111–120 of 132 posts
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What you describe is "quantum contextuality". What Sabine is saying is that so-called superdeterminism/giving up statistical independence implies the contextuality that is needed to explain quantum mechanics using hidden variables, and it does so in a simple way if we accept future input dependence.
Bell nonlocality is not the exact same thing as contextuality from what I’ve been able to find.
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You might be interested in some code that illustrates the problem of hidden variables and the EPR paradox: https://pastebin.com/J4ZUhG8e . The issue is that we can't replicate what QM predicts (and experiments validate) using hidden variables without additional steps or assumptions. For example, in that code, there are a few possible ways we could still produce the QM correlation function with local hidden variables:…
> 3. We could bias the initial sampling of our hidden variables. The problem is, this requires that we know the setting of the detector ahead of time. The standard computational approach to this is to define the distribution as lazily evaluated based on some future state. That's exactly what Sabine is suggesting for a superdeterministic theory. > It essentially means that all QM experiments have predetermined outcome…
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> There is an additional postulate, namely that the state vector is the real world we inhabit. This may seem obvious to you and not amount to postulating much or anything with any substance, but that's a philosophical claim that isn't suggested by the physics. Any interpretation has to postulate that something "is" the real world, in that sense. Postulating that there's an additional entity dependent on the wavefunct…
> Postulating that there's an additional entity dependent on the wavefunction that "is" the real world (as e.g. pilot-wave theories do) is violating Occam's Razor. Not really, because in Bohmian mechanics the wave function is nomological, ie. not real, and merely describes a law of motion. Bohmian mechanics is kind of the dual of many worlds in this sense, and so requires no more postulates. > There are, but again, a…
I don't see that that's a meaningful/objective distinction? The wavefunction is certainly physically meaningful in the sense that you can't predict experimental results without computing its behaviour (or something equivalent to it). I don't think that you can reduce your number of postulates by declaring parts of your theory "not real" - given that elementary particles are not directly observable, couldn't we just declare that e.g. electrons are "not real" and merely describe a law of experimental results?
> Since you mentioned Bohmian mechanics, the Born rule was derived from the postulates a long time ago
It's not really derived, rather something equivalent to the Born rule is included as one of those postulates. At some point you have to go from wavefunction to probability distribution, and you either make the rule for that an outright postulate or have some plausible but unsatisfactory argument about how dynamical evolution makes this the "right" rule. Different interpretations do this at different points, but they all have to do it somewhere.
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It forms a weaker interference pattern - imagine superimposing 50% of the interference pattern and 50% of the non-interfering look. There's also the fun of the delayed-choice quantum eraser experiment, where if you measure (or not) which slit the photon went through after measuring the interference pattern (or not), you see (or don't see) the interference pattern.
Ok, that's definitely not what OP said. Of course the particle still can interfere with itself after the slit, it's just that when the measurement is made, the pattern of two waves interfering gets much weaker/non-existent. Also, the experiment you are alluding to does not say what you think it says. Perhaps you will be interested on another video from Sabine. https://www.youtube.com/watch?v=RQv5CVELG3U&ab_channel=Sa…
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It's still conspiratorial. You just happened to choose the right particles to measure? It makes a mockery of the idea of trying to do science at all - the experiments you take are already determined, you can't learn anything about what causes have what effects because you can't ever change a causal variable.
> It makes a mockery of the idea of trying to do science at all - the experiments you take are already determined The laws of physics were there before people started studying physics. Didn't make it less interesting for those who were interested. Everything we do is a mockery - life expectation is 75 if you are lucky and universe doesn't care about your achievements >you can't learn anything about what causes have w…
But they're interesting because they are laws - because there's some structure there, because the same causes consistently have the same effects. Superdeterminism denies all that.
> If you don't have free will, then how can you change smth?
I'd say that if you're an inherent part of the causal chain that makes something happen then it's fair to say that you changed it. You don't have to assume free will to acknowledge that we affect our environment.
> What part of a computer "learns" during gradient descent?
I don't know or particularly care, but the learning happens - you can't understand the behaviour of the system otherwise.
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I do, it's called "quantum mechanics". It's the most thoroughly verified theory in the history of physics, and in my subjective opinion the most mathematically beautiful one. It is the greatest pinnacle of human scientific achievement. But people think the idea that things might superimpose on each other like waves is weird, it's not what they see everyday objects that are 10,000,000,000x larger behaving, so it can't…
What’s going on with gravity though? Actually, did they decide if the holographic principle is true yet?
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> Postulating that there's an additional entity dependent on the wavefunction that "is" the real world (as e.g. pilot-wave theories do) is violating Occam's Razor. Not really, because in Bohmian mechanics the wave function is nomological, ie. not real, and merely describes a law of motion. Bohmian mechanics is kind of the dual of many worlds in this sense, and so requires no more postulates. > There are, but again, a…
> Not really, because in Bohmian mechanics the wave function is nomological, ie. not real, and merely describes a law of motion. I don't see that that's a meaningful/objective distinction? The wavefunction is certainly physically meaningful in the sense that you can't predict experimental results without computing its behaviour (or something equivalent to it). I don't think that you can reduce your number of postulat…
The wavefunction in Bohmian mechanics is just as interesting and unreal as the Hamiltonian in classical statistical mechanics. Which is to say that, sure, you still need something like it to calculate outcomes and what you observe will conform to it, but that doesn't make it real. The particles are real here, and they just follow a law of motion described by the wave function.
> given that elementary particles are not directly observable, couldn't we just declare that e.g. electrons are "not real" and merely describe a law of experimental results?
Sure, that's what ontology is all about: define what's real (base axioms), and derive what else we observe in terms of what you consider real. This needs to fit into a coherent total picture, and you want one that's general and parsimonious.
For MWI, the wavefunction is real and the grooves are real worlds that evolve in parallel, and the particles don't have any independent existence. In Bohmian mechanics, the particles are real and follow a law of motion described by the wave function, but the latter doesn't have any physical existence.
> It's not really derived, rather something equivalent to the Born rule is included as one of those postulates.
I don't think that's correct. To my knowledge, distributions conforming to the Born rule [1] are guaranteed in all but highly anomalous initial configurations, akin to how thermodynamics ensure that entropy always increases except again, in highly anomalous initial configurations. And even for the majority of anomalous distributions, evolution under the Bohmian dynamics is very likely to converge to the Born rule anyway [2].
Because this quantum equilibrium is a hypothesis and not a postulate, this leaves open the possibility that Bohmian mechanics can be experimentally differentiated from orthodox QM, but no one has figured out a way to actually create such distributions.
Anyway, this is all an interesting academic exercise and I don't think Bohmian mechanics is nearly as problematic as some physicists think, but it's unlikely to go anywhere given the little investment it receives.
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> Well, yes, it's a model for the physical world. Refusing to accept that the state vector is the real world we inhabit is tantamount to rejecting the existence of an objective universe, in which case any discussion is moot Some physicists consider the wave function to be ontologically inadequate to explain the physical world. See the discussion of "bohmian mechanics being many worlds in denial" for some details and…
It may be inadequate, but the consequences of quantum theory still apply without having to add new postulates. Among those consequences is many worlds.
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> 3. We could bias the initial sampling of our hidden variables. The problem is, this requires that we know the setting of the detector ahead of time. The standard computational approach to this is to define the distribution as lazily evaluated based on some future state. That's exactly what Sabine is suggesting for a superdeterministic theory. > It essentially means that all QM experiments have predetermined outcome…
I gotcha. It actually seems obvious and fairly reasonable when you put it that way, since it removes the "conspiratorial" element that theories of superdeterminism seem to invoke.
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> Not really, because in Bohmian mechanics the wave function is nomological, ie. not real, and merely describes a law of motion. I don't see that that's a meaningful/objective distinction? The wavefunction is certainly physically meaningful in the sense that you can't predict experimental results without computing its behaviour (or something equivalent to it). I don't think that you can reduce your number of postulat…
> The wavefunction is certainly physically meaningful in the sense that you can't predict experimental results without computing its behaviour (or something equivalent to it). The wavefunction in Bohmian mechanics is just as interesting and unreal as the Hamiltonian in classical statistical mechanics. Which is to say that, sure, you still need something like it to calculate outcomes and what you observe will conform…
Obviously I'm coming at this from a partisan perspective, but that really does seem like more postulates - either you calculate your wavefunction evolution and predict your experimental results from that or you calculate that same wavefunction evolution, calculate your particle state ensemble from that, and then predict your experimental results from that.
> I don't think that's correct. To my knowledge, distributions conforming to the Born rule [1] are guaranteed in all but highly anomalous initial configurations, akin to how thermodynamics ensure that entropy always increases except again, in highly anomalous initial configurations.
I tried to skim through the 60 page paper but couldn't find the part you're claiming. Most modern presentations of Bohmian mechanics take the probability rule as a postulate. Bohm did initially present it with a statistical fluctuation and dynamical evolution argument, but most people find that unsatisfactory, and you can (and people do!) make the same argument in an Everett-style many worlds setting as well. (Admittedly people tend to find it even less convincing in a probability-branches setting than a particles-following-a-probability-distribution setting, but I suspect that's an artifact of similarity to classical thermodynamics rather than because it's objectively more plausible there).