8 ms·

This article completely ignored the Many Worlds Interpretation, which preserves all of realism, locality, and Relativity.

MBlume 14y ago
Yeah. It shouldn't be that surprising that when you arbitrarily assume that part of the wavefunction magically disappears sometimes, you get weird results like non-locality.
- Osmium 14y ago
  Could you expand on this a little more? I'm not quite sure I follow.
  - Symmetry 14y ago
    Lets say you have some experiment which gives you a 1 or a 0, and you have two entangled particles which will give the same result depsite the result being random and the measurements being taken outside each other's lightcones. In Collapse QM there was some instantanious communication making that possible. In Many Worlds you'd find that for each measurement the wavefunction split into two branches, one corresponding to 1 and one to 0, in each location. From the sites of both measurements the decoherence spreads outwards as particle interactions happen, and when they finally touch the two 1 segments and the two 0 segments merge, and there is one area split along 1/0 in the wave function instead of two. That's all horribly simplified, but should get the idea across.
  - btilly 14y ago
    The many world's interpretation is based on the assumption that both the observed system and the observer is modeled by a wavefunction. In that case observation is entanglement, which seems weird to us, but which makes perfect logical sense. Other interpretations of quantum mechanics start with the assumption that the world is fundamentally like our naive experience leads us to think of it as. Therefore when we observe something, we couldn't really be thrown into a superposition of states, each of which observed a different thing and which cannot meaningfully interact due to quantum mechanical principles. If we can't be thrown into such a superposition, then there must be some sort of underlying reality, or quantum collapse, or other weirdness that is not explained by QM. All of the weirdness of interpretations other than many worlds can be understood as the conflict between how they would like to understand the world (there is a reality that happened), and how quantum mechanics described things. All of the weirdness of the many worlds interpretation can be understood as, "We can't perceive the process of quantum superposition, so it seems really, really weird to us."
- IvoDankolov 14y ago
  It's always amusing to see the kind of excuses that pop up when you try to explain entanglement or interference in the mindset of wavefunction collapse. I'm still not entirely sure why so many people consider collapse to be simpler. Is it too daunting to think of the world as an amplitude distribution that propagates in a way that we're not intuitively used to? Too hard to think of ourselves as part of quantum mechanics, because that thing I see there on the measuring device must be the reality, damn it, and what the hell do you mean I've just entangled myself and the device along with the system? Or maybe just tradition and accepting the "scripture" coming from the established authority. How could we best test that?
- kinghajj 14y ago
  The Bohm interpretation has a universal wavefunction and non-locality, though.
Ingaz 14y ago
Correct if I'm wrong, but I think that Many Worlds Interpetation does not explain a thing. It's like religion - one can think it's possible, other - impossible. But it can't be proved or disproved
- nessus42 14y ago
  I'm pretty sure that, in theory, all the major interpretations of QM are experimentally distinguishable from each other. The feasibility of ever being able to perform some of these experiments, however, is rather questionable. Two exceptions to this are (1) that the Many Worlds Interpretation is experimentally indistinguishable from the Bohm Interpretation, unless you want to commit suicide many times with a quantum revolver; and (2) the Copenhagen Interpretation doesn't define what a "measurement" is, so scientifically determining whether it's correct or not is impossible. None of this implies that any of this is "like religion".
  - pfedor 14y ago
    Be specific. What experiment do you have in mind that could distinguish between interpretations? Note that if the "experiment" involves dying to see what's on the other side then it doesn't exactly make it seem less like a religion.
    - nessus42 14y ago
      You might as well say that the Bohm interpretation is "like religion" then, rather than saying that the MWI is. If your assertion is that we might never know which is true, the Many Worlds Interpretation or the Bohm Interpretation, then you might be right. But, if it comes down to these two, most scientists are going to go with the Many Worlds Interpretation by Occam's razor. There are many other theories that we reject by Occam's razor that we can't disprove, and yet we don't typically consider these rejections to be a matter of "religion".
      - pfedor 14y ago
        You might as well say that the Bohm interpretation is "like religion" then, rather than saying that the MWI is. I might except MWI clearly has more True Believers. If your assertion is that we might never know which is true My assertion is that since all interpretations lead to the same exact predictions for every imaginable experiment, it doesn't make sense to say that in any meaningful way one interpretation is true and the others aren't. You might as well be arguing whether the electromagnetic field is weaved by tiny angels out of their hair or not. The Copenhagen interpretation is the closest to "no interpretation" in that it's the most direct way of translating the math into actual predictions. Quoting the guy who said you shouldn't multiply entities without necessity, to justify the introduction of infinitely many parallel worlds, is an interesting rhetorical maneuver.
kybernetikos 14y ago
Can you explain how MWI is local? In the period of time before the observer is 'entangled' into the same system as the observed particles, the different possibilities can interfere with each other. If this can happen even if the entangled particles are separated by a lot of space, surely that is the same as nonlocality. Maybe my confusion is that I'm not sure a which point the universe splits. Suppose I entangle two particles, then separate them by a large amount, my universe hasn't split yet, because before I make the measurement, I haven't become entangled with the state of the particles, but when I do, surely the spreading entanglement of myself with the possibilities centers at both entangled particles (i.e. it is nonlocal)?
- kybernetikos 14y ago
  Let me try to explain myself better: Two particles are entangled and separated by a vast distance. At some point, I conduct a measurement on the first particle, causing me to split into two different versions of myself that have measured two different states. Now, the effect of that measurement spreads outwards from the site of the measurement, so I may affect other things based on the measurement, etc. My problem is that if a measurement is done on the other particle, long before any message from me could possibly have got there, then that measurement and the effects it has on its local environment and the effects they have are all also dependent on my measurement. I imagine this as a wave of universe splitting spreading out from the site of my measurement and the entangled particle despite the separation. Now, perhaps this is a nontechnical use of the word nonlocal, but I'd describe that as a nonlocal phenomenon.
  - nessus42 14y ago
    > My problem is that if a measurement is done on the other particle, long before any message from me could possibly have got there, then that measurement and the effects it has on its local environment and the effects they have are all also dependent on my measurement. Imagine that your friend Joe writes the same word on two pieces of paper, puts them in envelopes and hands one envelope to you and mails the other envelope to Paris. At some point in time, you open up your envelope and read the word "popcorn". At some other point in time, Pierre open up his envelope and reads the same word. The word that Pierre reads is not "dependent on your measurement". Nothing nonlocal occurred.

MBlume 14y ago

Yeah. It shouldn't be that surprising that when you arbitrarily assume that part of the wavefunction magically disappears sometimes, you get weird results like non-locality.

Osmium 14y ago
Could you expand on this a little more? I'm not quite sure I follow.
- Symmetry 14y ago
  Lets say you have some experiment which gives you a 1 or a 0, and you have two entangled particles which will give the same result depsite the result being random and the measurements being taken outside each other's lightcones. In Collapse QM there was some instantanious communication making that possible. In Many Worlds you'd find that for each measurement the wavefunction split into two branches, one corresponding to 1 and one to 0, in each location. From the sites of both measurements the decoherence spreads outwards as particle interactions happen, and when they finally touch the two 1 segments and the two 0 segments merge, and there is one area split along 1/0 in the wave function instead of two. That's all horribly simplified, but should get the idea across.
- btilly 14y ago
  The many world's interpretation is based on the assumption that both the observed system and the observer is modeled by a wavefunction. In that case observation is entanglement, which seems weird to us, but which makes perfect logical sense. Other interpretations of quantum mechanics start with the assumption that the world is fundamentally like our naive experience leads us to think of it as. Therefore when we observe something, we couldn't really be thrown into a superposition of states, each of which observed a different thing and which cannot meaningfully interact due to quantum mechanical principles. If we can't be thrown into such a superposition, then there must be some sort of underlying reality, or quantum collapse, or other weirdness that is not explained by QM. All of the weirdness of interpretations other than many worlds can be understood as the conflict between how they would like to understand the world (there is a reality that happened), and how quantum mechanics described things. All of the weirdness of the many worlds interpretation can be understood as, "We can't perceive the process of quantum superposition, so it seems really, really weird to us."
IvoDankolov 14y ago
It's always amusing to see the kind of excuses that pop up when you try to explain entanglement or interference in the mindset of wavefunction collapse. I'm still not entirely sure why so many people consider collapse to be simpler. Is it too daunting to think of the world as an amplitude distribution that propagates in a way that we're not intuitively used to? Too hard to think of ourselves as part of quantum mechanics, because that thing I see there on the measuring device must be the reality, damn it, and what the hell do you mean I've just entangled myself and the device along with the system? Or maybe just tradition and accepting the "scripture" coming from the established authority. How could we best test that?
kinghajj 14y ago
The Bohm interpretation has a universal wavefunction and non-locality, though.

Ingaz 14y ago

Correct if I'm wrong, but I think that Many Worlds Interpetation does not explain a thing. It's like religion - one can think it's possible, other - impossible. But it can't be proved or disproved

nessus42 14y ago
I'm pretty sure that, in theory, all the major interpretations of QM are experimentally distinguishable from each other. The feasibility of ever being able to perform some of these experiments, however, is rather questionable. Two exceptions to this are (1) that the Many Worlds Interpretation is experimentally indistinguishable from the Bohm Interpretation, unless you want to commit suicide many times with a quantum revolver; and (2) the Copenhagen Interpretation doesn't define what a "measurement" is, so scientifically determining whether it's correct or not is impossible. None of this implies that any of this is "like religion".
- pfedor 14y ago
  Be specific. What experiment do you have in mind that could distinguish between interpretations? Note that if the "experiment" involves dying to see what's on the other side then it doesn't exactly make it seem less like a religion.
  - nessus42 14y ago
    You might as well say that the Bohm interpretation is "like religion" then, rather than saying that the MWI is. If your assertion is that we might never know which is true, the Many Worlds Interpretation or the Bohm Interpretation, then you might be right. But, if it comes down to these two, most scientists are going to go with the Many Worlds Interpretation by Occam's razor. There are many other theories that we reject by Occam's razor that we can't disprove, and yet we don't typically consider these rejections to be a matter of "religion".
    - pfedor 14y ago
      You might as well say that the Bohm interpretation is "like religion" then, rather than saying that the MWI is. I might except MWI clearly has more True Believers. If your assertion is that we might never know which is true My assertion is that since all interpretations lead to the same exact predictions for every imaginable experiment, it doesn't make sense to say that in any meaningful way one interpretation is true and the others aren't. You might as well be arguing whether the electromagnetic field is weaved by tiny angels out of their hair or not. The Copenhagen interpretation is the closest to "no interpretation" in that it's the most direct way of translating the math into actual predictions. Quoting the guy who said you shouldn't multiply entities without necessity, to justify the introduction of infinitely many parallel worlds, is an interesting rhetorical maneuver.

kybernetikos 14y ago

Can you explain how MWI is local? In the period of time before the observer is 'entangled' into the same system as the observed particles, the different possibilities can interfere with each other. If this can happen even if the entangled particles are separated by a lot of space, surely that is the same as nonlocality. Maybe my confusion is that I'm not sure a which point the universe splits. Suppose I entangle two particles, then separate them by a large amount, my universe hasn't split yet, because before I make the measurement, I haven't become entangled with the state of the particles, but when I do, surely the spreading entanglement of myself with the possibilities centers at both entangled particles (i.e. it is nonlocal)?

kybernetikos 14y ago
Let me try to explain myself better: Two particles are entangled and separated by a vast distance. At some point, I conduct a measurement on the first particle, causing me to split into two different versions of myself that have measured two different states. Now, the effect of that measurement spreads outwards from the site of the measurement, so I may affect other things based on the measurement, etc. My problem is that if a measurement is done on the other particle, long before any message from me could possibly have got there, then that measurement and the effects it has on its local environment and the effects they have are all also dependent on my measurement. I imagine this as a wave of universe splitting spreading out from the site of my measurement and the entangled particle despite the separation. Now, perhaps this is a nontechnical use of the word nonlocal, but I'd describe that as a nonlocal phenomenon.
- nessus42 14y ago
  > My problem is that if a measurement is done on the other particle, long before any message from me could possibly have got there, then that measurement and the effects it has on its local environment and the effects they have are all also dependent on my measurement. Imagine that your friend Joe writes the same word on two pieces of paper, puts them in envelopes and hands one envelope to you and mails the other envelope to Paris. At some point in time, you open up your envelope and read the word "popcorn". At some other point in time, Pierre open up his envelope and reads the same word. The word that Pierre reads is not "dependent on your measurement". Nothing nonlocal occurred.