Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Do we actually need the wavefunction?

  1. Jul 17, 2006 #1
    I am not a scientist - I am a retired software engineer. But I find the current interpretations in quantum physics rather unsatisfying. This leads me to some questions.

    My main concern is over the need for a wave function. I've recently been reading the transactional interpretation but it strikes me as needlessly complex. I have my own interpretation but would like some critical feedback from those more knowledgeable and possibly some pointers to where I am missunderstanding things : )


    It appears to me that we do not need a wavefunction or particle/wave duality to explain the double slit experiment. The observed 'wave function' of the photon could instead be a product of the experimental setup which exists regardless of whether the experiment is actually performed.


    I am taken to understand that matter and energy are flipsides of the same coin. But what if matter creates (or is created by) ripples. These ripples interfere with each other to produce a rich landscape of peaks and troughs. One could then imagine that the wavefunction is a permanent feature of the experiment itself and not some bizarre duality of, say, a photon? I'll explain...


    Let us drop stones into a pond in a pattern representative of a double-slit. arrangement As the ripples spread out and interfere we freeze the pond to capture this wave. We notice that this creates a frozen landscape of peaks and troughs. If we were to roll a marble through this landscape it would go through one slit or the other but would nonetheless behave in a manner dictated by the experiment as a whole. Now, wouldn't the frozen contours of the pond allow a marble (which observably does not pass through both slits) to have its path shaped by the stored knowledge of the slits already encoded into that rippled landscape ?

    To an observer who could see neither the ripples in the pond nor the marble in transit... wouldn't it appear as though the marble had traversed both slits and thus had some bizarre particle/wave duality ?


    Matter is energy. It is not inconcievable that all particles are surrounded by just such a standing wave. These standing waves interfere with each other such that the experiment itself produces a complex wave which dictates how introduced particles interract with the experiment. Further, these waves would appear to confer to an introduced particle some knowledge of the system as a whole and thus lead an observer to believe in a 'probability wave function' and argue about when and where the wave function collapses. Indeed, the wave function never collapsed, it is still there. And a photon is always just a particle.


    There may be some mistakes in this outlook. I admit it is not the most professional of interpretations but I believe (subject to contradiction) that it is both simple and elegant. The question is, is it at all possible and is there any existing interpretation I have missed which follows this line of thinking. The closest I have found is the transactional interpretation but, as I have said, to someone of my admittedly limited understanding it seems a little more complex than it needs to be.


    -Gary
     
  2. jcsd
  3. Jul 17, 2006 #2

    vanesch

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    The current interpretations of quantum theory are indeed unsatisfying to most, for different reasons. We are in this crazy situation where, no matter how you turn things, a rather unsatisfying view emerges, and on the other hand, where empirical success is almost complete.
    People have been breaking their heads over this issue for about 80 years now, without an entirely satisfying view coming out of the debate.
    The dissatisfaction comes about, in fact, because, on top of the formalism of quantum theory (which is, I repeat, highly successful empirically), one imposes other requirements of a more philosophical nature, and when one does so, one arrives at contradictions if one wants all of them. And relaxing one of them makes the picture ugly and unacceptable to some.

    Those philosophical requirements are:
    - the theory describes a universal ontology (meaning: elements of the theory describe "what's really out there": no solipsism), or is an approximation to such a potential underlying theory.
    - the universal ontology corresponds to our perceived concept of reality on a coarse enough level (naive realism)
    - the structure of the theory follows from some very fundamental principles from which it can be derived (elegance and simplicity / Occam)
    - the theory is universal (there's one single set of laws of nature, which govern the entire universe)

    Quantum theory runs into problems with the ensemble of the above, very reasonable, philosophical requirements. You can relax some of them, and then you can build a consistent picture. But you should think hard about what it means, to relax one of the above requirements !
     
  4. Jul 17, 2006 #3
    Thanks Vanesch,

    I guess my question is why do we choose 'particle/wave duality' over the above. I'm assuming that there must be an understood reason why the probability wavefunction cannot be intrinsic to the experimental setup - If not, occams razor would make this the preferred interpretation and we would not be debating the philosophical impact of the wavefunction and its collapse.

    Not that I am worried by the philosophical implications. I am perfectly accepting of just how abstracted my subjective reality is and so I really would never oppose any theory on that basis. I just feel that there is a simpler way of looking at this than the popularised interpretations and, unless flaws emerge, I am a strong believer that simpler is better.


    As I said, if I rolled a marble over a contoured surface its path would betray a knowledge of that surface. The marble would not have to traverse the entire surface (as a wave) in order act in a probabalistic accordance with the surface as a whole... it just needs to roll... the surface, being made of interacting waves, could provide several paths of varying likelihood incorporating interference patterns with routes the marble observably did not follow.

    It seems, at least in my limited understanding of the situation, that this could explain particle behaviour without the need for particle/wave duality, conscious observers, multiple-words or time travelling offer/confirmation waves. It just somehow feels too simple to be otherwise unless there is some fatal flaw or inconsistency. It is perhaps my inability to find the experimental basis for dismissing this simpler view which leaves me feeling dissatisfied.

    Therefore my question is: Where are the experimental inconsistencies in this view when applying it to, say, the double-slit experiment? Answering this would aid my understanding of why we adopt the particle/wave duality as the most likely explanation.

    Many thanks for your time and continued patience,


    -Gary
     
    Last edited: Jul 17, 2006
  5. Jul 17, 2006 #4

    vanesch

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    I re-read your description of the "frozen wave" and the "marble following the wave pattern" and I think you are in fact intuitively describing Bohmian mechanics, because that's exactly what it does. Have a look here:

    http://plato.stanford.edu/entries/qm-bohm/

    Note that you STILL have the wavefunction, working exactly as your "frozen wave pattern" as a *guiding field* for particles.

    Bohmian mechanics gives great insight into non-relativistic quantum theory, and has a historical importance as an example of something that couldn't exist (according to an erroneously interpreted theorem by von Neumann). It has one downside: it is not naturally compatible with relativity (you need a preferred absolute frame, and accept an ether theory).
     
  6. Jul 17, 2006 #5
    The Frenchman De Broglie had the idea :
    " If you want a small numbers of atomic orbitals, take the maxima of a wavefunktion around a circle ! "

    But did, the last 80 years, appear any better ideas ?
     
  7. Jul 18, 2006 #6
    Possibly. Thanks for the link. I'll certainly look into that - although a cursory glance at that page revealed the words 'wavefunction collapse' which, unless I'm reading it out of context, is what I was seeking to avoid.


    Sorry, you're saying that Bohmian mechanics is disproven? I hope the article tells me why otherwise I'm back where I started from... ie. Not understanding why wave/particle duality is the generaly accepted interpretation of the double slit experiment.


    I gather that quantum non-locality also has this problem. And I am fairly certain that if acceptance of an 'ether' is required for this then it should probably be required for the accepted wave/particle duality. It seems I have a long way to go in order to get to grips with this.


    I shall read the article you suggest. If you think of anything else that may help explain things to me then please do post them here.

    Again, thanks very much for your help.


    -Gary
     
  8. Jul 18, 2006 #7

    vanesch

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    No, there's no wavefunction collapse in Bohmian mechanics.

    Bohmian mechanics is not disproven, but it has serious difficulties incorporating in a natural way, relativity. It is terribly difficult - though, if I understand correctly, not impossible - to have a Bohmian version of quantum field theory. The answer of the Bohmians is of course that relativity is fundamentally wrong, and only apparent, just as in an ether theory.

    The (apparent ?) non-locality in quantum theory can be tackled in different ways, of which there are a few:

    - non-collapse views (many-worlds views) can keep locality - at the price of considering many outcomes in parallel
    - ether theories (such as Bohmian mechanics) accept non-locality as part of nature
    - it has to be said that, although there is serious experimental evidence, no explicit violation of Bell's inequalities with raw data has yet been established (for the simple reason that one needs a photodetector with >87% efficiency and neglegible dark current, something which doesn't exist). Some people claim that the "efficiency corrections" introduced this way totally bias the result and that the violation of the Bell inequalities of the so corrected results doesn't mean anything.
    - superdeterminism (also sometimes called "conspiracy") makes for the impossibility of making "arbitrary choices" which should be statistically independent of other arbitrary choices. Hence the observed correlations between non-local measurements is just a remnant of the correlations between the not-so-arbitrary choices.

    And then there are other views on QM, which say that nature deals essentially with "information" and "knowledge" and that one shouldn't seek any ontological description beyond "information". QM is then nothing else but a scheme that helps you calculate information flows between events ; events being nothing else but sources of information to be shuffled around (to other events). In such a view, "locality" and "ontology" don't mean much. I call these views "solipsist" but their advocates don't like that :smile:
     
  9. Jul 18, 2006 #8

    selfAdjoint

    User Avatar
    Staff Emeritus
    Gold Member
    Dearly Missed

    Once again, many SUACs and relationalists don't say nature is like that; they say QM is like that, a big difference. QM is the best we've had and there is currently nothing clearly better in clear view, but that could always change. What nature is like beyond what QM (and GR!) tell us we just don't know - for the time being.
     
  10. Jul 18, 2006 #9

    vanesch

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    I agree, we don't know, and I vent my personal and unfalsifiable opinion that we will never know for sure what nature is "really" like.
    But that shouldn't stop us from thinking what QM is telling us (rightly or wrongly) what it is like. Especially if we take it as a source of inspiration to go beyond it eventually.
     
  11. Jul 18, 2006 #10

    selfAdjoint

    User Avatar
    Staff Emeritus
    Gold Member
    Dearly Missed


    Well, I never say never:wink: And as for getting QM to tell us what nature is like, of course you're free to try. But note that careful is just as free to explore possibilities for getting quantum behavior out of fine scale classical nature. See the discussion on the 't Hooft birthday thread. With freedom like that, maybe all these efforts belong on a y'all come BS forum like General Philosophy or General Discussion.
     
  12. Jul 18, 2006 #11

    vanesch

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    With freedom like that, you start to see why I say that we'll never know for sure ! And the BS resides in thinking that there's some kind of "unique and universal" theory that, once we have it, will be so evident that we'd wonder how we could have missed it - without any experimental guidance.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Do we actually need the wavefunction?
Loading...