4 ms·

>It is more like you expect to be able to observe 2 bytes of position information and 2 bytes of momentum information but the underlying quantum state is define

>It is more like you expect to be able to observe 2 bytes of position information and 2 bytes of momentum information but the underlying quantum state is defined by 2 bytes in total. The full 4 bytes cannot fit inside 2 bytes. So the programmer who wrote the simulation program took a shortcut. "No one will ever look at reality at this granular of a level, we should be good." Figures. Seriously though, great explanation.

eigenket 6y ago
I apologise for replying with what is essentially a rant, but as far as we can tell simulating quantum mechanics is exponentially (in the precise, mathematical sense) harder than simulating classical mechanics. I find it very "triggering" when people use this metaphor of uncertainty as a programming shortcut, when my life (currently working on simulating quantum systems) would be substantially (exponentially) easier if reality was classical.
- deleted 6y ago
  [deleted]
- FeepingCreature 6y ago
  Interested layman, but this always kind of rubs me the wrong way. I consider it a universal warning sign when your physical theory postulates that reality works a certain way underneath, and then conspires to keep you from exploiting this way. Superluminal collapse, for instance, or closed timelike curves; it seems to my intuition that these are clearly flaws in the theory rather than properties of reality. In a sense, the sci-fi concept of the ansible, where quantum collapse effects are exploited for FTL signaling, is more plausible than the view where quantum systems collapse instantly, but cannot be exploited for FTL. If your theory requires FTL in the "backend" to operate, it shouldn't end up with FTL just happening to not be exploitable in the "frontend". So I expect that when we find the true ToE, it's not going to end up with traits where the data structure in principle allows a certain capability, but coincidentally doesn't give us access to it; all limitations of that theory would follow directly from its structure, so that illegal operations cannot even be expressed. So when we find a practical limitation to the exploitation of a physical theory, then this seems to me to require, barring very good theoretical reasons to the contrary, a genuine underlying property of the universe that justifies this limit. As such, it seems to me, purely from an intuitive view, that of those three claims: - reality is quantum - quantum mechanics requires exponential cost to simulate - quantum mechanics cannot be exploited for exponential computation One has to be false! If reality requires exponential cost to simulate, we shouldn't expect it to then turn around and hide that capability from us. God famously doesn't play dice with the universe; but I doubt he's playing Poker either. Personally, I suspect quantum mechanics is cheaper than is widely believed. Idk, am I missing something obvious?
  - simiones 6y ago
    > - quantum mechanics cannot be exploited for exponential computation As far as we know for now, [a variant of [0] ] this one is the wrong claim: we do have algorithms (Shor's, Grover's) that are faster on Quantum Computers than any known classical algorithm. Of course, we do not yet have any proof that a faster classical algorithm can't exist, so the possibility remains open that this claim remains true. BUT, if this claim turns out to be true, then it is extremely likely that either one or both of the other 2 claims will immediately turn out to be wrong. [0] I would note that the "exponential" part is somewhat of a red herring. If there is any kind of asymptotic speed-up that QCs fundamentally have over classical computers, even if it's just quadratic, then the larger point will remain valid. > In a sense, the sci-fi concept of the ansible, where quantum collapse effects are exploited for FTL signaling, is more plausible than the view where quantum systems collapse instantly, but cannot be exploited for FTL. This is also what rubs me the wrong way about entanglement, and seems a very tantalizing thread to pull at if one wanted a more fundamental theory. The other thread of course is the measurement problem.
    - eigenket 6y ago
      Your two threads seem to be essentially the same thread. The "weird stuff" in entanglement comes pretty directly from collapse as part of measurement. If you drop this and go to something like many worlds then things look a bit nicer, but then you have so solve the measurement problem in many worlds, which seems quite hard.
      - Koshkin 6y ago
        But collapse is fake news, as it were. A state can be called a “superposition” only relative to a particular set of basis states, which, in turn, depends on what observable we are talking about, and the “collapse” is simply yet another way a state can change.
        simiones 6y ago
        No, collapse or some alternative to it is a fundamental component of quantum mechanics. Without it, quantum mechanics makes wildly wrong predictions. The Schrodinger equation almost always predicts that a particle has some particular amplitude at many different locations. However, if you try to detect a particle, you will never find it at more than one location. Furthermore, once the particle is detected at one particular location, you need to update the Schrodinger equation to give it amplitude 1 at that location and 0 everywhere else - if you don't perform this nonlinear update and instead use the old wave-function, the predictions for further experiments will be completely off. Now, the physical interpretation of this collapse varies wildly between different interpretations of QM, but some variant of it is always required - otherwise, the observations simply do not match the math. We don't yet have any theory consistent with QM that can make predictions without applying the Born rule.
- DebtDeflation 6y ago
  I think we may be talking about different simulations. I'm talking about THE simulation.
  - simiones 6y ago
    I think the GP understood this, but their point was that it is a false assumption that introducing the uncertainty principle in a classical simulation would simplify the computation. That is, if we think that the universe is a simulation running on a classical computer, then quantum effects such as the uncertainty principle CAN'T be a "shortcut" to make the simulation easier - as in fact they make the simulation literally exponentially harder. If we assume that the universe is a simulation running on a quantum computer, then quantum effects are fundamental anyway. Of course, everyone understands that this is a simple joke. Still, it's interesting that it goes completely against our intuitions as computer simulation designers.
treeman79 6y ago
https://m.youtube.com/watch?v=RlXdsyctD50&feature=emb_rel_pause https://m.youtube.com/watch?v=RlXdsyctD50&feature=emb_rel_pa... PBS Spacetkme has a great video on pilot wave. Getting rid of all the messy probability issues is amazing.

eigenket 6y ago

I apologise for replying with what is essentially a rant, but as far as we can tell simulating quantum mechanics is exponentially (in the precise, mathematical sense) harder than simulating classical mechanics. I find it very "triggering" when people use this metaphor of uncertainty as a programming shortcut, when my life (currently working on simulating quantum systems) would be substantially (exponentially) easier if reality was classical.

deleted 6y ago
[deleted]
FeepingCreature 6y ago
Interested layman, but this always kind of rubs me the wrong way. I consider it a universal warning sign when your physical theory postulates that reality works a certain way underneath, and then conspires to keep you from exploiting this way. Superluminal collapse, for instance, or closed timelike curves; it seems to my intuition that these are clearly flaws in the theory rather than properties of reality. In a sense, the sci-fi concept of the ansible, where quantum collapse effects are exploited for FTL signaling, is more plausible than the view where quantum systems collapse instantly, but cannot be exploited for FTL. If your theory requires FTL in the "backend" to operate, it shouldn't end up with FTL just happening to not be exploitable in the "frontend". So I expect that when we find the true ToE, it's not going to end up with traits where the data structure in principle allows a certain capability, but coincidentally doesn't give us access to it; all limitations of that theory would follow directly from its structure, so that illegal operations cannot even be expressed. So when we find a practical limitation to the exploitation of a physical theory, then this seems to me to require, barring very good theoretical reasons to the contrary, a genuine underlying property of the universe that justifies this limit. As such, it seems to me, purely from an intuitive view, that of those three claims: - reality is quantum - quantum mechanics requires exponential cost to simulate - quantum mechanics cannot be exploited for exponential computation One has to be false! If reality requires exponential cost to simulate, we shouldn't expect it to then turn around and hide that capability from us. God famously doesn't play dice with the universe; but I doubt he's playing Poker either. Personally, I suspect quantum mechanics is cheaper than is widely believed. Idk, am I missing something obvious?
- simiones 6y ago
  > - quantum mechanics cannot be exploited for exponential computation As far as we know for now, [a variant of [0] ] this one is the wrong claim: we do have algorithms (Shor's, Grover's) that are faster on Quantum Computers than any known classical algorithm. Of course, we do not yet have any proof that a faster classical algorithm can't exist, so the possibility remains open that this claim remains true. BUT, if this claim turns out to be true, then it is extremely likely that either one or both of the other 2 claims will immediately turn out to be wrong. [0] I would note that the "exponential" part is somewhat of a red herring. If there is any kind of asymptotic speed-up that QCs fundamentally have over classical computers, even if it's just quadratic, then the larger point will remain valid. > In a sense, the sci-fi concept of the ansible, where quantum collapse effects are exploited for FTL signaling, is more plausible than the view where quantum systems collapse instantly, but cannot be exploited for FTL. This is also what rubs me the wrong way about entanglement, and seems a very tantalizing thread to pull at if one wanted a more fundamental theory. The other thread of course is the measurement problem.
  - eigenket 6y ago
    Your two threads seem to be essentially the same thread. The "weird stuff" in entanglement comes pretty directly from collapse as part of measurement. If you drop this and go to something like many worlds then things look a bit nicer, but then you have so solve the measurement problem in many worlds, which seems quite hard.
    - Koshkin 6y ago
      But collapse is fake news, as it were. A state can be called a “superposition” only relative to a particular set of basis states, which, in turn, depends on what observable we are talking about, and the “collapse” is simply yet another way a state can change.
      - simiones 6y ago
        No, collapse or some alternative to it is a fundamental component of quantum mechanics. Without it, quantum mechanics makes wildly wrong predictions. The Schrodinger equation almost always predicts that a particle has some particular amplitude at many different locations. However, if you try to detect a particle, you will never find it at more than one location. Furthermore, once the particle is detected at one particular location, you need to update the Schrodinger equation to give it amplitude 1 at that location and 0 everywhere else - if you don't perform this nonlinear update and instead use the old wave-function, the predictions for further experiments will be completely off. Now, the physical interpretation of this collapse varies wildly between different interpretations of QM, but some variant of it is always required - otherwise, the observations simply do not match the math. We don't yet have any theory consistent with QM that can make predictions without applying the Born rule.
DebtDeflation 6y ago
I think we may be talking about different simulations. I'm talking about THE simulation.
- simiones 6y ago
  I think the GP understood this, but their point was that it is a false assumption that introducing the uncertainty principle in a classical simulation would simplify the computation. That is, if we think that the universe is a simulation running on a classical computer, then quantum effects such as the uncertainty principle CAN'T be a "shortcut" to make the simulation easier - as in fact they make the simulation literally exponentially harder. If we assume that the universe is a simulation running on a quantum computer, then quantum effects are fundamental anyway. Of course, everyone understands that this is a simple joke. Still, it's interesting that it goes completely against our intuitions as computer simulation designers.

treeman79 6y ago

https://m.youtube.com/watch?v=RlXdsyctD50&feature=emb_rel_pause https://m.youtube.com/watch?v=RlXdsyctD50&feature=emb_rel_pa... PBS Spacetkme has a great video on pilot wave. Getting rid of all the messy probability issues is amazing.