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

Ranking of Quantum Mechanics interpretations?

  1. Sep 20, 2005 #1
    Is there somewhere something like a ranking of the different interpretations of Quantum Theory, from the most widely embraced by physicists to the least?
    Something like physicists voting in a poll ...
  2. jcsd
  3. Sep 21, 2005 #2
    I gather that the decoherence (Zeh) approach is popular, as is Many Worlds.
    However, shut-up-and-calculate is ahead by miles.
  4. Sep 23, 2005 #3
    Is decoherence an interpretation? I thought it was a mathematical description of how the wave function collapses or something, although I confess to not knowing.
  5. Sep 23, 2005 #4


    User Avatar
    Staff Emeritus
    Gold Member
    Dearly Missed

    There is a mathematical and physical demonstration that the wave function of a system interacting with the big environment "diagonalizes" very quickly - all the mixed states evolve toward pure states. This is decoherence, and as a tendency it is a fact of nature. The attempt to use this fact to avoid quantum weirdness is an interpretation.
  6. Sep 23, 2005 #5


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    There's a brief mention of it at Wikipedia http://en.wikipedia.org/wiki/Many_worlds

    The Max Tegmark results are given here:
    http://arxiv.org/PS_cache/quant-ph/pdf/9709/9709032.pdf [Broken]
    Last edited by a moderator: May 2, 2017
  7. Oct 4, 2005 #6
    For all intent and purposes, is the MWI our best GUESS at what's going on, since from what I understand Copenhagen is the "stick to the math", "don't worry about philosohpy" interpretation (if it is an interpretation)?
  8. Oct 8, 2005 #7
    except that shut-up-and-calculate is not an interpretation, it is instead a refusal to interpret.

    Thank goodness that scientific truth is not decided by democratic elections!

  9. Oct 8, 2005 #8
    The Copenhage "interpretation" also refuses to say anything about the
    reality or nature of unobserved SVs/WFs.
  10. Oct 8, 2005 #9
    can someone summarise just what needs to be interpreted?

  11. Oct 8, 2005 #10


    User Avatar
    Staff Emeritus
    Gold Member
    Dearly Missed

    In the quantum mechanics math, which works so well and makes such accurate predictions, the "reality" of, say, an electron is represented as a vector in an infinite dimensional abstract space, or you could think of it as a wave, but whichever way you look at it, it's not a feature of our world. When we make observations, that's represented in the math as and operator - like an infinite dimensional matrix - acting on the vector, or the wave, and it produces a set of real numbers. These numbers are interpreted as the probability of seeing the electron at various points, or with various different momenta.

    So this mathematics doesn't tell us anything about the behavior of the electron in this world, it is just about our observations and the probabilities of what we will see. The interpretations of quantum mechanics are intended to provide some idea of what the math means.
  12. Oct 8, 2005 #11
    In other words, our concepts of "wave" and "particle" do not apply to quantum objects. There is no simple analogy from the macroscopic world which helps us to visualise a quantum object.

    Thank you. It seems to me then, on this basis, that neither "shut up and calculate" nor the Copenhagen "interpretation" are true interpretations (neither gve us any idea of what the math means)? An interpretation should purport to give us some insight into ontology, into what is really going on - neither "shut up and calculate" nor "Copenhagen" claims to do this.

    MW is an interpretation. Decoherence is an interpretation. Bohmian mechanics is an interpretation. Feynman-Wheeler/Transactional theories are also interpretations.

  13. Oct 11, 2005 #12
    In my personal studies, the greatest revelations of all have come from considering these interpretations. eg. That the universe may be capable of pure randomness or operate in ways that will remain impenetrable to experiment forever. I find these very satisfying insights into ontology. I'd sooner concede this, than believe in unthinkable numbers of different universes I can never get to, or accept that we are surrounded by advanced waves travelling the wrong way through time (although I like to flirt with these ideas to, from time to time :smile: ).
    Last edited: Oct 11, 2005
  14. Oct 11, 2005 #13
    How can one achieve a "revelation" from something that remains "impenetrable to experiment forever"? Grateful for your insights here.

    If the universe is "impenetrable to experiment forever", there is not much point in discussing it further, is there?

    Can you explain results of entanglement experiments, or the results of the delayed choice experiment, in any other way?


  15. Oct 11, 2005 #14
    The impenetrability is a revelation to me.

    No, it would involve maths that are long since beyond me anyway.
  16. Oct 11, 2005 #15


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Zeilinger did a pretty decent job of this in a paper he published in 1999:
    http://www.quantum.univie.ac.at/zeilinger/foundations.pdf [Broken]
    The above describes "foundational principals" which provide a conceptual framework for relativity. He points these out as an example of 'foundational principals'. Another example of a foundational principal would be for the first law of thermodynamics which is the conservation of energy. The foundational principal for the first law states that energy is conserved and thus we can use this basic concept to formulate a mathematical approach to the first law.
    He then goes on to say such foundational principals don't exist for QM.
    He then explains two different levels of interpretation of a theory, 1) how to verify theoretical predictions using essentially mathematical formulas and 2) "on the meta-level, less operational (mathematical) but conceptually more significant, interpretation means an analysis of what the theory implies for our general view of the world … "
    He suggests that on the first level, all interpretations are essentially identical, they lead to the same experimental predictions. But on the second level of interpretation, there seems to be no agreement. The Copenhagen Interpretation is obviously very different from the Many-Worlds Interpretation.
    So what needs to be interpreted is this second level where there are no foundational principals for quantum mechanics.
    There is also an interesting article here regarding Zeilinger's work into the foundational principals of quantum mechanics:
    http://www.quantum.univie.ac.at/links/newscientist/bit.html [Broken]
    Last edited by a moderator: May 2, 2017
  17. Oct 12, 2005 #16
    I see. And the fairies at the bottom of my garden are a revelation to me. But pointless nevertheless.
    With respect, if you have no way of explaining a particular phenomenon of the physical world (such as the results of delayed choice experiments) then you have no rational basis for rejecting a possible explanation (the transactional interpretation of QM).
  18. Oct 12, 2005 #17
    OK, I follow this (I think). And I tend to agree (with reservations). There is (to my mind) a "partial" foundational principle (or one could say there is the beginnings of a foundational principle) for QM, and that is the fact that all mass/energy is quantised (the fundamental principle which allowed Planck to explain blackbody radiation and lay the basis for quantum theory in 1900). The problem is that this principle (the fact that all mass/energy is quantised) is apparently not sufficient to generate all of the weirdness of QM. We need something more. In the early decades of the 20th century Bohr added the principle of complementarity; Heisenberg added the principle of uncertainty; Pauli added the exclusion principle, and all of these principles are intertwined in QM. More recently Bell/Aspect and others have added the principle of entanglement. But still all of this is insufficient to arrive at a complete foundational principle for QM.
    imho, "verifying theoretical predictions using mathematical formulas" (the "shut up and calculate" approach) does not constitute an "interpretation".
    imho this is closer to what most people mean when they talk of an "interpretation".
    Let me use the analogy of learning a hypothetical foreign language, such as Klingon. One could learn how to spell all of the words in Klingon (but WITHOUT knowing what these words mean in English), learn all of the grammatical principles and rules and syntax that allow us to combine these non-understood words together to form legitimate Klingon sentences, and on this basis one could then construct valid and legitimate sentences in Klingon, WITHOUT KNOWING WHAT THE SENTENCES MEAN IN ENGLISH.
    The "interpretation" provided by Copenhagen, and even worse the "shut up and calculate" approach, is imho the equivalent of learning how to construct valid Klingon sentences without knowing what these sentences mean in English.
    What we need imho is an interpretation of QM which is equivalent to constructing sentences in Klingon and at the same time being able to translate those sentences into a language that we do understand (which Copenhagen does not do). What does this mean in practice? It means being able to find models and/or analogies which allow us to translate the maths of QM into meaningful ideas/pictures/representations that we can relate to, that provide us with the meaning and understanding of the underlying ontology. It has been the apparent impossibility of doing this over the last 100 years of QM that has prevented us from arriving at such an interpretation.
  19. Oct 12, 2005 #18
    Having thought about this a bit more, I now delete Decoherence from my list of possible interpretations. Decoherence explains the phenomenon known colloquially as "collapse of the wavefunction", but it does not provide a complete interpretation of QM, therefore imho does not qualify on its own as an interpretation (although it could form the basis for an interpretation).

  20. Oct 12, 2005 #19
    I think this is a little bit unfair. I'm not insisting that aspects of the universe can be impenetrable to experiment indefinately, but shut-up-and-calculate would be plain wrong if we can expose the underlying mechanism behind quantum mechanics. Doesn't shut-up-and-calculate raise the issue of penetrability and isn't this a valid and interesting question?

    No I don't. The transactional interpretation is quite valid, and I like I say, I have flirted with it a bit in the past.
  21. Oct 12, 2005 #20
    Yes, I apologise for that. I was being far too flippant.
    But with respect, it seems to me that impenetrability at the quantum level is logically inevitable and should not really be a surprise to anyone. Even with no knowledge of QM, Planck's constant and Heisenberg's uncertainty principle, it is logically quite clear that the classical experimental paradigm (viz the "observer" can always be totally isolated from the "observed") must break down at some point as we go to finer and finer observations.
    however I do in fact believe that aspects of the universe will be impenetrable to experiment for ever - for the reasons above.
    imho shut-up-and-calculate (suac) is perfectly fine for the purpose intended, which is for making quantitative predictions of quantum behaviour where such predictions are possible. However, to my mind "suac" does not constitute an interpretation of QM. Because it is not an interpretation, 'suac' avoids the issue of penetrability.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook