• Marchesk
    759
    This interpretation eschews the entire Copenhagen framework which has led to the other interpretations. It seeks to be rid of all the spooky weirdness the various experiments have inspired. So no fundamental indeterminism, no pilot waves, no non-locality, no other worlds, and no weird collapse.

    The claim is that uncertainty about the exact state of the measuring device is being ignored in the experiments, because we can't model that kind of complexity. This uncertainty gets entangled with the resulting measurement in the experiments.

    So a measuring device is made up of many atoms which has an exact quantum state. This state is classical, in that all the properties are well defined. The problem is that we can't measure the exact state of something made up of many particles, because that would involve an enormous number of measurements. So we just set aside that issue when doing experiments.

    But, because the particles used in the experiment are so small, the act of detecting has a large influence on the resulting measurement. Thus, our uncertainty about the exact quantum state of the measuring device is transferred to uncertainty about the experiment. Thus, we end up with a probability distribution of what the property of some particle being measured will be, because every time the experiment is run by someone, the measuring device is in an unknown, but different quantum state.

    So why does the wave function describe the experiment results? Because the electron gun, for example, creates an excitation in the quantum field, and if we knew the exact molecular arrangement of the detection screen, then we could 100% predict where the electron would hit. The excited quantum field in conjunction with the molecular arrangement of the screen deterministically determine a singular result. We just can't precisely measure the molecular arrangement of the screen.

    This is the view (as best I can paraphrase it) put forward by James Binney, physics professor at Oxford.

    Do you think this sort of approach is viable? Can it resolve the weirdness of QM by explaining it away in classical terms? Has all the woo of QM been a big mistake?
  • Hanover
    987
    The problem with indeterminism as currently defined (exact sets of causes can have variable effects) is incoherent to me. It seems to violate basic causation, a fundamental concept for our comprehension of the world (ala Kant). So, my inclination is to accept any expert's rejection of QM indeterminism just because all else is incomprehensible.
  • TheWillowOfDarkness
    1.1k
    The issue is that basically claims non-locality. If our problem is an inability to locate particles, then our local space is defined by something else, by things which cannot be pinpointed in our immediate vicinity.

    It also effectively claims a hidden variable: if only we knew this hidden state we can never know about, then we could recognise how an electron was pre-determined to hit the screen.
  • Agustino
    4.2k
    What's the QM problem? Why is it a problem that the result is indeterministic (better said probabilistic)?

    And no I don't think that approach is valid. If you don't know the quantum state of the measuring device, then how will it help to add another measuring device measuring that one, and hence changing its quantum state? :s
  • Marchesk
    759
    The issue is that basically claims non-locality. If our problem is an inability to locate particles, then our local space is defined by something else, by things which cannot be pinpointed in our immediate vicinity.

    It also effectively claims a hidden variable: if only we knew this hidden state we can never know about, then we could recognise how an electron was pre-determined to hit the screen.
    TheWillowOfDarkness

    No, because he's basically rejecting point particles in favor of a quantum fields. The fields have wave-like properties. When they interact with something like a detector, then the exact quantum state of that detector determines the exact measurement. A particle is just a certain kind of excitation of the quantum field.

    As such, there is no need for any hidden variables or non-locality.
  • Marchesk
    759
    What's the QM problem? Why is it a problem that the result is indeterministic (better said probabilistic)?Agustino

    There's a better way to state the problem. The Schrodinger equation doesn't show any sort of "collapse" to a single outcome, which is based on a probability. No quantum system is like that. But we get that when we decide to measure for something.

    So why should a measurement, which is done by a physical device that is presumably made up of the same sort of quantum particles, result in a zeroing out of all other possibilities in the wave distribution to one single actuality?

    That's the motivation for Many Worlds, btw. It removes the collapse issue, but at a cost of postulating a vast number of branching worlds that we can't interact with. But if you're willing to roll with that, it works.

    Or you could do what Binney has done, and question the assumption that the Schrodinger Equation must be modelling something real. His position is that it's a useful tool, but it has properties which are fantastical and unreal. And he avoids ducking the question that instrumentalists do, or proposing some form of idealism, which Bohr may have preferred. Instead, he favors one, classically real world.
  • Marchesk
    759
    The problem with indeterminism as currently defined (exact sets of causes can have variable effects) is incoherent to me. It seems to violate basic causation, a fundamental concept for our comprehension of the world (ala Kant). So, my inclination is to accept any expert's rejection of QM indeterminism just because all else is incomprehensible.Hanover

    There is an entirely different possibility, ala Kant. The real world is very different from our ability to conceive it, and the rubber meets the road at QM, where we find out the truth of our limitations.
  • Agustino
    4.2k
    That's the motivation for Many WorldsMarchesk
    There's also Pilot Wave theory which removes the non-determinism and collapse issue, but at the cost of non-locality. The theory is quite simple in that it supposes that each particle interacts with a guiding field. So, say, the particle always passes through one of the slits in the double slit experiment, but the wave passes through both and hence interferes with the particle's motion.
  • Rich
    288


    I am not sure about De Broglie's views, but Bohm is quite clear in his own book, that his model, which he shares with De Broglie is casual but not deterministic. I find this error repeated in many books and websites, which makes me wonder whether they have ever read the source material or if they are all just repeating the same error.

    From Science, Order and Creativity

    "This shows the interpretation, while being causal is not strictly deterministic. [Bohm's italics]. Indeed in the next chapter it will be shown that the possibility is opened for creativity to operate within a causal framework."
  • Agustino
    4.2k
    "This shows the interpretation, while being causal is not strictly deterministic. [Bohm's italics]. Indeed in the next chapter it will be shown that the possibility is opened for creativity to operate within a causal framework."Rich
    Not "strictly" deterministic. He qualifies the statement, and that's because he has a spiritual axe to grind.

    De Broglie's viewsRich
    De Broglie did qualify it as causal and deterministic, although the scientist could never predict it, because there would be no way to know the particle's position without interfering with it (and with its guiding field) by measuring it.
  • Gooseone
    70


    It sounds a bit like the hidden measurement interpretation (https://en.wikipedia.org/wiki/Hidden-measurements_interpretation)

    A bit off topic but since we're talking QM woo, does anyone have any idea if the double slit has been carried out with two double slits? If the wave function would be more fundamental than a particle state and such (hidden measurement) an interpretation is correct, the measuring could "collapse" the wave function but the first double slit generates an interference pattern, a second double slit could potentially generate interference to show things having become wave like in nature again.
  • Rich
    288
    What Bohm was able to do, and what De Brogle could not figure out how to do, was build a casual, real model for QM that had an ontological basis. But to do this, be had to introduce a Quantum Field (which he later called a holomovement) that is totally undefined.

    So what is a Quantum Field? Well for one thing, it is probabilistic in nature. Or as Bohm preferred, it contains possibilities. From this, he proceeded to delve deeper into the meaning of this by considering the nature of creativity and intuition. This, he presents a full ontological model that is real, casual, and not strictly deterministic. He never actually goes so far as to equate his notion of creativity with Bergson's Elan Vital, but he nudges as close as he could to it while still not saying anything that might jeopardize his job. The Copenhagenists were forever on his case, doing everything they could to marginalize his theory. Bell was an enough of a renegade to resurrect it.

    It can also be pointed out that De Broglie, in an essay about Bergson's philosophy, spoke quite positively of Bergson's thoughts and how they pre-dated but in many ways predicted quantum physics. It is quite a nice essay.
  • tom
    780
    There's also Pilot Wave theory which removes the non-determinism and collapse issue, but at the cost of non-locality. The theory is quite simple in that it supposes that each particle interacts with a guiding field. So, say, the particle always passes through one of the slits in the double slit experiment, but the wave passes through both and hence interferes with the particle's motion.Agustino

    There are bigger costs than non-locality. The theory doesn't work. It can't be made relativistically invariant, requires absolute time, and is restricted to the position basis. Now, there are attempts to get round these (and other) issues, but as things stand quantum field theory doesn't work in this interpretation.

    There is also a slew of results that refute hidden-variable theories of any kind, not least the Free Will Theorem.
  • tom
    780
    That's the motivation for Many Worlds, btw. It removes the collapse issue, but at a cost of postulating a vast number of branching worlds that we can't interact with. But if you're willing to roll with that, it works.Marchesk

    That's not a postulate of Everettian QM, it's an inevitable consequence.
  • Rich
    288


    That it cannot be made relativistically invariant is a positive. Time as define in Relatively and Einstein is a mess with all of its sci-fi inducing paradoxes, and should be jettisoned.
  • Agustino
    4.2k
    There is also a slew of results that refute hidden-variable theories of any kind, not least the Free Will Theorem.tom
    :s
  • Marchesk
    759
    Sure, what I mean is that it's a pretty big metaphysical bullet to bite.
  • Rich
    288
    One of the "refutations" of Bohm's theory?

    http://advances.sciencemag.org/content/2/2/e1501466
  • Hanover
    987
    My reference to Kant was as to the synthetic apriori status of causation, but not as to the true nature of reality, as that would be nuemonal. Asserting that QM is the neumona would misunderstand Kant because the neumona is definitionally unknowable.
  • TheWillowOfDarkness
    1.1k


    The point it's equivalent in the context of observation and description. We can't get past uncertainty to give a description of the (pre)determined future. With respect to our capacity to describe what's going on, the exact and unknown quantum state we can't measure is of no more use to us than a non-local state.

    In terms of descriptive power, the exact state we don't know might as well be in some other galaxy. We don't have description of it which allows us to tell the future which must necessarily occur.
  • tom
    780
    Sure, what I mean is that it's a pretty big metaphysical bullet to bite.Marchesk

    It's not metaphysical in the slightest, it's the real physical situation. And, the other worlds are required to explain what we see in this world in terms of interactions with them - i.e. it is a testable prediction.
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