) and they are not sure such an approach is the answer either. So who knows.

Thanks
Bill

 

[jfizzix]

Thanks for the reply.

Could it be that in your example "weak" means that not all particles interfere with the measuring device; therefore some don't interact at all, and pass through both slits, and the rest interact with the device, and therefore just pass through one or the other slit?

It's possible, that one could have an interaction where particles in one set of quantum states interact, and particles in another set do not, say, if the interaction works only is the spin of the particles is in a particular state, and if the weakness is controlled by a slight polarization rotation into that ideal state.
The tradeoff between which-path information and fringe visibility is more general than that, though (it is in fact an exotic variety of quantum uncertainty relation), so this particular example would only be a special case.

 

[adfreeman]

I just finished watching this documentary for the Nth time; it's about Bohr and Einstein's argument regarding entangled particles transmitting information faster than the speed of light, which seemed to prove Bohr right when Alain Aspect carried out in an experiment John Bell's inequality tests.



(The experiment is explained in minute 24:55 of the video)

In the experiment, they produce 2 entangled photons with lasers from a calcium atom; which they found out have the same polarization, as they only passed through both polarized filters when they were in the same orientation -which I guess is also why in the double slit experiment that Nugatory mentioned in post #11 the polarization filters must be in the same orientation for the interference pattern to form. Then they needed to find out if the entangled particles had the same polarization from the beginning, as Einstein though -as well as me-, or if they acquired that property later on, as Bohr believed. So they built something like this to test it:

The entangled particles travel from the cylindrical chamber in the center, along the tubes, passing through one of 2 polarized filters with opposite orientations, which is decided by their respective switch. The switches change faster than the time needed for any information to travel between photos at the speed of light. Now, on the documentary they say that even in these conditions the photons have the same polarization, but, even though I watched it a dozen times, I don't think they clear how that was proved. I mean, if the particles still have the same polarization after the switches, how does that prove that they did not have it from the very beginning. It's not like the switches are changing any property on the particles, just changing their direction, and therefore the polarized filter they will pass through. Isn't it?

Can anyone please explain it? Thanks

 

[adfreeman]

By the way, is the polarization of the photons determined or related to their spin; or is it a different property?

 

[Nugatory]

how does that prove that they did not have it from the very beginning?

Start a new thread for that - it's a whole new question. But before you do, take a look at some of what has already been written:
https://www.scientificamerican.com/media/pdf/197911_0158.pdf
http://www.drchinese.com/Bells_Theorem.htm (maintained by a PF regular)

And there are many many threads here as well.

 

[adfreeman]

Start a new thread for that - it's a whole new question. But before you do, take a look at some of what has already been written:
https://www.scientificamerican.com/media/pdf/197911_0158.pdf
http://www.drchinese.com/Bells_Theorem.htm (maintained by a PF regular)

And there are many many threads here as well.

Thanks, the first looks to advance for me, but the second link seems fine -at least I can't see any formulas. By the way, are there no short answers to my question?

 

[Nugatory]

Thanks, the first looks to advance for me, but the second link seems fine -at least I can't see any formulas. By the way, are there no short answers to my question?

Don't give up on that Scientific American article too quickly. It has formulas, but they're just simple counting formulas, basically working through variations on the idea that the number of left-handed smokers in a room has to be less than or equal to the number of left-handed women plus the number of men who smoke.

There are a good short answers in some of the other threads here. The assumption that the particles had the property from the beginning leads to different statistical correlations than QM makes, and the Aspect-type experiments are measuring the correlations to see which we're getting.

 

[adfreeman]

The assumption that the particles had the property from the beginning leads to different statistical correlations than QM makes, and the Aspect-type experiments are measuring the correlations to see which we're getting.

Yes, I realized that; as it is explained in the documentary. What they don't explain, and what I needed to know, is exactly how that experiment proves it.

Thanks anyway, I'll read the articles and look for related threads.

 

[entropy1]

working through variations on the idea that the number of left-handed smokers in a room has to be less than or equal to the number of left-handed women plus the number of men who smoke.

I want to thank you, for this is now the first time I think I get Bell's theorem! Thanks!

 

[adfreeman]

I want to thank you, for this is now the first time I think I get Bell's theorem! Thanks!

Have you seen this (jump to minute 5:27)

 

[entropy1]

Have you seen this (jump to minute 5:27)

I will probably have to watch that video several times to be able to understand it.

 

[adfreeman]

I will probably have to watch that video several times to be able to understand it.

Same here -I just found it-

And I'll probably have to ask once I get it; as learning something generates more questions in my head than it solves.

 

[adfreeman]

I will probably have to watch that video several times to be able to understand it.

This video reminded me of you; you'll probably going to like it.



If you are interested in physics, watch the other videos from that guy; some of them blew me away.

 

[Mark Harder]

I found this quotation recently:

"On the surface, an intelligible lie; underneath, the unintelligible truth."

Perhaps the popular science presenters have no choice but to present an intelligible lie.

I wouldn't know how to do it well, but I think that truly talented popular science presenters can delve into the depths in a way that intelligent, curious audiences can understand. The exposition would leave out as much math as possible and only retain those equations that can be described: We have the energy on one side of the equation and the mass, which can vary, times the constant speed of light, multiplied by itself. "The equation says that mass and energy are equivalent and it gives us a way to calculate how much energy will be created when so much matter is destroyed." Well, I'm not that talented, but that's the idea, I think. Some science presentations don't even try to explain, and that's OK. Whiz-bang visual effects via video or animation can provoke interest in the subject matter without a lot of explanations, specious or otherwise. Since the goal is to provoke curiosity and wonder, that often suffices. Last night I watched a documentary in which David Suzuki presented some recent developments in the study of sound. Some of the experimental effects were really cool. Even I wondered if I could create a science fair project like some of them.

 

[bhobba]

how does that prove that they did not have it from the very beginning.

It doesn't:
http://www.drchinese.com/Bells_Theorem.htm

But it requires another thread.

Thanks
Bill

 

[adfreeman]

It doesn't:
http://www.drchinese.com/Bells_Theorem.htm

But it requires another thread.

Thanks
Bill

I think I understand Bell's inequality and what went on in Aspect's experiment; if "I understand" is a valid term for a layman to say about QM.

The problem is that solving that doubt has generated a dozen more. But since I titled this thread incorrectly, and only applies to my first doubt -instead of all the doubts I had regarding this subject- it might be best if I ask them somewhere else in the forum; as you have suggested.

 

[Bruno81]

What is mind? No matter. What is matter? Never mind.

Btw, you unlearning pop sci accounts of quantum experiments is easy, you'll get it right in little time. Ask the physicists about unlearning to think classically.

 

[Hornbein]

Last night I watched a documentary in which David Suzuki presented some recent developments in the study of sound. Some of the experimental effects were really cool. Even I wondered if I could create a science fair project like some of them.

You've got me curious. Care to start a thread about it? I bet it is those experiments where they record sound on a boundary. They then reproduce that sound at the boundary, inverting the wave and focusing the energy at the original source.

 

[quarknsoul]

I think brain waves probably disturbed the wave function. Human's brain can make electromagnetic field, do you think?

 

[bhobba]

I think brain waves probably disturbed the wave function. Human's brain can make electromagnetic field, do you think?

Then you think wrong. The EM field of the brain can't do that. It happens whether a human being is there or not.

Thanks
Bill

 

[Mark Harder]

You've got me curious. Care to start a thread about it? I bet it is those experiments where they record sound on a boundary. They then reproduce that sound at the boundary, inverting the wave and focusing the energy at the original source.

No, I don't think the boundary story to which you refer is included. As I recall there are a couple of demos using white powder to indicate nodes on vibrating surfaces. In one of these, they used a violin bow to show how patterns of vibrational nodes change with changes in sound intensity. There are also demos of electrically stimulated plates doing the same thing. Maybe that's what you mean. There are also videos of small objects suspended in 3D nodes in a body of air.

 

[adfreeman]

Then you think wrong. The EM field of the brain can't do that. It happens whether a human being is there or not.

Thanks
Bill

I've been reading and watching documentaries about Bell's inequality and the Aspect experiments, and I have the hunch that at least one of the experiments might have to do with what happens in the double slit experiment.

In one of the experiments, which I find quite curious, photos are stopped when 2 consecutive polarization filters at 90 degrees are used; for example, if you put a polarized filter in the horizontal position, and then another in the vertical position, no photos will pass both filters. However, if between those 2 filters you add a third polarized filter at 45 degrees, or diagonal to the other 2, then most of the photon will pass (don't remember the exact percentage). Therefore, would it be reasonable to assume that polarization filters are interfering with the photons, or changing / modifying some of their properties; like polarization or spin?

 

[bhobba]

Therefore, would it be reasonable to assume that polarization filters are interfering with the photons, or changing / modifying some of their properties; like polarization or spin?

Sure.

Thanks
Bill

 

[adfreeman]

Sure.

You mean it like:

Sure... it's known already that the polarization filters are interfering / modifying properties on the photons?

or

Sure... it's possible, though we still don't know. In which case, would this be... kind of a big deal?

 

[bhobba]

Sure... it's known already that the polarization filters are interfering / modifying properties on the photons?

Of course:
http://alienryderflex.com/polarizer/

If you want to disuses these or similar experiments start a new thread.

Thanks
Bill

 

[adfreeman]

Thanks Bill,

I'll open a new thread. But can I ask a last question before I do?

Where does this formula comes from:

( cos(degrees of polarized filter difference) )²​

It's the one used in Bell's inequality to predict the results according to QM; for example:

( cos(120 deg) )² = 0.25 or 1/4​

I'm asking, who came up with it, and how?

 

[bhobba]

( cos(degrees of polarized filter difference) )²​

These things are easy to look up:
http://www.physicshandbook.com/laws/maluslaw.htm

Thanks
Bill

 

[Nugatory]

Therefore, would it be reasonable to assume that polarization filters are interfering with the photons, or changing / modifying some of their properties; like polarization or spin?

Yes, that is what is happening with the polarization (not spin here - that's a different property). The interaction with the first filter collapses the wave function of the surviving photons into the horizontally polarized state. This state is a superposition of 45-degree and 135-degree polarization (a calculation that we wouldn't bother with except that we know we're about to be asked about what happens when these photons reach the second filter). The collapse at the second filter leaves the surviving photons in the 45-degree polarized state; this state is a superposition of horizontal and vertical so some of them will pass the third filter and collapse to the vertical state. If we didn't have the 45-degree filter in the middle, we'd be passing the horizontally polarized photons from the first filter directly to the vertical filter, and nothing would pass.

(don't remember the exact percentage)

It's 50% of the photons that made it past the first filter, if the angle is exactly 45 degrees. This is intuitively reasonable from the symmetry of the situation (would you expect the result to change if we turned the experimental apparatus on its side?) or you can calculate it by writing $|H\rangle=\frac{\sqrt{2}}{2}(|45\rangle+|135\rangle)$ where H, 45, and 135 are the states that have 100% probability of passing through horizontal, 45-degree, and 135-degree filters respectively.

The connection with Bell's theorem and Aspect-type experiments is somewhat tenuous though (except that this is basic QM required as background before you dig into those topics). There are local hidden variable explanations for the behavior of single photons passing through polarizing filters.

 

[entropy1]

Therefore, would it be reasonable to assume that polarization filters are interfering with the photons, or changing / modifying some of their properties; like polarization or spin?

Of circular polarized photons, ½ gets trough. Of polarized photons, cos²(α) gets through. If you put circular polarized photons through a polarizer, they get polarized, and a following polarizer passes cos²(α).

 

[Nugatory]

These things are easy to look up:
http://www.physicshandbook.com/laws/maluslaw.htm

It is indeed Malus's law, but the history may be confusing. Early in the 19th century, Etienne Malus observed that if you passed light through two consecutive polarizing filters at an angle $\alpha$, the fraction of light that passed the second filter would be given by $\cos^2\alpha$ and this is Malus's law. He had no explanation for this phenomenon, it was just an observed fact (and given what was known about the nature of light at the time, this is all that could be expected).

In 1861 James Maxwell discovered the equations of classical electrodynamics and that light was electromagnetic radiation obeying those equations. Malus's law can be derived from these equations, so classical physics had an explanation for what had previously been an empirically observed but unexplained phenomenon.

Quantum electrodynamics, developed during the second quarter of the 20th century, introduced the notion of photons and showed that individual photons would display the same $\cos^2\alpha$ behavior. On the one hand, this result is completely unsurprising; the easiest way of explaining how a many-photon light beam would be attenuated in this way is to assume that the individual photons behave that way. On the other hand, the quantum calculations required to show that this is indeed the explanation are seriously hairy, so articles aimed at non-specialists generally just present it as a given that individual photons will display this $\cos^2\alpha$ behavior.

 

[DrChinese]

Where does this formula comes from:

( cos(degrees of polarized filter difference) )²​

...
I'm asking, who came up with it, and how?

Bill answered this. Sort of.

There is actually a bit more to this formula, and it is of course the same as Malus as Bill rightly says. Nugatory alluded to the "hairy" nature of the formula. The quantum mechanical "why" for entangled photons is actually a bit complicated. The first step is seen in equation (2) of this reference:

http://arxiv.org/abs/quant-ph/0205171

Matches are the sum of 2 cases (when you have PBSs rather than filters, and use detectors set at each of the PBS output ports - 4 total):

HH + VV

But you must substitute per the reference's formula to make it work for any H and V selections. You end up with something like:

(cos(A)+sin(B)) (cos(A)+sin(B)) + (-sin(A)+cos(B)) (-sin(A)+cos(B))

Which eventually comes back to the cos^2(A-B) formula when you work it through. I probably have something mislabeled because the derivation doesn't jump out at me right now. Else there are cobwebs in my brain.

At any rate, they work it through for polarizers and so will get half the matches, so they end up with 1/2 cos^2(A-B) at their formula (10). So you can how they arrive at that.

 

[adfreeman]

It is indeed Malus's law, but the history may be confusing. Early in the 19th century, Etienne Malus observed that if you passed light through two consecutive polarizing filters at an angle $\alpha$, the fraction of light that passed the second filter would be given by $\cos^2\alpha$ and this is Malus's law. He had no explanation for this phenomenon, it was just an observed fact (and given what was known about the nature of light at the time, this is all that could be expected).

In 1861 James Maxwell discovered the equations of classical electrodynamics and that light was electromagnetic radiation obeying those equations. Malus's law can be derived from these equations, so classical physics had an explanation for what had previously been an empirically observed but unexplained phenomenon.

Quantum electrodynamics, developed during the second quarter of the 20th century, introduced the notion of photons and showed that individual photons would display the same $\cos^2\alpha$ behavior. On the one hand, this result is completely unsurprising; the easiest way of explaining how a many-photon light beam would be attenuated in this way is to assume that the individual photons behave that way. On the other hand, the quantum calculations required to show that this is indeed the explanation are seriously hairy, so articles aimed at non-specialists generally just present it as a given that individual photons will display this $\cos^2\alpha$ behavior.

Thanks for clearing that. I really don't need to see the QM calculations behind that formula; it's enough to know that it's not only derived from observation.

 

[adfreeman]

The first step is seen in equation (2) of this reference:

http://arxiv.org/abs/quant-ph/0205171

Thanks...

That paper is exactly why I don't need to see the whole calculations.

My maths are a bit rusty after just using enough to program computers along all these years. But anyway, I don't think I would understand them even if I had them fresh. For example: I only know what this "| >" is by causality -as I just saw Leonard Susskind yesterday explaining the "ket" in a lecture... better tell you all now than after you waste your time on me with formulas... It's also the reason why I was about to ask for a good book that I could use to get up to date fast and easily in all these things; I mean, I'll probably needed it if I'm going to vindicate Einstein in the next thread I'm preparing about all this.

Matches are the sum of 2 cases (when you have PBSs rather than filters, and use detectors set at each of the PBS output ports - 4 total):

HH + VV

But you must substitute per the reference's formula to make it work for any H and V selections. You end up with something like:

(cos(A)+sin(B)) (cos(A)+sin(B)) + (-sin(A)+cos(B)) (-sin(A)+cos(B))

Which eventually comes back to the cos^2(A-B) formula when you work it through. I probably have something mislabeled because the derivation doesn't jump out at me right now. Else there are cobwebs in my brain.

At any rate, they work it through for polarizers and so will get half the matches, so they end up with 1/2 cos^2(A-B) at their formula (10). So you can how they arrive at that.

This part I get.