4 ms·

Because that's what quantum mechanics in it's purest form tells us. Avoiding the many worlds requires tagging on extra stuff not in the equations.

tsimionescu 3y ago
Quantum mechanics tells us that, in order to predict the outcome of a measurement, we have to compute a specific probability based on the amplitude of the wavefunction. We can explain this probability as some kind of collapse, or we can explain it as some measure of the number of observers making the measurement in parallel "worlds". Neither is inherently closer to the math.
- consilient 3y ago
  > Quantum mechanics tells us that, in order to predict the outcome of a measurement, we have to compute a specific probability based on the amplitude of the wavefunction Even this is already wading into interpretational waters. The math says nothing about whether a given POVM should be thought of as a measurement or an interaction (or both, or neither).
  - tsimionescu 3y ago
    Sure, it's not part of the math, but it is part of the physics. There is a very clear distinction in the theory between "interactions", governed entirely by the Schrodinger equation (or its relativistic versions, or QFT), and a "measurement", where you have the apply the Born rule not only to predict what the measurement device will show, but also to correctly predict what will happen in a subsequent experiment on the same particle. Without the Born rule, QM makes nonsensical predictions that don't explain what happens. Decoherence helps explain certain things directly from the math without appealing to the extra Born rule, but not fully, and not quantitatively (not the specific probabilities).
    - bowsamic 3y ago
      > Sure, it's not part of the math, but it is part of the physics. "the physics" here is a specific interpretation > Decoherence helps explain certain things directly from the math without appealing to the extra Born rule, but not fully, and not quantitatively (not the specific probabilities). You can derive the Born rule using decoherence
      - tsimionescu 3y ago
        > "the physics" here is a specific interpretation No, "the physics" here is the way we are supposed to tie the math to physical observations. You can't explain all of our experiments if you don't make a distinction between interactions which preserve quantum properties and measurements which lead to classical observations. For a specific example, you can't explain the double-slit experiment with a detector at one slit if you don't make this distinction. > You can derive the Born rule using decoherence No, you can't. I have actively looked for such derivations and found none (at least none that are considered credible), and there is literature that explicitly says that this hasn't been convincingly done, e.g. [0]: > My main conclusion is that there is no way to derive the Born rule without additional assumptions. It is true both in the framework of collapse theories and, more surprisingly, in the framework of the MWI. The main open question is not the validity of various proofs, but what are the most natural assumptions we should add for proving the Born rule. [0] https://pages.jh.edu/rrynasi1/HealeySeminar/literature/Vaidman2020DerivationsOfTheBornRule.pdf https://pages.jh.edu/rrynasi1/HealeySeminar/literature/Vaidm...
        bowsamic 3y ago
        > the way we are supposed to tie the math to physical observations Again, that's a matter of interpretation. The different quantum interpretations say different things here. > No, you can't. Yes, you can. Look up Quantum Darwinism. PS. throwing "nuh uhs" back to a professional in the field is not appropriate. Get your respect in order.
        tsimionescu 3y ago
- edgyquant 3y ago
  Why should we not just take it as a probability based abstraction for something we don’t have a true understanding of and move on? Anything else seems like weird theology to me.
  - meroes 3y ago
    1) Because physics has had an ontology, what there really is, since like Aristotle. Even if ontology changes, posing one has worked for roughly 2500 years to partially guide science. It really does inform all kinds of experiments, even thought experiments. BUT, you might be right the trade off you propose is more worth it 2) Reichenbach's principle says any correlation must have a cause. Even without an idea of an ontology like in 1) this looser principle is hard to give up as well. It explains the mystery behind Simpson's for example. And why without the causal model behind correlations, you could easily take the wrong drug for you specifically. Again though, these are guiding principles and trade offs I am curious to see how we could progress without them
    - edgyquant 3y ago
      I really think it’s best to leave such metaphysical speculation out of it (or rather leave that to metaphysics.) Sure it could be right, and reality is definitely weird as hell, but it just seems like theology to me when you start pushing such things as fact when nothing says it is. Don’t get me wrong I have weird beliefs about the universe too but I would always stress they’re my weird beliefs and not something we’ve proved. The many worlds interpretation is pretty mainstream at this point and it leads the masses to believe it’s either true or that scientists are batshit crazy. Not a good look imo.
  - urinotherapist 3y ago
    [flagged]
  - tsimionescu 3y ago
    Sure, it's perfectly valid to say we don't understand it - but the ambition of physics is to actually understand things like that. So if we agree that it is something that we don't know yet, then it remains a target for new theory development or new experiments. Physics is ultimately not about predicting the outcomes of experiments. It goes farther than that: it is about coming up with a model of the world that humans can understand. The experiments and predictions are just there to validate that the model actually corresponds to the world, but they are not an end in itself. And all of this speculation about what the Born postulate actually means has in fact lead to new experiments and new theories. If we had only ignored it, we probably wouldn't have discovered Bell's theorem, and we probably wouldn't have discovered decoherence.
TheOtherHobbes 3y ago
As opposed to tagging on a literally incalculable number of extra universes for every possible quantum interaction.

tsimionescu 3y ago

Quantum mechanics tells us that, in order to predict the outcome of a measurement, we have to compute a specific probability based on the amplitude of the wavefunction. We can explain this probability as some kind of collapse, or we can explain it as some measure of the number of observers making the measurement in parallel "worlds". Neither is inherently closer to the math.

consilient 3y ago
> Quantum mechanics tells us that, in order to predict the outcome of a measurement, we have to compute a specific probability based on the amplitude of the wavefunction Even this is already wading into interpretational waters. The math says nothing about whether a given POVM should be thought of as a measurement or an interaction (or both, or neither).
- tsimionescu 3y ago
  Sure, it's not part of the math, but it is part of the physics. There is a very clear distinction in the theory between "interactions", governed entirely by the Schrodinger equation (or its relativistic versions, or QFT), and a "measurement", where you have the apply the Born rule not only to predict what the measurement device will show, but also to correctly predict what will happen in a subsequent experiment on the same particle. Without the Born rule, QM makes nonsensical predictions that don't explain what happens. Decoherence helps explain certain things directly from the math without appealing to the extra Born rule, but not fully, and not quantitatively (not the specific probabilities).
  - bowsamic 3y ago
    > Sure, it's not part of the math, but it is part of the physics. "the physics" here is a specific interpretation > Decoherence helps explain certain things directly from the math without appealing to the extra Born rule, but not fully, and not quantitatively (not the specific probabilities). You can derive the Born rule using decoherence
    - tsimionescu 3y ago
      > "the physics" here is a specific interpretation No, "the physics" here is the way we are supposed to tie the math to physical observations. You can't explain all of our experiments if you don't make a distinction between interactions which preserve quantum properties and measurements which lead to classical observations. For a specific example, you can't explain the double-slit experiment with a detector at one slit if you don't make this distinction. > You can derive the Born rule using decoherence No, you can't. I have actively looked for such derivations and found none (at least none that are considered credible), and there is literature that explicitly says that this hasn't been convincingly done, e.g. [0]: > My main conclusion is that there is no way to derive the Born rule without additional assumptions. It is true both in the framework of collapse theories and, more surprisingly, in the framework of the MWI. The main open question is not the validity of various proofs, but what are the most natural assumptions we should add for proving the Born rule. [0] https://pages.jh.edu/rrynasi1/HealeySeminar/literature/Vaidman2020DerivationsOfTheBornRule.pdf https://pages.jh.edu/rrynasi1/HealeySeminar/literature/Vaidm...
      - bowsamic 3y ago
        > the way we are supposed to tie the math to physical observations Again, that's a matter of interpretation. The different quantum interpretations say different things here. > No, you can't. Yes, you can. Look up Quantum Darwinism. PS. throwing "nuh uhs" back to a professional in the field is not appropriate. Get your respect in order.
        tsimionescu 3y ago
edgyquant 3y ago
Why should we not just take it as a probability based abstraction for something we don’t have a true understanding of and move on? Anything else seems like weird theology to me.
- meroes 3y ago
  1) Because physics has had an ontology, what there really is, since like Aristotle. Even if ontology changes, posing one has worked for roughly 2500 years to partially guide science. It really does inform all kinds of experiments, even thought experiments. BUT, you might be right the trade off you propose is more worth it 2) Reichenbach's principle says any correlation must have a cause. Even without an idea of an ontology like in 1) this looser principle is hard to give up as well. It explains the mystery behind Simpson's for example. And why without the causal model behind correlations, you could easily take the wrong drug for you specifically. Again though, these are guiding principles and trade offs I am curious to see how we could progress without them
  - edgyquant 3y ago
    I really think it’s best to leave such metaphysical speculation out of it (or rather leave that to metaphysics.) Sure it could be right, and reality is definitely weird as hell, but it just seems like theology to me when you start pushing such things as fact when nothing says it is. Don’t get me wrong I have weird beliefs about the universe too but I would always stress they’re my weird beliefs and not something we’ve proved. The many worlds interpretation is pretty mainstream at this point and it leads the masses to believe it’s either true or that scientists are batshit crazy. Not a good look imo.
- urinotherapist 3y ago
  [flagged]
- tsimionescu 3y ago
  Sure, it's perfectly valid to say we don't understand it - but the ambition of physics is to actually understand things like that. So if we agree that it is something that we don't know yet, then it remains a target for new theory development or new experiments. Physics is ultimately not about predicting the outcomes of experiments. It goes farther than that: it is about coming up with a model of the world that humans can understand. The experiments and predictions are just there to validate that the model actually corresponds to the world, but they are not an end in itself. And all of this speculation about what the Born postulate actually means has in fact lead to new experiments and new theories. If we had only ignored it, we probably wouldn't have discovered Bell's theorem, and we probably wouldn't have discovered decoherence.

TheOtherHobbes 3y ago

As opposed to tagging on a literally incalculable number of extra universes for every possible quantum interaction.