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That's not really how MWI works. There isn't some fixed number of universes; actually, there aren't really distinct universes (or timelines) at all. Attempting

That's not really how MWI works. There isn't some fixed number of universes; actually, there aren't really distinct universes (or timelines) at all. Attempting to count them is about like trying to measure the length of a coastline; they blend together once you zoom far enough in. Running the quantum computer causes 'new timelines' to be created. Though so would ordinary atoms just sitting there; the tricky thing about quantum computers is making it so the split is temporary. So the quantum computer gets split into multiple versions of itself, does some computation in each, and merges the results. This isn't map-reduce; there's a strictly limited set of ways in which you can do the merger, all of which are weird from a classical perspective. You can argue for MWI based on this, because the computations that got merged still had to happen somewhere. It's incompatible with Copenhagen, more so the bigger and longer-lasting the computation gets. It's not, strictly speaking, incompatible with pilot wave theory; but pilot wave theory is MWI plus an additional declaration that "Here, you see this timeline here? That's the real one, all the others are fake. Yes, all the computation needed to instantiate them still happens, but they lack the attribute of being real." Though that makes PWT incompatible with computationalism, and hence with concepts such as mind-uploading. Which is a bullet you can choose to bite, of course...

munchler 2y ago
Thank you. This makes sense.
monero-xmr 2y ago
I’d prefer to say we just go back in time the moment it collapses. How can you disagree with me? No proof of anything and we can all contrive untestable solutions. No wait, it’s actually God who exists in the wave collapse, and His divine intervention does the computation.
- astrange 2y ago
  > I’d prefer to say we just go back in time the moment it collapses. How can you disagree with me? No proof of anything and we can all contrive untestable solutions. That's close to retrocausality which is a serious theory/interpretation of quantum mechanics.
  - monero-xmr 2y ago
    I'd like to see some serious attempts to prove any of these theories. If not, we can just wildly imagine all sorts of possibilities.
fidotron 2y ago
The easy comparison for devs is quantum computing is like git branching. The big question being the PR approval process.
- whimsicalism 2y ago
  no that's not a good comparison for MWI, it's more continuous
  - fidotron 2y ago
    That sounds like you having a narrow understanding of git - there is no way it is not continuous.
    - whimsicalism 2y ago
      git branches are not continuous
      - fidotron 2y ago
        You mean as opposed to discrete? (And not in the usual sense of continuous) There is nothing stopping you putting probability distributions in git and branching them.
        whimsicalism 2y ago
        i think we are just not connecting in what we are saying, nbd
        dartos 2y ago
        Git operates on commits (branches are really nicknames for specific commits with some extra features), which are discrete steps. That’s what’s stopping you from doing anything continuous in git.
- amelius 2y ago
  Maybe our consciousness also branches, and all branches are approved.
adastra22 2y ago
I don't think this is accurate. There is no classical computation happening here, and there is no reason you have to have "room" for the classical computation to happen. That seems to be assuming that the universe is a classical substrate and a classical algorithm has to be instantiated somewhere. Quantum computing isn't classical computing. It isn't a Turing machine. It is a fundamentally different kind of information processing device, making use of non-classical physical phenomena. I'm not a defender of Copenhagen, but the wave collapse interpretation has no difficulty explaining quantum computation. A quantum computer creates extremely large, complexly entangled wave functions that upon collapse result in states that can be interpreted as solutions to problems that were encoded in the sequence of operations that setup the entangled wave function. The Everett interpretation is easier to think about in my opinion, and I prefer thinking in terms of MWI when I try to make sense of these results. But it is not necessary. Computer science is the study of universal Turing machines and their application. But Turing machines are only “universal” in the sense that they can represent any statement of mathematical logic, and that can (we believe) be used to simulate anything we can dream up. But there are intrinsic performance limitations of Turing machines, studied by algorithmic theory, which are artifacts of the Turing machine itself, not physical limitations of the universe we live in. That searching an unordered list with a serial processor takes O(n) time, for example. Grover showed that there are non-Turing machine quantum processes that could be used to perform the same computation in O(sqrt(n)) time. That doesn't mean we need to go looking for "where did that computation actually happen". That doesn't even make sense.
- slowmovintarget 2y ago
  According to this ( https://arxiv.org/pdf/2302.10778 https://arxiv.org/pdf/2302.10778 ), there are no branches, just decoherence (minus the "collapse").
  - adastra22 2y ago
    A paper proposing a radically different formulation of quantum mechanics, with only a half dozen non-author-citations, so heavy with jargon that it's hard to figure out what the author is claiming. Sorry, my crank meter is dialed to 11 right now and I don't think this is worth spending further time on.
athrowaway3z 2y ago
[flagged]
3form 2y ago
Why does the computation have to "happen somewhere"? I understand the desire to push the boundary of the classical reasoning, but I don't think it's something to be taken as an axiom, and I haven't heard about any proof either.
feoren 2y ago
There's no reason to think the computation is "happening" anywhere but our universe, or even "happening" at all in any real sense. Light follows a geodesic. Atomic reactions tend to minimize energy. Rivers follow the most efficient path to the sea. Where does any of that computation "happen"? Why is it any stranger that an electron "knows how" to follow a gradient in an electric field than that a quantum computer "knows how" to perform a random circuit sampling?

munchler 2y ago

Thank you. This makes sense.

monero-xmr 2y ago

I’d prefer to say we just go back in time the moment it collapses. How can you disagree with me? No proof of anything and we can all contrive untestable solutions. No wait, it’s actually God who exists in the wave collapse, and His divine intervention does the computation.

astrange 2y ago
> I’d prefer to say we just go back in time the moment it collapses. How can you disagree with me? No proof of anything and we can all contrive untestable solutions. That's close to retrocausality which is a serious theory/interpretation of quantum mechanics.
- monero-xmr 2y ago
  I'd like to see some serious attempts to prove any of these theories. If not, we can just wildly imagine all sorts of possibilities.

fidotron 2y ago

The easy comparison for devs is quantum computing is like git branching. The big question being the PR approval process.

whimsicalism 2y ago
no that's not a good comparison for MWI, it's more continuous
- fidotron 2y ago
  That sounds like you having a narrow understanding of git - there is no way it is not continuous.
  - whimsicalism 2y ago
    git branches are not continuous
    - fidotron 2y ago
      You mean as opposed to discrete? (And not in the usual sense of continuous) There is nothing stopping you putting probability distributions in git and branching them.
      - whimsicalism 2y ago
        i think we are just not connecting in what we are saying, nbd
      - dartos 2y ago
        Git operates on commits (branches are really nicknames for specific commits with some extra features), which are discrete steps. That’s what’s stopping you from doing anything continuous in git.
amelius 2y ago
Maybe our consciousness also branches, and all branches are approved.

adastra22 2y ago

I don't think this is accurate. There is no classical computation happening here, and there is no reason you have to have "room" for the classical computation to happen. That seems to be assuming that the universe is a classical substrate and a classical algorithm has to be instantiated somewhere. Quantum computing isn't classical computing. It isn't a Turing machine. It is a fundamentally different kind of information processing device, making use of non-classical physical phenomena. I'm not a defender of Copenhagen, but the wave collapse interpretation has no difficulty explaining quantum computation. A quantum computer creates extremely large, complexly entangled wave functions that upon collapse result in states that can be interpreted as solutions to problems that were encoded in the sequence of operations that setup the entangled wave function. The Everett interpretation is easier to think about in my opinion, and I prefer thinking in terms of MWI when I try to make sense of these results. But it is not necessary. Computer science is the study of universal Turing machines and their application. But Turing machines are only “universal” in the sense that they can represent any statement of mathematical logic, and that can (we believe) be used to simulate anything we can dream up. But there are intrinsic performance limitations of Turing machines, studied by algorithmic theory, which are artifacts of the Turing machine itself, not physical limitations of the universe we live in. That searching an unordered list with a serial processor takes O(n) time, for example. Grover showed that there are non-Turing machine quantum processes that could be used to perform the same computation in O(sqrt(n)) time. That doesn't mean we need to go looking for "where did that computation actually happen". That doesn't even make sense.

slowmovintarget 2y ago
According to this ( https://arxiv.org/pdf/2302.10778 https://arxiv.org/pdf/2302.10778 ), there are no branches, just decoherence (minus the "collapse").
- adastra22 2y ago
  A paper proposing a radically different formulation of quantum mechanics, with only a half dozen non-author-citations, so heavy with jargon that it's hard to figure out what the author is claiming. Sorry, my crank meter is dialed to 11 right now and I don't think this is worth spending further time on.

athrowaway3z 2y ago

[flagged]

3form 2y ago

Why does the computation have to "happen somewhere"? I understand the desire to push the boundary of the classical reasoning, but I don't think it's something to be taken as an axiom, and I haven't heard about any proof either.

feoren 2y ago

There's no reason to think the computation is "happening" anywhere but our universe, or even "happening" at all in any real sense. Light follows a geodesic. Atomic reactions tend to minimize energy. Rivers follow the most efficient path to the sea. Where does any of that computation "happen"? Why is it any stranger that an electron "knows how" to follow a gradient in an electric field than that a quantum computer "knows how" to perform a random circuit sampling?