5 ms·

This is a really good explanation... but I can personally only square most of this entanglement non-locality with a many-worlds interpretation. Which is itself

This is a really good explanation... but I can personally only square most of this entanglement non-locality with a many-worlds interpretation. Which is itself hugely problematic.

gizmo686 11y ago
What is problematic about the many-worlds interpretation. Even without non-locality, it solves the non-determinism problem, which seems far more problematic to me.
- ploxiln 11y ago
  Well, the only one of the many-worlds that actually matters is this particular one, right here. What can we say/predict about this exact one. The others don't matter to me in the slightest... EDIT: well that's not a great explanation of why I dislike the many-worlds hypothesis, let me try again. Like some other ideas, including the existence of God, it's not (yet?) falsifiable. Which doesn't make it false, of course. But it's a really extraordinary idea. It's not just many worlds, it's a fuck-ton. And what can we do with all of them? Are they for nothing? Does nothing that happens matter because it happened differently in a separate but equally real "world"? I guess, I can believe that "god plays dice with the universe", but I can not believe that "god makes infinite copies of the whole universe and tries all possible quantum outcomes".
  - lisper 11y ago
    > it's a fuck-ton Or zero. (But it's definitely not one.) Personally I find the zero-worlds view to be the most intuitively satisfying: http://www.flownet.com/ron/QM.pdf http://www.flownet.com/ron/QM.pdf (Or the movie version: https://www.youtube.com/watch?v=dEaecUuEqfc https://www.youtube.com/watch?v=dEaecUuEqfc) David Mermin's Ithaca interpretation is essentially the same thing: http://arxiv.org/abs/quant-ph/9609013 http://arxiv.org/abs/quant-ph/9609013 The slogan is that "we are correlations without correlata".
  - gizmo686 11y ago
    The interpretation we use does not have any effect on our ability to make predictions; the equations are the same. EDIT: response to parent edit Almost by definition interpretations are not falsifiable. The many world interpenetration is literally equivalent to the other interpretations, because they all describe how we understand the meaning of the same mathematical model; and it is that model that is making predictions. In my opinion (as a mathematician, not a physicist), the many worlds interpretation is the more natural way to read quantum theory. That is to say, if I were tasked to design a universe given quantum physics as the specification, my naive implementation would correspond to the many worlds interpretation. An equally valid interpretation is that we are a computer simulation, and quantum physics describes the rounding behavior of said simulation. As far as I am concerned the only point of having an interpretation is to help build an intuition for the models.
  - lgas 11y ago
    Why not?
  - orangecat 11y ago
    But it's a really extraordinary idea. It's not just many worlds, it's a fuck-ton. Another way of looking at it is that there's only one "world": the amplitude distribution over quantum configuration space. https://www.quora.com/How-does-observation-collapse-probabilities https://www.quora.com/How-does-observation-collapse-probabil... has a decent explanation/argument.
  - sciolizer 11y ago
    Do you believe god exists and has a psychology? I'm trying to understand if you have trouble believing because you don't think god would create such a universe, or if you have trouble believing because such a universe is innately unbelievable. If the latter, then I would ask, "Do you believe the ocean is deep, even though you can only see the surface?"
    - ploxiln 11y ago
      The latter. I don't really understand the ocean metaphor, since humans have seen below the surface, quite a distance with remote-controlled submersibles.
      - sciolizer 11y ago
        Perhaps a better analogy would be, do you believe that matter exists beyond the observable universe? Because of the expansion of the universe, it is theoretically possible for me to get in a space ship and travel away from you at such a high speed that we would never be able to meet again, even if at some point we both decided to head back toward each other as fast as possible, and even if we were both immortal. Our light cones would no longer intersect. Probably you would assume that I continue to exist, despite that for all intents and purposes I cannot affect your life in anyway and therefore "don't" exist. Similarly if I crossed the event horizon of a black hole. I believe that a qubit is in superposition (i.e. exists in multiple miniature "universes"), because that theory produces results that are consistent with experiment. When the qubit's universes de-cohere with mine, such that for all intents and purposes I can now only ever observe the qubit in one particular state, why should I assume that the other universes have ceased to exist? Decoherence is a continuous process, just like traveling outside of a light cone, so why treat them any differently. It's rather arbitrary to say that increased distance in space preserves existence, while increased distance in phase space does not.
  - Kutta 11y ago
    A usual reply is that physicists don't or shouldn't care about metrics of the size of the universe but rather the simplicity and symmetry of physics. After all, the universe might well be infinite without many worlds, and why do even we care about amounts of stuff? The library of Babel doesn't contain more information than any single book in it. Similarly, pointing to specific areas in a large universe may require adding details.
  - fizx 11y ago
    > "god makes infinite copies of the whole universe and tries all possible quantum outcomes". MWI says that probability is conserved across the multiverse (unitarity of the global wavefunction)! The only reason we can "create universes" is because we're in the low-entropy time near the Big Bang. As we start getting closer to the heat death of the multiverse, then less "universes" are being created, because there's no room for them. In fact, given enough time, eventually some of the "universes" will actually join back together! If the multiverse is finite and closed (we don't know this), then sooner or later (like e^2^120 years later, according to a back-of-envelope calculation I saw) all of the universes will be lucky enough to join back up (Poincare recurrence), and we'll end up where we started. I like looking at MWI not as the creation of universes, but as the creation of perspectives on one universe. In any case, it obeys conservation laws.
- ryandamm 11y ago
  Well, for starters it requires an infinite number of universes, each with zero 'weight.' Secondly, it causes problems for materialist views of the universe. (I wrote a long term paper about this as an undergrad, but that was, like, 15 years ago and I don't have the cuneiform tablets anymore.) Briefly, there's no way to explain the statistical correlations between spin polarization states: if we measure the polarization of a photon in a basis that's only, say, 5 degrees offset from its known polarization, the statistical breakdown between the two resulting polarization states is something like 9:1; what if it's only a few arc-seconds off? Then the universe must divide more and more finely. You quickly realize the universe must be infinitely-divisible (because quantum collapse occurs so often, and each collapse anywhere in the universe must divide the universe, it can't even be discretized at, say, some Planck-like scale). That said, it does neatly solve local realism. But you have to believe in an immortal soul or something non-material -- I believe that has to be the 'weighting factor'. (Again, that was the uncomfortable conclusion of my paper, wish I could conjure more of it.)
  - norea-armozel 11y ago
    I think that materialism is a dead concept anyways. It just doesn't seem to support itself under the weight of evidence in physics which seems to contradict it. So, either materialism goes or physicists are going to have a fun time with new experiments overturning old ones.
    - ryandamm 11y ago
      Wow, that's a strong statement. (Are we using the same definition of materialism?) I use it to mean that there are no outside forces describing the state of the universe beyond what's materially measurable/describable; in other words, probably we have no transmaterial soul. That's a strong assumption for anyone who's religious, but it's sort of gospel for atheists. That said, it's the many-worlds hypothesis doesn't square with a totally-naive interpretation of Bell's Inequality and materialism/atheism. So... are you saying that we have to admit there's a God/transmaterial soul / some other magical thing because we don't understand the implication of Bell's inequality? If so, that's a big jump, but I can't say it's wrong. Just that I don't take that leap along with you. You know, there are more things in heaven and earth, Horatio, than etc etc. For both of us.
mikekchar 11y ago
I have no idea if this makes sense, as it is mostly random typing from a monkey (who has been drinking beer, no less)... but couldn't it be perfectly reasonable if non-locality was the result of something that is non-observable? I mean, if I flip a coin and heads comes up, it's not surprising that tails is down. The head is connected to the tail, so I can't have both coming up at the same time. Imagine that there are inhabitants of a torus world with the coin at one point. It's spinning there. Alice stays to watch the spinning coin and Bob wanders along the torus in the opposite direction. Eventually he sees a spinning coin too. It can't be the same coin, because he's walked a long way in the opposite direction. So he watches the coin. Eventually it stops spinning. Alice sees heads and Bob sees tails. No matter how often they do this, it works out opposite. It's not that one side of the coin is communicating to the other side of the coin at the other "end" of the torus. It's just that there is no other way for it to work out. I'm not suggesting that it actually works this way, I'm just giveng my drunken monkey interpretation of how particles could exhibit this behaviour without many worlds ;-)
- Manishearth 11y ago
  I'm not sure what you're trying to say, but it appears that you're conjecturing that "everything is local". That doesn't square too well with relativity, though. Either that or you're talking of a hidden variable theory, which is exactly what Bell's theorem disallows.
- ryandamm 11y ago
  Beer is a good tool to try to understand quantum mechanics, but there's stronger stuff that might be more helpful. That said, you're articulating a version of what's called a 'hidden variable' view of QM, which is actually explicitly what Bell's inequality is meant to disprove. I'm going to write a long post at root to try to explain this more, because I think it's really important to talk in particulars when discussing QM... hopefully it helps.
  - mikekchar 11y ago
    I'd really appreciate that. I've been looking at Wikipedia articles and I really can't quite understand what "local hidden variable" means in relation to "non-local hidden variable". I wasn't really suggesting that the system was deterministic. The coin is neither heads nor tails until someone looks at it. I was suggesting that it is the same coin in 2 different places (from the vantage point of the people observing it). However, you can't know a priori that it is the same coin. You have to observe it in both places and communicate your discovery. Since you are trapped in your torus, it will take time communicate it. But it's not like the coin is sending messages to itself to say, "if someone looks at the other side, make sure it is tails". It just is. Similarly, it is not in a determined state at the point of entaglement. It is only determined when one party looks at it. But then that decides what the other party will see. I honestly don't see how you would create a test for this because you would not be able to determine if 2 particles were entanlged (the same coin in my silly example) without observing them. Anyway, I appreciate your patience. I am keenly aware that "crazy theories from people who have no idea what they are talking about" are not particularly helpful. But if you write a blog post on the topic, that's the kind of area I'd like to see explained better ;-)

This is a really good explanation... but I can personally only square most of this entanglement non-locality with a many-worlds interpretation. Which is itself hugely problematic.

gizmo686 11y ago

What is problematic about the many-worlds interpretation. Even without non-locality, it solves the non-determinism problem, which seems far more problematic to me.

ploxiln 11y ago
Well, the only one of the many-worlds that actually matters is this particular one, right here. What can we say/predict about this exact one. The others don't matter to me in the slightest... EDIT: well that's not a great explanation of why I dislike the many-worlds hypothesis, let me try again. Like some other ideas, including the existence of God, it's not (yet?) falsifiable. Which doesn't make it false, of course. But it's a really extraordinary idea. It's not just many worlds, it's a fuck-ton. And what can we do with all of them? Are they for nothing? Does nothing that happens matter because it happened differently in a separate but equally real "world"? I guess, I can believe that "god plays dice with the universe", but I can not believe that "god makes infinite copies of the whole universe and tries all possible quantum outcomes".
- lisper 11y ago
  > it's a fuck-ton Or zero. (But it's definitely not one.) Personally I find the zero-worlds view to be the most intuitively satisfying: http://www.flownet.com/ron/QM.pdf http://www.flownet.com/ron/QM.pdf (Or the movie version: https://www.youtube.com/watch?v=dEaecUuEqfc https://www.youtube.com/watch?v=dEaecUuEqfc) David Mermin's Ithaca interpretation is essentially the same thing: http://arxiv.org/abs/quant-ph/9609013 http://arxiv.org/abs/quant-ph/9609013 The slogan is that "we are correlations without correlata".
- gizmo686 11y ago
  The interpretation we use does not have any effect on our ability to make predictions; the equations are the same. EDIT: response to parent edit Almost by definition interpretations are not falsifiable. The many world interpenetration is literally equivalent to the other interpretations, because they all describe how we understand the meaning of the same mathematical model; and it is that model that is making predictions. In my opinion (as a mathematician, not a physicist), the many worlds interpretation is the more natural way to read quantum theory. That is to say, if I were tasked to design a universe given quantum physics as the specification, my naive implementation would correspond to the many worlds interpretation. An equally valid interpretation is that we are a computer simulation, and quantum physics describes the rounding behavior of said simulation. As far as I am concerned the only point of having an interpretation is to help build an intuition for the models.
- lgas 11y ago
  Why not?
- orangecat 11y ago
  But it's a really extraordinary idea. It's not just many worlds, it's a fuck-ton. Another way of looking at it is that there's only one "world": the amplitude distribution over quantum configuration space. https://www.quora.com/How-does-observation-collapse-probabilities https://www.quora.com/How-does-observation-collapse-probabil... has a decent explanation/argument.
- sciolizer 11y ago
  Do you believe god exists and has a psychology? I'm trying to understand if you have trouble believing because you don't think god would create such a universe, or if you have trouble believing because such a universe is innately unbelievable. If the latter, then I would ask, "Do you believe the ocean is deep, even though you can only see the surface?"
  - ploxiln 11y ago
    The latter. I don't really understand the ocean metaphor, since humans have seen below the surface, quite a distance with remote-controlled submersibles.
    - sciolizer 11y ago
      Perhaps a better analogy would be, do you believe that matter exists beyond the observable universe? Because of the expansion of the universe, it is theoretically possible for me to get in a space ship and travel away from you at such a high speed that we would never be able to meet again, even if at some point we both decided to head back toward each other as fast as possible, and even if we were both immortal. Our light cones would no longer intersect. Probably you would assume that I continue to exist, despite that for all intents and purposes I cannot affect your life in anyway and therefore "don't" exist. Similarly if I crossed the event horizon of a black hole. I believe that a qubit is in superposition (i.e. exists in multiple miniature "universes"), because that theory produces results that are consistent with experiment. When the qubit's universes de-cohere with mine, such that for all intents and purposes I can now only ever observe the qubit in one particular state, why should I assume that the other universes have ceased to exist? Decoherence is a continuous process, just like traveling outside of a light cone, so why treat them any differently. It's rather arbitrary to say that increased distance in space preserves existence, while increased distance in phase space does not.
- Kutta 11y ago
  A usual reply is that physicists don't or shouldn't care about metrics of the size of the universe but rather the simplicity and symmetry of physics. After all, the universe might well be infinite without many worlds, and why do even we care about amounts of stuff? The library of Babel doesn't contain more information than any single book in it. Similarly, pointing to specific areas in a large universe may require adding details.
- fizx 11y ago
  > "god makes infinite copies of the whole universe and tries all possible quantum outcomes". MWI says that probability is conserved across the multiverse (unitarity of the global wavefunction)! The only reason we can "create universes" is because we're in the low-entropy time near the Big Bang. As we start getting closer to the heat death of the multiverse, then less "universes" are being created, because there's no room for them. In fact, given enough time, eventually some of the "universes" will actually join back together! If the multiverse is finite and closed (we don't know this), then sooner or later (like e^2^120 years later, according to a back-of-envelope calculation I saw) all of the universes will be lucky enough to join back up (Poincare recurrence), and we'll end up where we started. I like looking at MWI not as the creation of universes, but as the creation of perspectives on one universe. In any case, it obeys conservation laws.
ryandamm 11y ago
Well, for starters it requires an infinite number of universes, each with zero 'weight.' Secondly, it causes problems for materialist views of the universe. (I wrote a long term paper about this as an undergrad, but that was, like, 15 years ago and I don't have the cuneiform tablets anymore.) Briefly, there's no way to explain the statistical correlations between spin polarization states: if we measure the polarization of a photon in a basis that's only, say, 5 degrees offset from its known polarization, the statistical breakdown between the two resulting polarization states is something like 9:1; what if it's only a few arc-seconds off? Then the universe must divide more and more finely. You quickly realize the universe must be infinitely-divisible (because quantum collapse occurs so often, and each collapse anywhere in the universe must divide the universe, it can't even be discretized at, say, some Planck-like scale). That said, it does neatly solve local realism. But you have to believe in an immortal soul or something non-material -- I believe that has to be the 'weighting factor'. (Again, that was the uncomfortable conclusion of my paper, wish I could conjure more of it.)
- norea-armozel 11y ago
  I think that materialism is a dead concept anyways. It just doesn't seem to support itself under the weight of evidence in physics which seems to contradict it. So, either materialism goes or physicists are going to have a fun time with new experiments overturning old ones.
  - ryandamm 11y ago
    Wow, that's a strong statement. (Are we using the same definition of materialism?) I use it to mean that there are no outside forces describing the state of the universe beyond what's materially measurable/describable; in other words, probably we have no transmaterial soul. That's a strong assumption for anyone who's religious, but it's sort of gospel for atheists. That said, it's the many-worlds hypothesis doesn't square with a totally-naive interpretation of Bell's Inequality and materialism/atheism. So... are you saying that we have to admit there's a God/transmaterial soul / some other magical thing because we don't understand the implication of Bell's inequality? If so, that's a big jump, but I can't say it's wrong. Just that I don't take that leap along with you. You know, there are more things in heaven and earth, Horatio, than etc etc. For both of us.

mikekchar 11y ago

I have no idea if this makes sense, as it is mostly random typing from a monkey (who has been drinking beer, no less)... but couldn't it be perfectly reasonable if non-locality was the result of something that is non-observable? I mean, if I flip a coin and heads comes up, it's not surprising that tails is down. The head is connected to the tail, so I can't have both coming up at the same time. Imagine that there are inhabitants of a torus world with the coin at one point. It's spinning there. Alice stays to watch the spinning coin and Bob wanders along the torus in the opposite direction. Eventually he sees a spinning coin too. It can't be the same coin, because he's walked a long way in the opposite direction. So he watches the coin. Eventually it stops spinning. Alice sees heads and Bob sees tails. No matter how often they do this, it works out opposite. It's not that one side of the coin is communicating to the other side of the coin at the other "end" of the torus. It's just that there is no other way for it to work out. I'm not suggesting that it actually works this way, I'm just giveng my drunken monkey interpretation of how particles could exhibit this behaviour without many worlds ;-)

Manishearth 11y ago
I'm not sure what you're trying to say, but it appears that you're conjecturing that "everything is local". That doesn't square too well with relativity, though. Either that or you're talking of a hidden variable theory, which is exactly what Bell's theorem disallows.
ryandamm 11y ago
Beer is a good tool to try to understand quantum mechanics, but there's stronger stuff that might be more helpful. That said, you're articulating a version of what's called a 'hidden variable' view of QM, which is actually explicitly what Bell's inequality is meant to disprove. I'm going to write a long post at root to try to explain this more, because I think it's really important to talk in particulars when discussing QM... hopefully it helps.
- mikekchar 11y ago
  I'd really appreciate that. I've been looking at Wikipedia articles and I really can't quite understand what "local hidden variable" means in relation to "non-local hidden variable". I wasn't really suggesting that the system was deterministic. The coin is neither heads nor tails until someone looks at it. I was suggesting that it is the same coin in 2 different places (from the vantage point of the people observing it). However, you can't know a priori that it is the same coin. You have to observe it in both places and communicate your discovery. Since you are trapped in your torus, it will take time communicate it. But it's not like the coin is sending messages to itself to say, "if someone looks at the other side, make sure it is tails". It just is. Similarly, it is not in a determined state at the point of entaglement. It is only determined when one party looks at it. But then that decides what the other party will see. I honestly don't see how you would create a test for this because you would not be able to determine if 2 particles were entanlged (the same coin in my silly example) without observing them. Anyway, I appreciate your patience. I am keenly aware that "crazy theories from people who have no idea what they are talking about" are not particularly helpful. But if you write a blog post on the topic, that's the kind of area I'd like to see explained better ;-)