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Cake day: July 7th, 2024

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  • Technically aether theory was never ruled out. People love to claim that the Michelson-Morley experiment ruled it out, but this is historical revisionism. The MM experiment was conducted in 1887. Hendrik Lorentz proposed his aether model in 1904. Obviously Lorentz was not such a moron he would not take into account the findings of MM, but that is what people are unironically suggesting when they say MM somehow retrocausally ruled out his model. Indeed, both Michelson and Morley did not believe their own experiments ruled it out either but continued to promote such models.

    Lorentz’s aether model and Einstein’s relativity are actually mathematically equivalent so they make all the same predictions, so no possible experiment could rule out Lorentz’s aether theory that would not also rule out Einstein’s relativity. Indeed, if you read his 1905 paper where Einstein introduces special relativity, his criticism of Lorentz’s model is only a philosophical objection. He never posited that an experiment can rule it out. MM only rules out some very early aether models, not Lorentz’s model.

    I would recommend also checking out John Bell’s paper “How to Teach Special Relativity,” where he also discusses this fact, and how the mathematics of special relativity are perfectly consistent with a reality with an absolute space and time. Taking space and time to be relative only comes at the level of metaphysical interpretation.



  • Also Bell experiments have proven the indeterminacy which you say is absurd. No theory of local hidden variables can describe quantum mechanics.

    You say Bell’s theorem disproves realism, but then you immediately follow it up with saying it disproved local realism. Do you see how those two are not the same statements? It never even crossed Bell’s mind to deny reality. He believed that the conclusion to his own theorem is just that it is not local.

    (Technically, anything explained non-locally can also be explained non-temporally instead, so it is more accurate methinks to say spatiotemporal realism is ruled out. I am not as big of a fan of thinking about it non-temporally but there are some respectable people like Avshalom Elitzur who do. Thinking about it non-locally is far more intuitive.)

    Also, again, this is not about indeterminacy and determinacy, but about indefiniteness and definiteness, i.e. anti-realism vs realism. These are not the same things. To say something is indeterminate is merely to imply it is random. To say something is indefinite is to say it doesn’t even have a value at all. It is also sometimes called realism because it’s about object permanence. Definiteness is just object permanence, it is the idea that systems still possess observable properties even when they are not being directly observed in the moment.

    He’s asking where the line is between this indeterminacy and determinacy. At what scale to things move from quantum to “real” and why?

    You could in principle make this non-realism make sense if you imposed some sort of well-defined physical conditions as to when particles take on real values. Bell described this as a kind of “flash” ontology because you would not have continuous definite values but “flashes” of definite values under certain conditions. But it turns out that you cannot do this without contradicting the mathematics of quantum mechanics.

    These are called physical collapse models, like GRW theory, but these transitions are non-reversible even though all evolution operators in quantum mechanics are reversible, and so in principle if you rigorously define what conditions would cause this transition, you could conduct an experiment where you set up those conditions, and then try to reverse it. Orthodox quantum theory and the physical collapse model would make different predictions at that point.

    These models never end up being local, anyways.

    The reason I say value indefiniteness is absurd as a way to interpret quantum mechanics is because it is not necessitated by the mathematics at all, and if you believe it:

    1. It devolves into solipsism if you do not rigorously define a mathematical criterion as to when definite values arise, because then nothing has real values outside of you directly looking at it.
    2. If you do rigorously define a criterion, then it is no longer quantum mechanics but an alternative theoretical model.

    So, either it devolves into solipsism, or it is a different theory to begin with.

    Bell was fine with #2 as long as people were honest about that being what they were doing. He wrote an article “Against ‘Measurement’” where he criticized the vagueness of people who claim there is a transition “at measurement” but then do not even rigorously define what qualifies as a “measurement.” He wrote positively of GRW theory in his paper “Are there Quantum Jumps?” precisely because they do give a rigorous mathematical definition of how this process takes place.

    But Bell also didn’t particularly believe there was any reason to believe in value indefiniteness to begin with. You can just interpret quantum mechanics as a kind of stochastic mechanics, just one with non-local features, where it is random but particles still have definite values at all times. The same year he published his famous theorem in 1964 in the paper “On the Einstein Podolsky Rosen Paradox” he also published the paper “On the Problem of Hidden Variables” debunking von Neumann’s proof that supposedly you cannot interpret quantum mechanics in value definite terms. He also wrote a paper “Beables in Quantum Field Theory” where he shows QFT can be represented as a stochastic theory. He also wrote a paper “On the Impossible Pilot Wave” where he promoted pilot wave theory, not necessarily because he believed it, but because he saw it as a counterexample to all the supposed “proofs” that quantum mechanics cannot be interpreted as a value definite theory.

    My point isn’t about randomness/indeterminacy. It is about “indefiniteness,” the claim that things have no values until you look. This either devolves into solipsism, or into a theory which is not quantum mechanics. It is far simpler to just say the systems have values when you’re not looking, you just don’t know what they are, because the random evolution of the system prevents you from tracking them. It is sort of like, if I hit a fork in the road and take either the left or right path, and you don’t know which, you wouldn’t then conclude I didn’t take a path at all until you look. You would conclude that you just don’t know what it is, and maybe assign probabilities to them. The fact that the probability distribution doesn’t contain a definite value does not demonstrate that the real world doesn’t contain a definite value, and believing it doesn’t unnecessarily over-complicates things. And definite ≠ deterministic. Maybe the path taken is truly random, but there is a path taken.


  • Not to be the 🤓 but just so we’re clear, the point of Schrödinger’s cat was to illustrate that you can’t know a quantum state until you measure it. Basically just saying “probability exists.”

    That wasn’t Schrödinger’s point at all.

    Schrödinger was responding to people in Bohr and von Neumann’s camp who claim that particles described mathematically by a superposition of states literally have no real observables in the real world at all. It is not just that they are random or probabilistic, but people in the “anti-realist” camp argue that they effectively no longer even exist anymore when they are described mathematically by a superposition of states. This position is sometimes called value indefiniteness.

    Schrödinger was criticizing this position by pointing out that you cannot separate your beliefs about the microworld from the macroworld, because macroscopic objects like cats are also made up of particles and should follow the same rules. Hence, he puts forward a thought experiment whereby a cat would also be described mathematically in a superposition of states.

    If you think superposition of states means it no longer has real definite properties in the real world, then the cat wouldn’t have real define properties in the real world until you open the box. Schrödinger’s point was that this is such an obvious absurdity that we should reject value indefiniteness for individual particles as well.

    You say:

    The reason it’s a big deal is that this probability is a real property. One that is supposed to be only one of two states. But instead it isn’t really in a state at all until you measure it, and that’s weird.

    But that is exactly the point Schrödinger was criticizing, not supporting.

    Value indefiniteness / anti-realism ultimately amounts to solipsism because if particles lack real, definite, observable properties in the real world when you are not looking at them, other people are also made up of particles, so other people wouldn’t have real, definite, observable properties in the real world when you are not looking at them.

    He was trying to illustrate that this position reduces to an absurdity and so we should not believe in that position.

    The point is that instead of assuming it is in one state or the other, you can and often should think of both possibilities at once. This is what makes quantum computing useful.

    If you perform a polar decomposition on the quantum state, you are left with a probability vector and a phase vector. The probability vector is the same kind of probability vector you use in classical probabilistic computing. The update rule for it in quantum computing literally only differs by an additional term which is a non-linear term that depends upon the phase vector.

    The "advantage’ comes from the phase vector. For N qubits, there are 2^N phases. A system of 300 qubits would have 2^300 phases, which is far greater than the number of atoms in the observable universe. A single logic gate thus can manipulate far more states of the system at once because it can manipulate these phases, which the stochastic dynamics of the bits have a dependence upon the phases, and thus you can not only manipulate the phases to do calculations but, if you are clever, you can write the algorithm in such a way that the effect it has on the probability distribution allows you to read off the results from the probability distribution.

    The phase vector does not contain anything probabilistic, so it contains nothing that looks like the qubit being in two places at once. That is contained in the probability vector, but there is no good reason to interpret a probability distribution as the system being in two places at once in quantum mechanics than there is in classical mechanics. The advantage comes from the phases, and the state of the phases just can influence the stochastic perturbations of the bits, and thus can influence the probability distribution.

    So you simply apply operations that increase or decrease the chances of certain outcomes and repeat until the answer you want has an incredibly high probability and the rest are nearly zero. Then you measure your qubit, collapsing the wave function, with a high probability that collapse will give you the answer you wanted.

    Again, perform a polar decomposition on the quantum state, break it apart into the probability vector and a phase vector. Then, apply a Bayesian knowledge update using Bayes’ theorem to the probability vector, exactly the way you’d do it in classical probabilistic computing. Then, simply undo the polar decomposition, i.e. recompose it back into a single complex-valued vector in Cartesian form.

    What you find is that this is mathematically equivalent to the collapse of the wavefunction. The so-called “collapse of the wavefunction” is literally just a Bayesian knowledge update on the degree of freedom of the quantum state associated with the probability distribution of the bits.

    It’s less like “the cat is both alive and dead” and more that “the terms ‘alive’ and ‘dead’ do not apply to the cat till you open the box”

    Sure, but that position reduces to solipsism, because then you don’t exist with a definite value until I look at you, either. But clearly you are thinking definite thoughts when I’m not looking, right?



  • Einstein didn’t even get a nobel prize for special relativity because it was considered too radical at the time.

    He shouldn’t have gotten one for SR specifically anyways because Hendrik Lorentz had already developed a theory that was mathematically equivalent and presented a year prior to Einstein.

    The speed of light can be derived from Maxwell’s equations, which is weird to be able to derive a speed just by analyzing how electromagnetism works, because anyone in any reference frame would derive the same speed, which implies the existence of a universal speed. If the speed is universal, what it is universal relative to?

    Physicists prior to Einstein believed there might be a universal reference frame which defines absolute time and absolute space, these days called a preferred foliation. The Michelson-Morley experiment was an attempt to measure the existence of this preferred foliation because most theories of how it worked would render it detectable in principle, but found no evidence for it.

    Most physicists these days retell this experiment as having debunked the idea and led to its replacement with Einstein’s special relativity. But the truth is more complicated than that, because Lorentz found you could patch the idea by just assuming objects physically contract based on their motion relative to preferred foliation. Lorentz’s theory was presented in 1904, a year before Einstein, and was mathematically equivalent, so it makes all the same predictions, and so anything Einstein’s theory would predict, his theory would’ve also predicted.

    The reason Lorentz’s theory fell by the wayside is because, by being able to explain the results of the Michelson-Morley experiment which was meant to detect the preferred foliation, it meant it was no longer detectable, and so people liked Einstein’s theory more that threw out this undetectable aspect. But it would still be weird to give Einstein the Nobel prize for what is ultimately just a simplification of Lorentz’s theory. (Einstein also already received one for something he did deserve anyways.)

    But there are also good reasons these days to consider putting the preferred foliation back in and that Lorentz was right. The Friedmann solution to Einstein’s general relativity (the solution associated with the universe we actually live in) spontaneously gives rise to a preferred foliation which is actually empirically observable. You can measure your absolute motion relative to the universe by looking at the cosmic dipole in the cosmic background radiation. Since we know you can measure it now and have actually measured our absolute motion in the universe, the argument against Lorentz’s theory is much weaker.

    An even stronger argument, however, comes from quantum mechanics. A famous theorem by the physicist John Bell proves the impossibility of “local realism,” and in this case locality means locality in terms of special relativity, and realism means belief that particles have real states in the real physical world independently of you looking at them (called the ontic states) which explain what shows up on your measurement device when you try to measure them. Since many physicists are committed to the idea of special relativity, they conclude that Bell’s theorem must debunk realism, that objective reality does not exist independently of you looking at it, and devolve into bizarre quantum mysticism and weirdness.

    But you can equally interpret this to mean that special relativity is wrong and that the preferred foliation needs to put back in. The physicist Hrvoje Nikolic for example published a paper titled “Relativistic QFT from a Bohmian perspective: A proof of concept” showing that you can fit quantum mechanics to a realist theory that reproduces the predictions of relativistic quantum mechanics if you add back in a preferred foliation.


  • “Why” implies an underlying ontology. Maybe there is something underneath it but it’s as far as it goes down as far as we currently know. If we don’t at least tentatively accept that our current most fundamental theories are the fundamental ontology of nature, at least as far as we currently know, then we can never believe anything about nature at all, because it would be an infinite regress. Every time we discover a new theory we can ask “well why does it work like that?” and so it would be impossible to actually believe anything about nature.



  • I got interested in quantum computing as a way to combat quantum mysticism. Quantum mystics love to use quantum mechanics to justify their mystical claims, like quantum immortality, quantum consciousness, quantum healing, etc. Some mystics use quantum mechanics to “prove” things like we all live inside of a big “cosmic consciousness” and there is no objective reality, and they often reference papers published in the actual academic literature.

    These papers on quantum foundations are almost universally framed in terms of a quantum circuit, because this deals with quantum information science, giving you a logical argument as to something “weird” about quantum mechanic’s logical structure, as shown in things like Bell’s theorem, the Frauchiger-Renner paradox, the Elitzur-Vaidman paradox, etc.

    If a person claims something mystical and sends you a paper, and you can’t understand the paper, how are you supposed to respond? But you can use quantum computing as a tool to help you learn quantum information science so that you can eventually parse the paper, and then you can know how to rebut their mystical claims. But without actually studying the mathematics you will be at a loss.

    You have to put some effort into understanding the mathematics. If you just go vaguely off of what you see in YouTube videos then you’re not going to understand what is actually being talked about. You can go through for example IBM’s courses on the basics of quantum computing and read a textbook on quantum computing and it gives you the foundations in quantum information science needed to actually parse the logical arguments in these papers and what they are really trying to say.