Is Quantum Mechanics an artifact of our ignorance?

[Noctisdark]

I've read a lot about QM and studied the math and how it work many and many times in several lectures in several places, but whenever I review what the theory says and compare it to how the measurement work, I come to doubt in the theory it self, I think it can even be explained using classical physics (note our measurement device are classical too), the uncertainty principle happens because when we do the measurement of position the distrub the state of the electron, (transfer the momentum because it's hitten by a photon, Campton scaterring), the infinite potential well work because a particle will bounce back and forward, measurement in different time yield in a wrong result, I think quantum mechanics work, but we are just saying stuff that happen to be true,but the theory seems like a story, it isn't the complete story, because we cannot much devices that distrubs our measurement, can some one tell me where did I go wrong?, need some serious help here :/ .

 

[DrChinese]

... the uncertainty principle happens because when we do the measurement of position the distrub the state of the electron, ... I think quantum mechanics work, but we are just saying stuff that happen to be true,but the theory seems like a story, it isn't the complete story, ... can some one tell me where did I go wrong?

Are you familiar with the EPR paradox (1935) ? They attempted to show that quantum mechanics was incomplete by attacking the Heisenberg Uncertainty Principle (HUP). https://en.wikipedia.org/wiki/EPR_paradox

However, in 1964 Bell showed that the EPR example was flawed and could not be reconciled with Quantum Mechanics. https://en.wikipedia.org/wiki/Bell's_theorem Subsequent experiments have shown the following:

No physical theory of local Hidden Variables can ever reproduce all of the predictions of Quantum Mechanics.

So basically, the idea that there is an observation limit due to "disturbing" particles cannot be correct. The HUP is the limit and there is no possibility of a more complete theory in the sense you describe. Here are some background references to assist you in understanding this conclusion (see bottom for links), which is a page I created for this: http://www.drchinese.com/David/Bell_Theorem.htm

 

[DrChinese]

In fact, ZapperZ has a great discussion of this point already on this site:

https://www.physicsforums.com/insights/misconception-of-the-heisenberg-uncertainty-principle/

 

[kith]

I am not sure if I get you right but I want to talk a bit about what it means that the "measurement device is classical".

As Heisenberg puts it: "The cut between what is considered to be part of the quantum system and what is considered to be part of the classical side can be shifted. The dividing line between the system to be observed and the measuring apparatus is immediately defined by the nature of the problem but it obviously signifies no discontinuity of the physical process. For this reason there must, within limits, exist complete freedom in choosing the position of the dividing line."

Since QM doesn't suggest a physical limit beyond which it can't be applied we should be able to use a QM description for the measurement apparatus as well. And there a problem arises because letting the apparatus interact with the system doesn't yield a single outcome but a superposition of all possible outcomes.

So your reasonable starting point, that the outcome just seems random because of the ignorance about the interaction between the apparatus and the system, doesn't seem to work.

 

[Noctisdark]

Yes, I got that, but I have a simpler question that can make things more clear, if we were a virus of just very small, can we still observe these quntum phenomena?, that virus may even obey a quantum mechanical rule, how would it feel to jump from a place to another (when a scientist does the expirement) or to pop out from the vacuum ?, or when we look at the universe from a far can we stars that seem so small obey quantum rules ?, I know this is out of topic, but just want to see the range of QM, Thanks !

 

[bhobba]

Yes, I got that, but I have a simpler question that can make things more clear, if we were a virus of just very small, can we still observe these quntum phenomena?, that virus may even obey a quantum mechanical rule, how would it feel to jump from a place to another (when a scientist does the expirement) or to pop out from the vacuum ?, or when we look at the universe from a far can we stars that seem so small obey quantum rules ?, I know this is out of topic, but just want to see the range of QM, Thanks !

Well all those things you say, while common in popularisations, or even some beginning texts, are in fact incorrect eg quantum objects do not jump from place to place. We could not have a virus small enough because it could not have the processes necessary for life.

If you want to understand QM here is a modern way to view it:
http://www.scottaaronson.com/democritus/lec9.html

These days its viewed as simply an extension of probability theory.

Thanks
Bill

 

[Nugatory]

We had another thread recently that asked the same question in a slightly different way: https://www.physicsforums.com/threa...-a-theory-of-unknowledge.826870/#post-5193519

 

[atyy]

If there is only one outcome for each measurement and no hidden variables, QM cannot be an artifact of our ignorance.

If there is only one outcome for each measurement and hidden variables, there is no known argument that QM cannot be an artifact of our ignorance. For non-relativistic QM, Bohmian Mechanics is an example of a theory in which QM arises as an artifact of our ignorance. Hidden variables that reproduce the predictions must be nonlocal or retrocausal or superdeterministic or ...

If there are multiple outcomes for each measurement and no hidden variables, the Many-Worlds approach tries to make it seem that QM is an artifact of our ignorance.

 

[DrChinese]

I was thinking of the common 3 detector experiment where the detectors results have 0.25 agreement when they are set at two different settings (AB, AC, BC) and 1.0 agreement when they are set at the same (AA, BB, CC).

I can think of a simple way to generate that result using ordinary objects. I am confident of those probabilities, although I don't think that is any solid basis to argue for or against hidden variables.

I would not mind reading further, although I have a good folder of papers, and I have the google.

I like this summary:
http://drchinese.com/David/Bell_Theorem_Easy_Math.htm

"if you randomly select any of the 3 pairs ([AB], [BC] or [AC]) enough times then you would expect to get matching results (++ or --) AT LEAST a third of the time. "

Obviously the QM results disagree. But if I had physical measurements of real objects (say mass, for example) that also gave a matching result 0.25 of the time, would that matter?

And I thoroughly agree that putting forth any idea without thorough understanding is a bad idea. I was considering whether I even should take that next step of reaching absolute certainty of the probabilities. I tend to think I'm more likely just looking at some detail that was long ago put to rest. But if the probabilities I give are correct is that just unimportant, or something that would need some further explanation?

EDIT: I apologize for not connecting your name to the link ... I really did not see your name. Your link is well written and I should have seen your name.

Thanks, hopefully the link helps. :)

Yes, measurements of different things would give different probabilities than the 25%. So mass/energy would not work. It needs to be 2 non-commuting attributes (or components thereof). For any particles: position/momentum, or orthogonal spins.

Handling the "perfect" correlation cases (a la EPR) is easy. The impossible part is finding and matching a Bell Inequality.

 

[votingmachine]

Thanks, hopefully the link helps. :)

Yes, measurements of different things would give different probabilities than the 25%. So mass/energy would not work. It needs to be 2 non-commuting attributes (or components thereof). For any particles: position/momentum, or orthogonal spins.

Handling the "perfect" correlation cases (a la EPR) is easy. The impossible part is finding and matching a Bell Inequality.

So a physical (non-quantum) answer would be something I should communicate.

I understand that is rather veiled and feel free to laugh. Almost always, later, a substantive math error is found. I'll check my numbers, but at the moment, I think the probabilities I see seem to match the Bell inequality. I readily accept that the most likely explanation is a math error. I was not concerned that my data is not a result of non-commuting attributes. Only that it matched the probabilities of the Bell inequality. I will look at it again later.

 

[Noctisdark]

Quantum mechanics in real then, it's a very disturbing and enermously un-intuitive fact, but I somewhat enjoy it, the detective who is allways guessing where the particle is following its foot prints, but there's no freaking foot-prints !, there's only an empty road (potential) and you should manage to work it out !, Thanks guys from making the concepts clear, I enjoyed reading all the articles you proposed !

 

[QST]

It seems to me that QM is very much a result of our ignorance. It poses more questions than it brings solutions. The reason we have not been able to come up with a GUT is because all the pieces of the puzzle are not yet "found". QM is only a partial understanding and thus derives its "existence" from our ignorance.

 

[ZapperZ]

It seems to me that QM is very much a result of our ignorance. It poses more questions than it brings solutions. The reason we have not been able to come up with a GUT is because all the pieces of the puzzle are not yet "found". QM is only a partial understanding and thus derives its "existence" from our ignorance.

But this is an "objection" not based on any empirical evidence, but instead, based on a matter of tastes! The fact that more and more experiments that are testing the validity of QM (check out the experiments testing "realism") are giving results consistent with QM's prediction are clear evidence that your view has no empirical basis.

Zz.

 

[Markus Hanke]

QM is only a partial understanding and thus derives its "existence" from our ignorance.

It has already been shown that "hidden variables" ( meaning our ignorance of relevant aspects ) are not able to reproduce the predictions of QM. Bells theorem shows the above to be incorrect.

 

[atyy]

It seems to me that QM is very much a result of our ignorance. It poses more questions than it brings solutions. The reason we have not been able to come up with a GUT is because all the pieces of the puzzle are not yet "found". QM is only a partial understanding and thus derives its "existence" from our ignorance.

There are two similar but different ideas about the incompleteness of our current QM theories. Both cases are similar in that we suspect an incompleteness based on theoretical grounds alone, rather than any disagreement with present experimental data.

1) The first incompleteness is related to the GUT problem you mention. Here the standard Wilsonian view is that the standard model of particle physics is incomplete. However, this "completion" may still be a quantum theory, but with different degrees of freedom.

2) The second incompleteness is related to QM itself, ie. even if we find a quantum GUT that works, is quantum theory itself incomplete? Many have suspected it to be, because of the so-called "measurement problem". This includes Einstein (whose argument for it was wrong) and Dirac, as well as the many who find many-worlds an intriguing approach. Here one should not take "incompleteness" too literally as the solution to the "measurement problem". If many-worlds does work, then quantum mechanics is complete, but each measurement we make has more than one outcome.

 

[QST]

My comment re: QM being a result of our ignorance has nothing to do with taste or opinion; it has to do with the definition of ignorance. It doesn't matter how many experiments verify QM's predictions; it is still a limited understanding. It does not give the whole picture.

 

[Jazzdude]

Today we can say with near certainty that most features of quantum theory are not an artefact of our ignorance. Those are for example the superposition principle, the uncertainty of non-commuting observables or the non-locality of entanglement.

However, other aspects that contribute to the generally perceived "weirdness" of quantum theory and that are usually collectively named the "measurement problem" may very well be related to subjective ignorance. If that is really so will likely be decided by future research. So quantum theory may become somewhat less weird, but it will never be anything like classical physics.

Cheers,

Jazz

 

[Markus Hanke]

It does not give the whole picture.

In what way exactly is it lacking ?

 

[ZapperZ]

My comment re: QM being a result of our ignorance has nothing to do with taste or opinion; it has to do with the definition of ignorance. It doesn't matter how many experiments verify QM's predictions; it is still a limited understanding. It does not give the whole picture.

But you don't know that because you are making an assumption that there is such a thing as the whole picture and that we don't have access to it. You've made an a priori assumption, and I'm showing you that there is no physical evidence that your assumption is correct. You certainly haven't offered any evidence that it is.

Zz.

 

[ZapperZ]

Today we can say with near certainty that most features of quantum theory are not an artefact of our ignorance. Those are for example the superposition principle, the uncertainty of non-commuting observables or the non-locality of entanglement.

However, other aspects that contribute to the generally perceived "weirdness" of quantum theory and that are usually collectively named the "measurement problem" may very well be related to subjective ignorance. If that is really so will likely be decided by future research. So quantum theory may become somewhat less weird, but it will never be anything like classical physics.

Cheers,

Jazz

I agree. Unfortunately, some people used the term "weird" as if it is a valid evidence against something such as QM without realizing that it is a description based on a matter of tastes. There are many things that some people find weird but others find to be common. This is precisely the description based on a matter of tastes. QST doesn't seem to be aware of this.

Zz.

 

[atyy]

But you don't know that because you are making an assumption that there is such a thing as the whole picture and that we don't have access to it. You've made an a priori assumption, and I'm showing you that there is no physical evidence that your assumption is correct. You certainly haven't offered any evidence that it is.

There is no physical evidence that our theory of quantum gravity is incomplete either. Yet on theoretical grounds it is suspected to be incomplete.

 

[bhobba]

My comment re: QM being a result of our ignorance has nothing to do with taste or opinion; it has to do with the definition of ignorance. It doesn't matter how many experiments verify QM's predictions; it is still a limited understanding. It does not give the whole picture.

May I suggest you have a look at the following:
http://arxiv.org/pdf/quant-ph/0101012.pdf

We understand the why of the formalism - it's required for continuous transformations between so called pure states because classical probability theory lacks this key requirement to model physical systems. Basically if you have a system that goes from one state to another in a second it should go through some state in half a second.

What it means however is another matter - eg do we have have an observation created reality or is it pre-existing which is tied up with the so called measurement problem Jazz mentioned. But meaning and ignorance are two different things. That problem is likely to be solved by future research - hopefully anyway.

I know it seems like semantics, and I am usually rather anti semantics as it to my mind it doesn't illuminate anything - but this one I think is important.

Thanks
Bill

 

[atyy]

I knoll it seems like semantics, and I am usually rather anti semantics as it to my mind doesn't illuminate anything - but this one I think is important.

Another funny thing about terminology is that actually the measurement problem is the that quantum mechanics without hidden variables is not an artifact of our ignorance:) This is because pure quantum mechanics only gives decoherence and a density matrix that is not ignorance-interpretable.

So proposals like Bohmian Mechanics try to make it such that when hidden variables are included, quantum mechanics is an artifact of our ignorance.

 

[votingmachine]

I've read a lot about QM and studied the math and how it work many and many times in several lectures in several places, but whenever I review what the theory says and compare it to how the measurement work, I come to doubt in the theory it self, I think it can even be explained using classical physics (note our measurement device are classical too), the uncertainty principle happens because when we do the measurement of position the distrub the state of the electron, (transfer the momentum because it's hitten by a photon, Campton scaterring), the infinite potential well work because a particle will bounce back and forward, measurement in different time yield in a wrong result, I think quantum mechanics work, but we are just saying stuff that happen to be true,but the theory seems like a story, it isn't the complete story, because we cannot much devices that distrubs our measurement, can some one tell me where did I go wrong?, need some serious help here :/ .

That is precisely what Einstein argued repeatedly, with the most famous publication titled: "Can Quantum-Mechanical Description of Physical Reality Be Considered Complete?". His position was that it was an incomplete description, that there is a fundamental reality, particles have position and momentum for example, and that with sufficient cleverness we can find both. Einstein's proposed cleverness was to make two identical particles and measure position of one (and thus know the other), and then momentum of the other.

The unfortunate thing is that exact uncertainty measurement cannot be done. But other experiments that generate exact pairs of things ("entangled" things) have shown that if you measure property "A" you actually do lose information about property "B" of the other entangled particle. Essentially it is as if you had that perfectly matched pair of particles and upon measuring the momentum of one exactly, the other particle knew it, and became unmeasurable in location. The experiments show that to be true even when the particles are separated at a distance that "knowledge" must exceed the speed of light.

The proposal by Einstein (and Podolsky and Rosen) was a very clever way to get at defeating the limits of measurement uncertainty, and to measuring "completely", the underlying reality. I am impressed with the idea.

The EPR (I call them that, they may have better names ... Bell comes to mind) experimental results are impossible. Except for the part where they are possible. You are not alone in dismissing the results and saying this will all be explained better someday. I've heard many people say a similar thing. I think a complete and exact description of small scale things will always be impossible. Or another way of saying that ... the complete description is a bit less filling than expected.

It is unfortunate that I was introduced to the uncertainty principle as a measurement problem. Then the trick is to figure out a sufficiently clever way to acquire knowledge, and defeat ignorance. And acquire a complete understanding. As you say, it looks like what we have "isn't the complete story". That becomes an endless philosophical/speculative loop though, when you take that as an assumption.