5 ms·

Most of the times that's because we find it hard to imagine how it would "feel" being ourselves entangled with the thing we observe. Accepting that there is eff

Most of the times that's because we find it hard to imagine how it would "feel" being ourselves entangled with the thing we observe. Accepting that there is effectively a copy of you that is effectively fully casually disconnected from you goes strongly against our instinct that wants us to be "us" unique and objectively existing

neom 3y ago
Can you dive into this a little more? I think I understand what you're saying but it's a very interesting idea and I'd love to understand it more if you don't mind. :)
- eurier_br 3y ago
  I, personally (and a bunch of other physicists), think that the issue is not exactly the entanglement. If you take a pair of gloves and send each piece to two separate people, the moment either of them open the box they will know instantly which piece (left or right) the other got, because both of them knows that a pair of gloves comes with a right piece and a left piece. This is why entanglement doesn't violate general relativity, each person updates their knowledge instantaneously but there is no flow of information from one person to the other. The true issue, according to some people (me, an experimental materials science-focused physicist, included), is the measurement problem. It updates the state of entangled systems instantaneously, including very space-separated systems. In this way the measurement is provokes the collapse of the quantum state in a non-local way. The problem is that the effects of measurement in quantum systems described by a postulate in quantum theory. So, in my opinion, the non-locality remains not explained and is generally neglected as a non-issue by the community at large.
  - bowsamic 3y ago
    > I, personally (and a bunch of other physicists), think that the issue is not exactly the entanglement. If you take a pair of gloves and send each piece to two separate people, the moment either of them open the box they will know instantly which piece (left or right) the other got, because both of them knows that a pair of gloves comes with a right piece and a left piece. This is why entanglement doesn't violate general relativity, each person updates their knowledge instantaneously but there is no flow of information from one person to the other. Quantum entanglement is different though than the classical case you describe. There is no classical correlation that is as strong as the quantum correlations. That's what Bell proved in his theorem: if you only have local interactions and assume that the two systems are correlated and actually already have the states really and we are simply ignorant of them, then the amount of correlation you get between the two systems is smaller than the amount of correlation that quantum mechanics predicts, and the amount verified by quantum experiments. Therefore, the explanation you describe is not adequate to explain quantum mechanics. It explains how there can be correlations without the need to transfer information, however the amount of correlation this predicts is smaller than the quantum correlation. (Aside: that is, unless, you drop the condition for statistical independence of your measurements, i.e., you assume you are free to choose which measurement to do. If you drop this assumption, this interpretation is called superdeterminism) > The true issue, according to some people (me, an experimental materials science-focused physicist, included), is the measurement problem. It updates the state of entangled systems instantaneously, including very space-separated systems. In this way the measurement is provokes the collapse of the quantum state in a non-local way. The problem is that the effects of measurement in quantum systems described by a postulate in quantum theory. So, in my opinion, the non-locality remains not explained and is generally neglected as a non-issue by the community at large. I don't see what the measurement problem has to do with locality. If the interpretation of quantum entanglement that you described above was correct, this would also explain the measurement problem. The problem with measurement is more that it is non-unitary. Most likely imo, measurement is an unrealistic abstraction of a complex interaction, which only appears to be non-unitary on the face of it.
    - eurier_br 3y ago
      >Quantum entanglement is different though than the classical case you describe. There is no classical correlation that is as strong as the quantum correlations. That's what Bell proved in his theorem: if you only have local interactions and assume that the two systems are correlated and actually already have the states really and we are simply ignorant of them, then the amount of correlation you get between the two systems is smaller than the amount of correlation that quantum mechanics predicts, and the amount verified by quantum experiments. First of all, I kind agree with you. After all, the experimental observation of the violation of the Bell inequality is a landmark win for the probabilistic nature of quantum mechanics and it is undeniable. Also, the gloves example is just a particular case of "Bell's theorem experiment" with sensors aligned along the quantization axis of the conserved observable being measured (Measuring Sz in superposition of |+>z and |->z, for example). Second, I used this example to simply say that "there can be correlations without the need to transfer information" at superluminal speeds. That is, entanglement either quantum or classical is not incompatible with general relativity nor non-local. >I don't see what the measurement problem has to do with locality. In the way I understand Bell's theorem (keeping statistical independence), it mainly tells us that i) if there is a hidden variables theory that explains QM results, it needs to be non-local. And, ii) if there is not a hidden variables theory, the state prior to the measurement is truly indetermined in the sense that we are not simply ignorant of the true state. For me, ii) introduces non-locality in the sense that measuring one entangled particle will change the state of particle 2 irrespectively of time-space separation. You can say that there is no such a thing "state of particle 2" there is just the "entangled state". But this, in turn, invites the discussions of "physicness", "realness", etc of "states" and "wavefunctions". Which seem to be sidestepped due to the overwhelming success of the theory. >The problem with measurement is more that it is non-unitary. I am not aware of the consequences of this. If not too bothersome, could you discuss possible (EDIT: possible consequences that impact) experimental results of this? Thanks
      - bowsamic 3y ago
        > You can say that there is no such a thing "state of particle 2" there is just the "entangled state". But this, in turn, invites the discussions of "physicness", "realness", etc of "states" and "wavefunctions". Which seem to be sidestepped due to the overwhelming success of the theory. I mean, we could sidestep it, but it's a fundamental part of the formalism of quantum mechanics. It's even worse if we consider quantum gravity: is the spacetime also in a non-separable state? I'm not sure about local non-hidden variable theories though, to be honest > If not too bothersome, could you discuss possible (EDIT: possible consequences that impact) experimental results of this? There are none
bowsamic 3y ago
It has nothing to do with instincts or what is easy or hard to imagine, it's almost always because of special relativity and that all of our theories of the different forces are all local. If entanglement is the only non-local interaction, then why? I don't think it has anything to do with the human's idea of themselves EDIT: If you meant why people accept it, well that's for the same reason that the EPR paradox was formulated in the first place: the basic formulation of quantum mechanics and the most obvious interpretation of it basically straight up says there is non-local action
- ithkuil 3y ago
  I poorly phrased my comment. You don't have to give up locality it you just accept that we as observers get entangled with what we observe and the wave function doesn't really collapse. This is compatible with bell inequality and with locality. See Everett or many-worls interpretation
  - bowsamic 3y ago
    There are interpretations of quantum mechanics covering all possible situations, but we don't have a way of choosing between them. You are suggesting religion, not science, not even philosophy.
    - ithkuil 3y ago
      I don't think that's fair. The Everett interpretation is just taking the Schrödinger equations and not adding anything else to it. The "interpretation" part is just about explaining how to make sense of what _we_ see and how to make that compatible with the Schrödinger equation. There is nothing mystic about it, quite the contrary I posit, the rejection of it requires the introduction of something anti-scientific, namely that we humans are somehow special and detached from the physical world
      - bowsamic 3y ago
        > The Everett interpretation is just taking the Schrödinger equations and not adding anything else to it. That's literally what people claim Copenhagen to be Everett's interpretation requires positing a universal wavefunction and some kind of branching mechanism It's not some basic, straightforward interpretation of QM without any additional postulates, and even if it was, that would not be evidence for it to be true over others

neom 3y ago

Can you dive into this a little more? I think I understand what you're saying but it's a very interesting idea and I'd love to understand it more if you don't mind. :)

eurier_br 3y ago
I, personally (and a bunch of other physicists), think that the issue is not exactly the entanglement. If you take a pair of gloves and send each piece to two separate people, the moment either of them open the box they will know instantly which piece (left or right) the other got, because both of them knows that a pair of gloves comes with a right piece and a left piece. This is why entanglement doesn't violate general relativity, each person updates their knowledge instantaneously but there is no flow of information from one person to the other. The true issue, according to some people (me, an experimental materials science-focused physicist, included), is the measurement problem. It updates the state of entangled systems instantaneously, including very space-separated systems. In this way the measurement is provokes the collapse of the quantum state in a non-local way. The problem is that the effects of measurement in quantum systems described by a postulate in quantum theory. So, in my opinion, the non-locality remains not explained and is generally neglected as a non-issue by the community at large.
- bowsamic 3y ago
  > I, personally (and a bunch of other physicists), think that the issue is not exactly the entanglement. If you take a pair of gloves and send each piece to two separate people, the moment either of them open the box they will know instantly which piece (left or right) the other got, because both of them knows that a pair of gloves comes with a right piece and a left piece. This is why entanglement doesn't violate general relativity, each person updates their knowledge instantaneously but there is no flow of information from one person to the other. Quantum entanglement is different though than the classical case you describe. There is no classical correlation that is as strong as the quantum correlations. That's what Bell proved in his theorem: if you only have local interactions and assume that the two systems are correlated and actually already have the states really and we are simply ignorant of them, then the amount of correlation you get between the two systems is smaller than the amount of correlation that quantum mechanics predicts, and the amount verified by quantum experiments. Therefore, the explanation you describe is not adequate to explain quantum mechanics. It explains how there can be correlations without the need to transfer information, however the amount of correlation this predicts is smaller than the quantum correlation. (Aside: that is, unless, you drop the condition for statistical independence of your measurements, i.e., you assume you are free to choose which measurement to do. If you drop this assumption, this interpretation is called superdeterminism) > The true issue, according to some people (me, an experimental materials science-focused physicist, included), is the measurement problem. It updates the state of entangled systems instantaneously, including very space-separated systems. In this way the measurement is provokes the collapse of the quantum state in a non-local way. The problem is that the effects of measurement in quantum systems described by a postulate in quantum theory. So, in my opinion, the non-locality remains not explained and is generally neglected as a non-issue by the community at large. I don't see what the measurement problem has to do with locality. If the interpretation of quantum entanglement that you described above was correct, this would also explain the measurement problem. The problem with measurement is more that it is non-unitary. Most likely imo, measurement is an unrealistic abstraction of a complex interaction, which only appears to be non-unitary on the face of it.
  - eurier_br 3y ago
    >Quantum entanglement is different though than the classical case you describe. There is no classical correlation that is as strong as the quantum correlations. That's what Bell proved in his theorem: if you only have local interactions and assume that the two systems are correlated and actually already have the states really and we are simply ignorant of them, then the amount of correlation you get between the two systems is smaller than the amount of correlation that quantum mechanics predicts, and the amount verified by quantum experiments. First of all, I kind agree with you. After all, the experimental observation of the violation of the Bell inequality is a landmark win for the probabilistic nature of quantum mechanics and it is undeniable. Also, the gloves example is just a particular case of "Bell's theorem experiment" with sensors aligned along the quantization axis of the conserved observable being measured (Measuring Sz in superposition of |+>z and |->z, for example). Second, I used this example to simply say that "there can be correlations without the need to transfer information" at superluminal speeds. That is, entanglement either quantum or classical is not incompatible with general relativity nor non-local. >I don't see what the measurement problem has to do with locality. In the way I understand Bell's theorem (keeping statistical independence), it mainly tells us that i) if there is a hidden variables theory that explains QM results, it needs to be non-local. And, ii) if there is not a hidden variables theory, the state prior to the measurement is truly indetermined in the sense that we are not simply ignorant of the true state. For me, ii) introduces non-locality in the sense that measuring one entangled particle will change the state of particle 2 irrespectively of time-space separation. You can say that there is no such a thing "state of particle 2" there is just the "entangled state". But this, in turn, invites the discussions of "physicness", "realness", etc of "states" and "wavefunctions". Which seem to be sidestepped due to the overwhelming success of the theory. >The problem with measurement is more that it is non-unitary. I am not aware of the consequences of this. If not too bothersome, could you discuss possible (EDIT: possible consequences that impact) experimental results of this? Thanks
    - bowsamic 3y ago
      > You can say that there is no such a thing "state of particle 2" there is just the "entangled state". But this, in turn, invites the discussions of "physicness", "realness", etc of "states" and "wavefunctions". Which seem to be sidestepped due to the overwhelming success of the theory. I mean, we could sidestep it, but it's a fundamental part of the formalism of quantum mechanics. It's even worse if we consider quantum gravity: is the spacetime also in a non-separable state? I'm not sure about local non-hidden variable theories though, to be honest > If not too bothersome, could you discuss possible (EDIT: possible consequences that impact) experimental results of this? There are none

bowsamic 3y ago

It has nothing to do with instincts or what is easy or hard to imagine, it's almost always because of special relativity and that all of our theories of the different forces are all local. If entanglement is the only non-local interaction, then why? I don't think it has anything to do with the human's idea of themselves EDIT: If you meant why people accept it, well that's for the same reason that the EPR paradox was formulated in the first place: the basic formulation of quantum mechanics and the most obvious interpretation of it basically straight up says there is non-local action

ithkuil 3y ago
I poorly phrased my comment. You don't have to give up locality it you just accept that we as observers get entangled with what we observe and the wave function doesn't really collapse. This is compatible with bell inequality and with locality. See Everett or many-worls interpretation
- bowsamic 3y ago
  There are interpretations of quantum mechanics covering all possible situations, but we don't have a way of choosing between them. You are suggesting religion, not science, not even philosophy.
  - ithkuil 3y ago
    I don't think that's fair. The Everett interpretation is just taking the Schrödinger equations and not adding anything else to it. The "interpretation" part is just about explaining how to make sense of what _we_ see and how to make that compatible with the Schrödinger equation. There is nothing mystic about it, quite the contrary I posit, the rejection of it requires the introduction of something anti-scientific, namely that we humans are somehow special and detached from the physical world
    - bowsamic 3y ago
      > The Everett interpretation is just taking the Schrödinger equations and not adding anything else to it. That's literally what people claim Copenhagen to be Everett's interpretation requires positing a universal wavefunction and some kind of branching mechanism It's not some basic, straightforward interpretation of QM without any additional postulates, and even if it was, that would not be evidence for it to be true over others