No paradox in the EPR paradox

[Sherlock]

We've been around on this so many times here, I'm already dizzy. So I'll make a few comments, and then give you the last word. Then we can let other people assess the two views and decide for themselves.

Each of the two views depends on an, imo, unfounded interpretation of the meaning of quantum theory. The relationship between the theoretical unitary evolution and the evolution of quantum systems in real, 3D space is just not known.

What I believe is that quantum theory provides one way (so far, apparently, the best way) of calculating the average results of large numbers of identically prepared experiments on quantum systems. Beyond that, any meaning that I attach to the formalism is, for the moment at least, purely speculative.

The Bell locality condition isn't necessarily an evaluator of locality vs. nonlocality. Disagreement with this condition does indicate that the statistics of spatially separated detectors are not independent, that they are related. But this doesn't necessarily mean causal dependence due to some sort of superluminal transfer between the filters or detectors during measurement intervals. There is, imo, a better way to approach understanding how the correlations can occur in a universe where all propagations are limited by the speed of light.

Nevertheless, nonlocality in nature remains an interesting possibility. But, I don't think that the same can be said for MWI.

If it weren't for the claim that MWI saved locality, I submit that *nobody* would take MWI even remotely seriously. It's just too stupid/crazy/la-la-land to even consider *science* unless there's some very powerful argument in its favor. I concede that saving locality is in the ballpark of such an answer. But I still come down on the side of saying: the price is *way* too high.

Locality doesn't really need to be saved, because the inference of non-locality depends on an interpretation. If there was actually any physical evidence of non-locality, then there wouldn't be any talk about saving locality. There would be a joyous reworking of physics to incorporate this wonderful new phenomenon that would be embraced by all physicists.

iiuc, the relative-state interpretation was forwarded by Everett to deal with what some see as an inconsistency between the theoretical evolution of the wavefunctions representing the possible results of an individual measurement, and the directly observed fact that only one of these possibilities is actually produced per individual measurement.
Why that's a problem, I don't know.

To make reality fit their interpretation of the meaning and application of quantum theory, the MWIers invent as many worlds (branches of reality) as needed to accommodate the possible results of measurements. This is, to me, obviously a perversion of the meaning and application of quantum theory, and goes against the basic tenet of empirical science.

So, I agree with you, ttn, wrt your assessment of and objections to MWI. But, I disagree with your interpretation of the meaning of quantum theory insofar as you hold that it implies non-locality in nature. I'm somewhat surprised that vanesch has adopted the MWI approach. And, I'm sorry to disagree with either of you on anything, because you have been very good teachers, but wrt this matter I must ... until otherwise corrected.

To summarize, there is no definitive interpretation of the physical meaning of quantum theory beyond its obvious role as a method of calculating experimental results. There is no locality problem. There is no wavefunction collapse problem. There is of course a real measurement problem, but it has to do with what can be experimentally determined rather than some pseudo-difficulty arising from unnecessary interpretations of the formalism.

 

[LnGrrrR]

I came over from another thread, so forgive me if I'm 'jumping in' so to speak. Just a quick question...

A thought experiment...Qm is said not to violate light speed because no message can be transferred faster than light speed, correct?

Let's take the classic, "Jane is at position A and Bob is at position B." We'll separate them by, oh, a lightyear. Now place Mike at position C, right in between those two.

We find a way to sync up both Jane and Bob's speed so they are both going the same speed and have the same clock timing. At a predetermined time, Bob looks at his entangled pair's spin at the same time that Jane looks at her entangled pair's spin. They both then transmit the measurement to the middle station.

Wouldn't this be a way around the 'communications can't move faster than light' problem? C could determine if the pairs still showed the same entanglement measures we get normally, but do it faster than the entangled pair could transmit the information (being in the middle between those two).

 

[DaveC426913]

Wouldn't this be a way around the 'communications can't move faster than light' problem? C could determine if the pairs still showed the same entanglement measures we get normally, but do it faster than the entangled pair could transmit the information (being in the middle between those two).

I may be missing a key element.

How does this transmit a message ftl? Where does the message start and end that it has traveled > c? Neither A nor B know what happened at C until C communicates it to them at <= ftl.

 

[LnGrrrR]

DaveC,

The message itself wouldn't be transmitted faster than light...but if the experiment could be done repeatedly, and the photon that was 'collapsing' at Jane's end collapsed at Bob's end also, then that could show that one photon was affecting the other faster than the speed of light.

Jane --------------Mike------------Bob

If Jane and Bob send their messages at the speed of light (Jane sending the 'collapsed the waveform' message and Bob sending confirmation of said collapse or not), Mike will receive them in half a light year. However, the 'message to collapse' from Jane's entangled photon couldn't possibly reach Bob's other photon before it reached Mike, thereby nullifying locality. However, if Bob's photon, for some reason, didn't 'collapse' immediately, then locality would be preserved.


(Did that explain it better? Or is there something vital I'm missing?)

 

[RandallB]

(Jane sending the 'collapsed the waveform' message
and Bob sending confirmation of said collapse or not)

(Or is there something vital I'm missing?)

LnGrrrR
I’m sure you don’t realize it and may have a hard time understanding this – but your just making this up as you go.

Huge vital parts missing:
*Jane cannot tell if she is collapsing a wave function – she can only make an observation.
*Bob cannot see a wave function collapse – he can only make an observation.
Messages between Bob & Jane are just that, simple messages, about observations that can be collected over many years to review statistically to decide about correlations etc. (Much EZ’er in a smaller lab).
Mike seeing only normal messages can’t help at all on “local” or “locality”.

To understand better, I’d recommend your using this forum to get up to speed on the key experiment, QM Entanglement via ERP Bell.
Use the advance search function to start search for threads with user ‘DrChinese’ & Key words including ‘EPR’, ‘Bell’, ‘Entanglement’ limit it to titles only --- you will get tons of good starting places.

Not that DrC is the authoritative reference for EPR-Bell on this forum – he just is for me. Plenty of other Advisors and Mentors helping out in those same threads.

EPR-Bell is the only experiment that can be considered as proof that QM is the correct solution. Now being considered so, doesn’t say that everyone agrees that is so – you will find plenty contrary opinions explaining why QM has not yet been proven complete in the same threads. Who’s right? – well you could ask me, but you’ll only get my opinion, review the explanations to understand “the explanations” and why they believe in them. Then worry about forming your own opinions.

Any explanation, wave collapse, MWI, superposition, guide wave, etc. etc. must understand and address the EPR-Bell issue. You will learn a lot just from reviewing the existing information and links in this forum. But don’t worry, you will still have questions after those threads – better ones - and the guys will still be here to address them.
Take your time to read and think, you have a lot to cover.

RB

 

[LnGrrrR]

RandallB,

Yes, I've certainly had problems with that Bell's inequality. I think there's too many negatives in the whole "non violations of an inequality" or whatever it is ;)

I will take the time to review those, but in the meantime, I thought that a question plaguing (for lack of a better term) QM was the question of whether or not locality can be/is violated.

Mayhaps I'm misunderstanding it, but if an entangled pair gets sent off to Jane, and to Bob, and Jane makes a measurement on said entangled pair (say, for instance, hers is spin up), and Bobs is always the opposite (spin down) and they send the information...wouldn't that work to solve the locality issue?

Measuring the photon would 'collapse' the waveform, correct? Or am I conflating the wave/particle duality issue with entanglement?

Maybe what I should be thinking up is a light spanning sort of 'double slit' experiment...not sure.

(I'd also like to note that I don't think I'm coming up with some revolutionary thought that hasn't been explored before...I'm sure my ideas have. I'm just wondering what the answers to these assuredly already asked questions are. :)

 

[RandallB]

I don't think I'm coming up with some revolutionary thought that hasn't been explored before...I'm sure my ideas have. I'm just wondering what the answers to these assuredly already asked questions are.

I understand what your going though better than you might guess - problem is there is no simple answer that you are going to understand.

At least remember when YOU make a measurement, how do YOU tell who you are. Are you a Jane and collapsing the waveform, or are you a Bob and seeing a waveform that has already been collapsed (Even if it was collapsed by a Jane in some future time! there's a headache).
You can only make the observation, without seeing the common link between the two (at least so far). Only after the fact data comparisons are giving you WIERD results that indicate the WIERD theories that Einstein complained about.

Start by understanding the arguments already provided as best you can, you may never be able to pick just one as "correct".

 

[vanesch]

Measuring the photon would 'collapse' the waveform, correct? Or am I conflating the wave/particle duality issue with entanglement?

Not necessarily. Wavefunction collapse is a formal idea which is NOT directly observable. As has been pointed out previously, the only thing that is observable, are, well, observations.

There are several views to look upon "wavefunction collapse" - they are in fact the different interpretation schemes of quantum theory. I myself am a proponent of the MWI view (to put my cards on the table), but I recon that this is just *A* view amongst many. Nevertheless, it illustrates that "collapse" is not something that is to be taken for granted in a naive way (kind of "plooof" thing happening).

There is first of all the Copenhagen view (which is usually adhered to by most introductory textbooks on quantum theory because it allows you to get started with the formal calculations easily). The Copenhagen view is in fact a rather strange view on nature: it says that REALITY out there consists of classical reality for macroscopic objects (there's no quantum theory description of macroscopic objects), and a NON-DESCRIBABLE reality of microscopic objects. Nevertheless, there is a way to calculate THE INFLUENCE OF THE MICROSCOPIC WORLD ON THE MACROSCOPIC WORLD, and that is by using the formalism of quantum theory - but it is only that: the formalism is a way of calculating the influence of the microscopic world on the macroworld (which is, I repeat, purely classical). But that formalism is NOT saying what's going on, really, on microlevel.
The link between the undescribable microworld and the classical macroworld is by a process called "measurement" (which is left open to the intuition of the user). This measurement takes on two forms: one is "preparation" (when the quantum system is prepared by the macroworld: as such, we know what is the initial wavefunction to be used) and the other is the proper measurement, which gives us probabilities of outcomes.
In the Copenhagen view, there is nothing physically happening during "collapse" because the wavefunction doesn't correspond to a physical object, but is just a formal way of calculating what the microworld is doing on the macroworld - and claims that the microworld is undescribable as "an underlying reality".

In the closely related von Neumann view, microscopic systems are described by a wavefunction (which takes on some more ontological reality here), but *somewhere* along the chain between the microsystem and the conscious awareness of the outcome of measurement, a *physical collapse* occurs.

In the information point of view, all physical theories are just formal tools to organize our knowledge of outcomes of measurement, and are not supposed to be a description of what physically happens between those measurements. As such, collapse is like the collapse of a probability function: when you learn about the outcome, suddenly your probabilities are changed because of that new information. But probability functions are not physical objects, but just descriptions of our knowledge. There are variations on this view: some say that, of course, there MUST be a physical underlying reality, but QM isn't describing it ; and there are others who say that talk about an underlying physical reality is serving no purpose, and all we need is an organizing principle of our knowledge and observations.

And finally, in the MWI point of view, the wavefunction IS the physical description of the micro- and macroworld, and collapse is just an apparent phenomenon related to subjective observation and not something that happens to the physically real wavefunction. This then leads automatically to the continued existence of the parts of the wavefunction which would otherwise be projected out, and these are the "parallel worlds" of the observer: it is postulated that the subjective experience of the observer is only aware of one of them.

But all these views are speculations on how to look upon the formal elements in quantum theory, and in only two views the wavefunction is taken as something physical: in a von Neumann view (but there, it is not clear WHEN and WHERE collapse occurs) and MWI. In all other views, the wavefunction is just a formal tool, and one does NOT try to say what's going on physically. So no theory explicitly says when a collapse occurs *physically* and how it "propagates stuff through space" or something.

 

[LnGrrrR]

Vanesch,

First, thanks very much for a clear and concise explanation of the terms. The most 'sensible' would seem to be a hidden variables theory, but none of these stand up to explanation. So, as a swimmer who must adjust to the temperature of the water, I'm slowly trying to rearrange my ideas about what reality SHOULD be, and reform them into what reality IS (or at the least, get a better/more correct view of it).

Some comments on the differing theories...

Copenhagen/Von Neumann - There's something both very satisfying and UNsatisfying about stating that the world is, at it's smallest levels, random. It does seem to provide a sense of 'awe' in some cases, but I'm not sure (philosophically mind you) what that says about 'scaled-up' reality. How much would a 'random world' on a quantum scale affect macroscopic objects?

Information - An interesting POV...IIRC, I read an analogy of this on another site. It said something about where you heard that there was a car wreck near your house, and you worried that it might be a loved one. You were in a 'superposition' of sorts, of hoping your loved one was alive but worrying she might be dead, and once you discovered the outcome, it 'collapsed' your superposition of states. I think I might be inclined to lean towards this one, but I'd have to read more. (Also, I disagree with saying that we don't need to worry about this, just as I disagree with philosophers on the mind-body problem saying that it's not an issue.)

MWI - This theory, upon further reading, does seem to 'fit' with the data provided so far. However, it's certainly not very intuitive, and it seems that it is widely accepted due to a LACK of data for other views, rather than a positive proof for its own (as the different universes can not interact, it would be tough to measure them. :)

Anyways, thanks for the headsup Vanesch. Very informative. :)

 

[vanesch]

Vanesch,

First, thanks very much for a clear and concise explanation of the terms. The most 'sensible' would seem to be a hidden variables theory, but none of these stand up to explanation.

Eh, yes, I didn't discuss it, because it is all together a DIFFERENT theory, and not an interpretational scheme of the quantum formalism. However, there is of course Bohmian mechanics, which is empirically equivalent to quantum theory (although it has some problems with quantum field theory).

In Bohmian mechanics, the "ontology" of the world is two-fold: there are on one hand particles with positions and momenta like in Newtonian physics, and there is on the other hand the (non-collapsed) wavefunction (as in MWI). The wavefunction "guides" the particles (is responsible for the forces). However, there's something a bit strange: this only gives rise to the probabilities of quantum theory if we take it that there is an initial uncertainty on the particle positions which corresponds exactly to the probability distribution dictated by the wavefunction. This condition is called the "quantum equilibrium condition". If you do NOT take this as initial condition, then Bohmian mechanics is NOT empirically equivalent to quantum theory.

Nevertheless, apart from this problem of initial knowledge, it has to be said that Bohmian mechanics does present a rather clear ontological picture of what happens at microscale.

The reason I don't adhere to it is that Bohmian mechanics violates special relativity in its formalism (it is not Lorentz invariant). The guiding of the particles by the wavefunction is non-local (immediate action at a distance) - which makes this formulation incompatible with special relativity ; in fact, to write down Bohmian mechanics, one needs to work in a preferred reference frame.

 

[LnGrrrR]

Is it Bohmian mechanics that assumes that all particles in the world are 'interconnected', hence the spooky action at a distance being instantaneous?

 

[vanesch]

Is it Bohmian mechanics that assumes that all particles in the world are 'interconnected', hence the spooky action at a distance being instantaneous?

Yes. In THIS theory, there is a serious violation (in principle) of special relativity. But that's no surprise, because its formulation is already non-lorentz invariant.
However, the magic that occurs is that IF you accept the quantum equilibrium condition (= a specific uncertainty on the initial conditions) then this works out in such a way that you cannot use this spooky action at at distance to send messages faster than light (although the physical mechanism IS present in Bohmian mechanics, which is the quantum potential). If you do not accept this initial uncertainty, then you CAN send messages faster than light in Bohmian mechanics ; however, then, its predictions do not agree with those of quantum theory.

 

[LnGrrrR]

If I've read right, Bohmian mechanics that don't accept the QEC don't seem to have very good experimental arguments, correct? Or have I misunderstood?

 

[vanesch]

If I've read right, Bohmian mechanics that don't accept the QEC don't seem to have very good experimental arguments, correct? Or have I misunderstood?

Bohmian mechanics is never actually considered without the quantum equilibrium condition. You can read a rather good summary on it on
http://en.wikipedia.org/wiki/Bohmian_mechanics ;

A better, more profound article can be read here:
http://plato.stanford.edu/entries/qm-bohm/

There, point 9 addresses the issue of quantum equilibrium.

I like the following statement, found towards the end:

I know that most men, including those at ease with problems of the highest complexity, can seldom accept even the simplest and most obvious truth if it be such as would oblige them to admit the falsity of conclusions which they have delighted in explaining to colleagues, which they have proudly taught to others, and which they have woven, thread by thread, into the fabric of their lives.

 

[reilly]

Not necessarily. Wavefunction collapse is a formal idea which is NOT directly observable. As has been pointed out previously, the only thing that is observable, are, well, observations.

There are several views to look upon "wavefunction collapse" - they are in fact the different interpretation schemes of quantum theory. I myself am a proponent of the MWI view (to put my cards on the table), but I recon that this is just *A* view amongst many. Nevertheless, it illustrates that "collapse" is not something that is to be taken for granted in a naive way (kind of "plooof" thing happening).

....
In the information point of view, all physical theories are just formal tools to organize our knowledge of outcomes of measurement, and are not supposed to be a description of what physically happens between those measurements. As such, collapse is like the collapse of a probability function: when you learn about the outcome, suddenly your probabilities are changed because of that new information. But probability functions are not physical objects, but just descriptions of our knowledge. There are variations on this view: some say that, of course, there MUST be a physical underlying reality, but QM isn't describing it ; and there are others who say that talk about an underlying physical reality is serving no purpose, and all we need is an organizing principle of our knowledge and observations.But all these views are speculations on how to look upon the formal elements in quantum theory, and in only two views the wavefunction is taken as something physical: in a von Neumann view (but there, it is not clear WHEN and WHERE collapse occurs) and MWI. In all other views, the wavefunction is just a formal tool, and one does NOT try to say what's going on physically. So no theory explicitly says when a collapse occurs *physically* and how it "propagates stuff through space" or something.

Excellent post; very clear indeed. But, the infamous but, I disgree with certain notions you present.

First, nobody in their right mind can take Copenhagen/vonNeuman seriously -- that approach was developed by supremely brilliant men at a time when virtually everybody was naive about human cognition, and, I think, about the underpinnings of practical probability theory as well. This tied into very strong connections with 19th century notions of reality, reason, and the ultimate hybris of turn-of-the-century physicists, that they were in shouting distance of understanding it all. The plain fact is nobody really has a clue about the basics of quantum measurements -- why only one result at a time? Is this fundamental to nature, or is it a constraint created by our perceptual mechanisms? Look how we argue about, is the moon there when no one is looking? Is there life between measurements? Entanglement. Decoherence.

We know how to measure, how to make sense of the results (well, sometimes), but, how in the world does this superposition end up unsuperimposed? (Unfortunately termed wave function collapse. Unfortunate, because once said there was then no choice but to try to explain the unexplainable -- how to get physical certainty in a probabilistic world? And, in my opinion, they badly bungled the job. Many wonderful 19th century notions are simply inapplicable to 20th century and current physics, c.f. causality, continuity, certainty, ... .(Earlier folks were smart enough to avoid the collapse issue.)

These days, in practice, Copenhagen means Born and the probability interpretation, all of which, in my view, saved the day from the tortured dances of the founders. One number wins the lottery -- could be a degenerate state --, one counter clicks in a scattering experiment. We certainly never worry about any sort of a collapse in the lottery, or in finding or not finding lot's of traffic on our way home from work. In fact we deal with these uncertainties and probabilities -- subjective or objective --much like the current phrase, "Get over it", it's just the way the world works, With Born, we do the same thing; apply basic probability and statistics to quantum phenomena.

Forget a physical wave function,. forget collapse. To me, the simple fact is that the idea of collapse of a physical wave function is nothing but a black hole of problems, so why bother? (I suppose you could term the electrons in an electron microscope as a physical manifestation of a wave function. Just like the lottery -- provided one can release one's self from the dominance of 19th century ideas, at least in physics.

Understanding? Reality? Always changing. While I know that even the great Feynman noted that, in essence, nobody really understood quantum theory, I take the opposite view. Again, much of my notion is that we must understand QM on its own terms, rather than with old, possibly conflicting ideas. When in Rome ... There are many texts and articles that use physical arguments for QM issues --what is that but a direct sign of understanding? (Semiconductors, lasers, Fermi-Thomas techniques, and on-and-on.)

What is language but a formal tool?

And, what exactly does it mean to "say what is going on physically?"

Does anybody think that experiments could detect whether a wave function has a physical manifestation, whether collapse occurs, or detect evidence that MWI has any basis in fact?

Regards,
Reilly

 

[vanesch]

And, what exactly does it mean to "say what is going on physically?"

Isn't the answer to this question exactly what is the core mental activity when doing "physics" ? Isn't the construction of a mental picture (in my case, an identification between mathematical objects and physical objects) of what "goes on physically" the essence of develloping an intuition for physics ?

In the same way a biologist thinks of cells and biomolecules as the mental pictures that help him construct his thinking about his subject matter or a pharmacologist helps him think of strategies to fight a certain illness ?

I'm sorry, but to me, it is helpful to think, in the case of a double-slit experiment for instance, that an electron went through both slits at the same time and then interfered with itself. I like to keep that mental picture, and it helps in figuring out what are the essential contributions, and what are secondary effects. On the other hand, I have difficulties doing that when I am not entitled to "my mental picture of reality" and when I'm supposed to be thinking about "formal tools to predict statistical outcomes of ensembles of experiments". There's no intuition to be gained from that, is there ?
As I said elsewhere, isn't such a mental picture the WHOLE PURPOSE of the concept of "reality" ? So the "difficulty" with quantum theory is to find such a picture, which should be suggestive of the entire formalism in a natural way.

 

[reilly]

vanesch --We agree on this. My notion was that you were talking about a more formal, precise idea of physical reality or 'what's going on".

In regard to personal styles of reasoning, there's a fantastic book by Jaques Hadamard, The Psychology of Mathematical Invention (Dover). Hadamard interviewed many world class mathematicians as well as Einstein on their patterns of work and thought, and tied things together stimulated by an experience of Poincare -- who worked for months on a problem in Fuchsian functions and made little progress, so he stopped. Several months later, the solution came to him as he was stepping onto a bus. Poincare asked, Why, How...The great mathematician latched onto Freud's idea of the unconscious, and postulated that his unconcsious mind continued to work on the problem even though he had consciously stopped. Hadamard built on Poincare's experience and ideas, and demonstrated that it makes sense to talk about unconscious reasoning and work -- based on his interviews and conversations.

So, why deal with Hadamard? Well, Hadamard also develops the idea of differing views of reality within the creative side of math and physics -- Einstein's trip riding on a light wave is not exactly characteristic of hard-nosed reality. The boundaries between illusion, imagination, and reality can get quite fuzzy -- those who tend to think in images can have a very difficult time translating their thought into spoken or written language, perhaps characteristic of silent or reclusive geniuses. Hadamard gives, I think, a compelling case for the highly subjective nature of internal views of reality, that is, for differing mental pictures.

For example, I think of the double slit experiment with photons, electrons or whatever, in terms of water waves -- I can see what's going on. I prefer to avoid the cognitive dissonance I encounter when thinking about particles in a double slit experiment. We clearly have very different mental pictures, and thus see different realities.

Yes, the whole point of physics is to gain understanding -- by any means possible. Because the mathematics of much of physics is highly difficult, we are forced to operate by intuition a great deal of the time. The "pictures" we have built based largely on classical physics are several hundred years old -- or, at least a whole bunch. These pictures are very much at odds with the "pictures" commonly accepted prior to the Enlightenment.

So the prime mover folks had to be screaming over Newton's ideas; over the heretical idea of a solar centered universe. But, as is pointed out in great detail in Daniel Boorstien's, "The Discoverers", and also in "Longitude" by Dava Sobel, and in countless histories; the shift in viewpoint came from mainly pragmatic impetus. The scientific view of the world made no sense at all to many, not all of them stupid by any means. And, there are still such people around -- they have not caught up with the paradigm ( I use this word about once a decade, it being vastly overused. But I rely on T. Kuhn as my reference here.) shift of roughly four centuries ago.

Many of us have worked out our own approach to building intuition, quantum or otherwise. The fact that notions of a quantum reality do not fit nicely into a 19th century view of an invariant, objective universe simply means, given historical precedents, that the criticisms and discomfort of and with QM will die a natural death.

You say:So the "difficulty" with quantum theory is to find such a picture, which should be suggestive of the entire formalism in a natural way.

What does "suggestive of the entire formalism in a natural way" mean? Who gets to define "natural?" (The way I think about QM is natural to me, and clearly not natural to you.) You talk about the importance of your way to your work, and illustrate an example re slits. You are, I am, and everybody else is, of course entitled to our mental practices, So why require a monolithic picture of QM? I've read and listened to many physicists talking about QM topics in a highly intuitive fashion -- I completely reject the idea that physicists do not understand QM -- the only way to counter my contention is to attempt this understanding with 19th century notions, and such an attempt is, as we all know, fraught with problems.

You state:
I'm supposed to be thinking about "formal tools to predict statistical outcomes of ensembles of experiments". There's no intuition to be gained from that.

Who in the world suggests that you are supposed to be thinking in such terms? What a meaningless statement, a "straw man". And, if you do, better take an applied QM course to get back to daily physics reality. In my experience, I've never heard of such a thing -- but then I was trained to believe the height of physics was to explain a complex phenomena with no math.

Regards, Reilly

 

[LnGrrrR]

Thanks for the great links DrC. I'm busy reading up on Bell's Inequality now, and it certainly is helping me understand bit by bit.

 

[vanesch]

vanesch --We agree on this. My notion was that you were talking about a more formal, precise idea of physical reality or 'what's going on". [...]

Great post :-)

 

[koantum]

but to me, it is helpful to think, in the case of a double-slit experiment for instance, that an electron went through both slits at the same time and then interfered with itself. I like to keep that mental picture, and it helps in figuring out what are the essential contributions, and what are secondary effects. On the other hand, I have difficulties doing that when I am not entitled to "my mental picture of reality" and when I'm supposed to be thinking about "formal tools to predict statistical outcomes of ensembles of experiments". There's no intuition to be gained from that, is there ? As I said elsewhere, isn't such a mental picture the WHOLE PURPOSE of the concept of "reality" ? So the "difficulty" with quantum theory is to find such a picture, which should be suggestive of the entire formalism in a natural way.

Congratulations if you can think that way. I, for one, cannot conceive of an electron as being in two objectively distinct places at the same time. "Electron here" and "electron there" implies the existence of two electrons unless there is no objective difference between "here" and "there". What I can conceive is that under certain conditions (which I need to elaborate on at this point) the distinction we make between "here" and "there" is a distinction that Nature doesn’t make. It exists solely in our heads. I have discussed this in considerable detail http://thisquantumworld.com/twoslits.htm" .
I also cannot attach any meaning to the statement that the electron interfered with itself. This is just the kind of naïve reification of mathematical expressions which makes it impossible to arrive at a sensible conception of reality. Such reifications may have heuristic value as visual aids but they may just as well be seriously misleading. If you want to disentangle the ontological message of quantum mechanics from its mathematical structure, then it won't do to think of one and the same complex number as (i) the amplitude associated with the alternative "electron goes from A to B" and (ii) a representation of the electron actually going from A to B.
I of course agree with you that we should be looking for an ontology that is suggestive of the entire formalism in a natural way. But your kind of ontology won't take you there. (Where I disagree is when you demand from it more than being simply suggestive, as you seem to have done in a different thread.)