I have two questions about superdeterminism: Does superdeterminism allow for free will? Is superdeterminism a viable interpretation of quantum mechanics?
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3A prior question to answer might be whether "free will" is a scientific concept, and if so, how exactly it is characterised in scientific terms. – Steve Oct 17 '22 at 09:12
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See Hossenfelder & Palmer 2019 and Hossenfelder 2020 (preprint). – Galen Oct 17 '22 at 15:55
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For something in video format, see Does Superdeterminism save Quantum Mechanics? Or does it kill free will and destroy science? and Sabine Hossenfelder on Rethinking Superdeterminism of Quantum Mechanics. – Galen Oct 17 '22 at 16:02
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@Galen Even the title of that paper is already misleading. Quantum mechanics doesn't need saving. It is the best tested theory in all of physics. Superdeterminism tries to save classical mechanics and it does it in a completely unscientific manner. – FlatterMann Oct 17 '22 at 19:21
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@FlatterMann You mean one of the videos, rather than a paper, I suspect. I think the title is misleading, and quite typical of clickbait titles on YouTube. – Galen Oct 17 '22 at 19:35
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@FlatterMann Superdeterminism isn't trying to do anything per se, but sure, people have motivations for raising it. I suspect this title is alluding to the measurement problem, and it does give an impression that QM is in a horrible state of affairs whereas you and I agree it is not. – Galen Oct 17 '22 at 19:36
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@Galen Yes, I generally tell people not to believe anything they see about physics on YT and send them directly to SE. Most of the stuff on YT is just complete nonsense, especially about quantum mechanics. – FlatterMann Oct 17 '22 at 19:39
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@Galen There is no such thing as a measurement problem. Experimental physicists are literally doing many trillions of perfectly well defined physical measurements on quanta every day. There are fundamental misunderstandings about the physical ontology of the Copenhagen interpretation and the actual physics behind it, though. I suspect many of them go back to von Neumann, who understood the mathematics just fine, but is an awful teacher when it comes to actual physics. Happy to discuss in chat, if you want. This is a discussion beyond the comment section. – FlatterMann Oct 17 '22 at 19:41
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Let us continue this discussion in chat. – Galen Oct 17 '22 at 19:56
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@FlatterMann measurement problem isn't about some problem with actual measurements. It is an inconsistency in the quantum theory, where we can't describe the measurement process itself consistently with our understanding of it and with principles of quantum theory like linearity, Schr. equation. However it is true that for many people, this problem does not matter. – Ján Lalinský Feb 17 '23 at 14:51
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@JánLalinský There is no inconsistency in the Copenhagen interpretation. It clearly spells out that two different kinds of processes are necessary to describe quantum mechanical systems: reversible dynamics that is usually represented by the Schroedinger equation (or a Heisenberg formulation) and irreversible processes that take quanta of energy out of the system and which are represented by the Born rule. The "measurement problem" is simply the irrational belief that the Born rule is not an actual part of the theory but merely a kludge. It isn't. It's just as central as the SE. – FlatterMann Mar 25 '23 at 18:56
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@FlatterMann And these two processes are inconsistent with each other. They predict different evolution of the quantum state. – Ján Lalinský Mar 25 '23 at 22:05
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@JánLalinský There is no further evolution of the quantum state after we have taken the energy of the quantum out of it. It's destroyed. What is supposed to be inconsistent here? – FlatterMann Mar 26 '23 at 01:31
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@FlatterMann E.g. measurement of atom's spin component along the axis $z$ by letting the atom move along the axis $x$ in non-uniform magnetic field. The Schroedinger-Pauli equation predicts continuous change of the spin state in time as the atom moves in the magnetic field, and this spin state determines definite value of any projection of spin; it is a number from a real interval (with infinity of possible values). The Born rule allows only eigenvalues of the corresponding operator $\sigma_z$, e.g. two discrete values. Real measurement reveals that only two values are possible. – Ján Lalinský Mar 26 '23 at 02:01
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The Copenhagen interpretation doesn't claim that the wave function is measurable. It only claims that the projections are measurable. The outcome of such a projection is always a quantum of energy. See e.g. Stern-Gerlach. What about that is not clear to you? A good textbook on atomic physics usually contains enough information on how to translate the solution theory of the SE etc. to actual experiments. – FlatterMann Mar 26 '23 at 19:24
4 Answers
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- Does superdeterminism allow for free will?
In this respect superdeterminism is identical with classical determinism as displayed by physical theories such as Newtonian mechanics, Newtonian gravity, Maxwell's electrodynamics, Einstein's general relativity. Everything that happens, including human actions, is determined by the initial conditions + physical laws. Superdeterminism does not add anything to that. If you are a compatibilist, you can accept superdeterminism, no problem.
2.Is superdeterminism a viable interpretation of quantum mechanics?
Superdeterminism is a class of theories which claim that, in a Bell test, the hidden variables and the settings of the detector are pre-correlated in some way. Some such theories could be successful in reproducing QM, some not, so it's not possible to give a general answer. There are some proposed superdeterministic models such as:
A. 't Hooft's cellular interpretation:
Explicit construction of Local Hidden Variables for any quantum theory up to any desired accuracy (not yet published)
https://arxiv.org/abs/2103.04335
Fast Vacuum Fluctuations and the Emergence of Quantum Mechanics
https://arxiv.org/abs/2010.02019
Found Phys 51, 63 (2021)
B. Stochastic electrodynamics (not advertized as superdeterministic, but it is):
Stochastic electrodynamics and the interpretation of quantum theory
https://arxiv.org/abs/1205.0916
E.Santos: Realistic interpretation of quantum mechanics, Cambridge Scholars Publishing, 2022. Chapter 5
This theory was successful in reproducing many so-called "uniquely quantum" phenomena, like black-body radiation, specific heat of solids, and to a limited degree, the stability of atoms.
C. Invariant set theory:
Rethinking Superdeterminism
https://arxiv.org/abs/1912.06462
Front. Phys. 8:139 (2020)
Bell's Conspiracy, Schrödinger's Black Cat and Global Invariant Sets
https://arxiv.org/abs/1502.06972
Phil. Trans. R. Soc. A, 373, 2015.
As far as I know there is not much debate around any of these models, none of them is accepted as "mainstream" but they are not proven wrong either. So It's hard to say how successful they really are. Time will tell.
Andrei
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All stochastic models are trivially wrong because of the fluctuation-dissipation theorem. – FlatterMann Oct 19 '22 at 11:20
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The first question is more related to philosophy rather than physics, however the second one touches the matter of interpretations of quantum mechanics. For the first question, it varies from philosophical interpretation of will itself. However advocates for determinism also advocate for no free will. There is no free will in determinism. Super-deterministic interpretation of quantum mechanics had its supporters, notably Einstein with hidden variables postulation. However, this was quantum mechanics allows pure statistical randomness to occur. This test for whether Albert Einstein was correct about his hidden variables or no was done in the name of Bell test. According to Bell's speculation, if the universe actually functions in accord with any theory of hidden variables as Einstein postulated, then the results of a Bell test will be constrained in a quantifiable way, which it was not. Henceforth any real deterministic approach to quantum mechanics, other than some interpretations such as Bohemian mechanics and more, were essentially disregarded and the Copenhagen interpretation was the dominant consensus.
ludwigvan
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6Superdeterminism is actually a loophole in the Bell test. It allows for local hidden variable theories which violate the Bell constraint – Ryder Rude Oct 17 '22 at 03:45
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What JS Bell showed was that Einstein's "local realism" was untenable, and that only non-local realist theories could explain QM. The DeBroglie-Bohm interpretation is an example of the space that remains. – Steve Oct 17 '22 at 09:20
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1@RyderRude, I can't claim to fully understand "superdeterminism" or how it differs from ordinary determinism, but whilst it preserves a space for "local realism", it does so only by undermining other assumptions which local realists (and all others) would have been loath to relinquish. That assumption is broadly that there are so many variables involved in the setting of the experimental apparatus, that to believe it can be traced back only to the same cause as the local variables which the experiment is measuring, is inconsistent with how we understand multi-variable causation to work. – Steve Oct 17 '22 at 09:52
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@Steve Ordinary determinism already has lack of free will. Superdeterminism is just ordinary determinism plus the conspiracy that some demon has fine tuned human choices to make quantum mechanics look like the correct theory, or that the choices are fine tuned by chance. See the answer here. It's a silly loophole that undermines Bell's theorem for no reason. Non-local hidden variables are much preferable to local-hidden variables plus superdeterminism – Ryder Rude Oct 17 '22 at 10:06
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@RyderRude, agreed. Shorn of any mystical or supernatural aspect, it either implies that there are far fewer variables (or fewer states which those variables can assume) than we traditionally suppose, or it implies that there is some mechanism which deterministically coordinates those states and which doesn't correspond to any known characterisation of cause and effect. The first alternative could probably be dismissed with evidence - that we are supposing no more variables than necessary to explain what we actually see. (1/2) – Steve Oct 17 '22 at 10:35
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The second alternative probably cannot be defeated logically, but it would seem to pose the existence of a substructure of reality whose complexities, whilst mechanistic, must be so great as to be beyond comprehension to humanity, and therefore a dead end in terms of any explanatory or predictive power. For now at least, there are other areas still to be searched. There is no scientific value in adopting positions which demonstrate the hopelessness of further enquiry, so long as valid positions of hope remain. (2/2) – Steve Oct 17 '22 at 10:36
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1@RyderRude, indeed thinking more on this, this "superdeterminism" is probably most preferred by anti-scientific forces, since it avoids denying determinism in principle, but it does invite us to hold that it must be an unknown, and perhaps even unknowable, mechanism by which the world is determined and such seemingly bizarre correlations occur. Accepting this invitation helps to rescue their preferred theory - whether it be the controlling deity or the soul of the religious, or the individuality and free will of the liberal - from the jaws of science and rational enquiry as we know it today. – Steve Oct 17 '22 at 10:48
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1@Steve Agreed. And there is no reason we should be hating non local realism and determinism in the first place, if it can be made consistent with relativity. The price of saving locality using superdeterminism is too huge. Plus superdeterminism has no mathematical basis. It's only a claim that some model might be able to do it. That model will have to explicitly involve the postulate "Humans must be fooled". It's the worst interpretation of quantum mechanics. – Ryder Rude Oct 17 '22 at 11:07
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Ryder Rude, are you familiar with 't Hooft's cellular automaton model? Or with Stochastic electrodynamics? None of them postulates "Humans must be fooled", and humans are not actually fooled. What happens is that human actions, like everything else, is predictable in a deterministic theory, so you cannot "surprise" nature by your actions. – Andrei Oct 18 '22 at 11:28
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@Andrei Stochastic theories should generally predict that the universe is opaque. In reality we can see almost all the way to the big bang. These things are IMHO so trivially wrong that they are not even worth mentioning. – FlatterMann Oct 19 '22 at 09:03
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Contrary to its name, Stochastic electrodynamics is not actually stochastic. The EM field associated with all charges in the universe, the zero-point field, evolves deterministically according to Maxwell. But since there is no way to get its detailed description, it's assumed to be stochastic, to enable practical calculations. – Andrei Oct 19 '22 at 10:17
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@Andrei If the field is stochastic then you are being sunk by the fluctuation-dissipation theorem. – FlatterMann Oct 19 '22 at 11:24
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As I said earlier, the field is not stochastic, it's just approximated to be so to simplify the calculations. – Andrei Oct 19 '22 at 13:44
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@Andrei Then the approximation is sunk by the fluctuation-dissipation theorem. Stochastic interpretations of quantum fields can't work and they aren't being observed in nature. – FlatterMann Mar 26 '23 at 19:52
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@FlatterMann, the field in Stochastic Electrodynamics is not quantum, is the classical EM field. Anyway, can you point me to some paper where your argument, that stochastic models are wrong is presented in some detail? – Andrei Mar 27 '23 at 06:28
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Classical stochastic electrodynamics is usually just called "noise". It's still subject to the fluctuation-dissipation theorem. At the end of the day you (or, better, the originators of this model) seem to be redefining terms here. – FlatterMann Mar 27 '23 at 16:38
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Superdeterminism allows for a reformulation of free will. The Creator can predetermine a universe that exhibits what the Creator already knows what your freely willed decisions would be. This theory of free will under superdeterminism is called cinematism. Superdeterminism is an underlying theory in itself which explains quantum mechanics. However, one can also posit a superdeterministic interpretation of quantum mechanics at least. You should be aware that there are two fundamentally different versions of superdeterminism. The first version is based on hidden variables. The second version simply says that the universe is a predetermined static block reality without continuous causation in physics, essentially poking a hole in a little known fourth assumption underlying Bell’s Inequalities. This second version has been proven by Dr. Johan Hansson at Physics Essays Vol. 33, No. 2 (2020).
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One can "explain" quantum mechanics fairly easily with relativity. It doesn't require any effort along the lines mentioned here. There are no hidden variable theories. Nobody has ever proposed one, let alone one that makes any relevant physical predictions. I general most of these things spring from the desire to somehow "save" classical mechanics. We have known since the 19th century that classical mechanics is not even compatible with the existence of stable matter. It's simple not a good theory. No need to waste any further effort on it. – FlatterMann Mar 26 '23 at 19:57
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Both superdeterminism and free will are nonsensical terms that philosophers like to amuse themselves with. "Superdeterminism" is basically just a variation on "god did it" after we strip off the supernatural aspect. Superdeterminism can explain absolutely everything, which means that in reality it explains absolutely nothing. Free will, on the other hand, is simply not a testable concept. Reduce it to the question "Chocolate or Vanilla?" and you will notice that the only time you can make a "free" decision in your life is before you have tasted either of these two flavors. The second time around you already know whether you like one or the other better and hence your decision is not free. Of course the first time around your decision is simply a random choice exactly because you don't know anything about your preferences, yet.
The far more interesting question concerns "interpretations of quantum mechanics". That is indeed a boondoggle that physicists have gotten themselves into. I would suggest to you to look at the structure of the "Copenhagen interpretation" very carefully if you are interested in this "problem". It didn't just happen by "random" reasoning and it is not easily replaceable with a somehow equivalent framework that uses different terms to arrive at exactly the same conclusions. Instead Copenhagen tries to teach a very important lesson about reality, which bisects into two different kinds of physical processes: reversible and irreversible ones. The free propagation of the quantum mechanical ensemble is a reversible process that happens in isolation from the environment. It can be described in many ways, the best known and most simple one to compute is the Schroedinger equation. And then there is a second kind of process in which quantum mechanical systems couple to their environment and which is dominated by the irreversible exchange of energy, momentum, angular momentum and charges. We call this the "preparation" and "measurement" processes and they are being described by the Born rule.
So if you want to take a piece of "ontological" advice: before you jump on the bandwagon of a non-Copenhagen interpretation, do a sanity check and ask the obvious question: "Does the new interpretation acknowledge the existence of reversible/irreversible interactions and their fundamental difference?". If it does not, then it is not an equivalent interpretation to begin with and in all likelihood it will fail to provide the correct physical analysis in at least some cases.
FlatterMann
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2"Superdeterminism is basically just a variation on 'god did it'" - I don't think that is an accurate representation of any writing I have seen on "superdeterminism". The "super" in superdeterminism was supposedly to emphasise the degree of determinism, not to imply that the supernatural was involved. – Steve Oct 17 '22 at 09:14
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@Steve Superdeterminism is the vague philosophical concept that it doesn't matter what we are measuring because all measurements are biased in such a way that we will get a specific (deceptive) result anyway. It is the physics equivalent of the anti-evolution response "the devil put them bones in them hills". It is not even a scientifically testable hypothesis by any standard. You could call it the intellectually empty last stand of classical physics. It is also not needed. Classical physics is a limiting case of quantum mechanics. We can reproduce it just fine. Just not the other way around. – FlatterMann Oct 17 '22 at 18:52
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You have no idea what you are speaking about. Superdeterminism is just the denial of the statistical independence assumption in Bell's theorem. It means that the hidden variable and the detector settings are not independent parameters. This can be the result of any type of physical interaction (electromagnetic, gravitational). It has nothing to do with "god did it" which is more representative for Bohr-Copenhagen philosophy. – Andrei Oct 18 '22 at 10:48
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@Andrei Copenhagen represents the trivial reality of quantum systems. Now, I admit that most textbooks that contain the von Neumann formalism don't tell you the "why it is so", but that is a problem of the textbooks, it's not a problem of Copenhagen. Happy to discuss in the chat if you are actually interested. Superdeterminism is simply not a testable scientific hypothesis. It basically tells you that your experiment has to say "green" because some magical initial setting before the big bang says so. That's religion, not physics. – FlatterMann Oct 18 '22 at 14:24
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FlatterMann, I'd like to discuss in the chat but I don't know how. My problem with Copenhagen is its non-locality, not it's inability to answer "Why" questions. Superdeterminism is as testable as any other physical theory. In fact, classical electromagnetism, as it is, is a superdeterministic theory. It imposes some constraints (Maxwell's equations need to be satisfied) that are disregarded by Bell's independence assumption. The so-called "classical prediction" (inequality not violated) is incorrectly assessed due to the failure of satisfying those constraints. – Andrei Oct 19 '22 at 07:46
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@Andrei: Copenhagen is not "non-local". You can look at the equations of quantum field theory (which are the ones that really matter) and you will find that they are perfectly local. What they are not is separable, but that is a completely independent concept. Locality is a spacetime property. Separability is about the behavior of the ensemble in Hilbert space. Maxwell's equations are statistical averages of classical EM field states. They don't tell us anything about quantum effects. Bell does not mean that averages can't be classical and classical physics does not require superdeterminism. – FlatterMann Oct 19 '22 at 07:57
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I you want to chat, you can do it in this old chat room: https://chat.stackexchange.com/rooms/139887/is-qm-really-inconsistent – FlatterMann Oct 19 '22 at 08:15
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QFT does not present a local description of measurement (collapse) in the EPR setup. Read any textbook on QFT and you will find a lot of hand-waving at this point. Outside measurement, QFT is local, but it's not enough. Copenhagen makes the assumption that the outcome of a spin measurement is fundamentally random. The probability for 2 such measurements in the EPR setup to agree is 0.5. We have 1. Therefore both measurements can't be random, but since they are space-like we need an instantaneous signal from the first lab to reach the second. QFT does not answer that. Copenhagen is non-local. – Andrei Oct 19 '22 at 08:15
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Copenhagen doesn't make any "assumptions". It simply describes what experimentalists are observing. One could, of course, revolutionize physics by providing a formula for the time of arrival of the next photon in a photomultiplier tube. Nobody has been able to provide us with such a formula and the arrival times are completely random for sufficiently uncorrelated sources. Measurements in an EPR setup are correlated, but they are still random at each end. That is not a contradiction but it stresses your intuition about the difference between individual quantum systems and the ensemble average. – FlatterMann Oct 19 '22 at 08:31
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You cannot observe if a spin measurement result was predetermined or not. But you can deduce, from the locality assumption that it has to be predetermined. It goes like this: You measure one particle at A, you get +1. Locality implies that your measurement at A cannot change the state of B (measurements are space-like). But QM tells us that the A measurement collapsed the state of B to -1. But if the state of B is -1 after the A measurement, and the state of B did not change it logically follows that B was -1 even before the A measurement, so the result was predetermined. – Andrei Oct 19 '22 at 10:25
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There is no reason you should expect to have a formula for the arrival times because you do not know the initial state in microscopic detail and you do not have the computing power to solve the system even if you somehow knew the initial state. – Andrei Oct 19 '22 at 10:28
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