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The original Wigner's friend paradox: https://en.wikipedia.org/wiki/Wigner%27s_friend https://en.wikipedia.org/wiki/Wigner%27s_friend The paradox seems to rest

The original Wigner's friend paradox: https://en.wikipedia.org/wiki/Wigner%27s_friend https://en.wikipedia.org/wiki/Wigner%27s_friend The paradox seems to rest on magical thinking about consciousness, and if one simply accepts that a conscious observer can be in a superposition like any other piece of matter, the paradox is resolved. And, from the article: For Wigner, this was an absurd conclusion. Instead, he believed that once the consciousness of an observer becomes involved, the entanglement would “collapse” to make the friend’s observation definite. But what if Wigner was wrong? Well, obviously Wigner is wrong, sorry for being flippant. In this paper (preprint here: https://arxiv.org/pdf/1907.05607.pdf https://arxiv.org/pdf/1907.05607.pdf), the magical thinking about consciousness seems to be transmuted into "“Absoluteness of Observed Events” (i.e. that every observed event exists absolutely, not relatively)". The authors (it appears to me) mean by this that if an observer performs an experiment, while this observer is himself in a superposition, we have to regard the outcome of the experiment as absolute (i.e. not in a superposition) because it was made by a (conscious) observer. In my opinion, both "Absoluteness of Observed Events", and the equivalent from the layman's article, "When someone observes an event happening, it really happened", is a disingenuous and confusing way of talking about observers who are in a superposition. We have crossed over from "quantum mechanics is weird" to "these superficially intuitive but clearly false assumptions about quantum mechanics are weird". (by the way, I read the article here: https://theconversation.com/a-new-quantum-paradox-throws-the-foundations-of-observed-reality-into-question-144426 https://theconversation.com/a-new-quantum-paradox-throws-the... because that site doesn't think I'm a robot and then redirects me to the homepage after filling out the captcha)

TheOtherHobbes 6y ago
You might consider reading the original paper. Because the experiment doesn't rely on conscious observers at all. (Unless you think photons are conscious, which I'm assuming you don't.)
- bondarchuk 6y ago
  Well, that's the point. The experiment shows that one of three assumptions has to be false. But one of these (AOE) being false is not surprising or concerning at all, when dealing with non-conscious observers (such as photons, indeed). With conscious observers it would be concerning to some (not to me, but to Wigner and presumably the authors), because of the supposition that there's something special about conscious observers (i.e., magical thinking, IMHO). So what has this paper really shown? Absoluteness of Observed Events is false when the observers are photons, which (my layman's assumption) should surprise exactly nobody. And then they propose to repeat the experiment with an AI in a quantum computer as the observer. Lol.
  - guerrilla 6y ago
    > Absoluteness of Observed Events is false when the observers are photons, which (my layman's assumption) should surprise exactly nobody I'm with you but is this experimental result not new though? It seems like they're on our side and confirming what should be a non-surprising result, which is good work.
    - aeternum 6y ago
      Definitely not new, the double-slit experiment in 1801 first hinted that this might be the case, and then Heisenberg calculated exactly how 'not absolute' observed events are based on the wavelength (aka momentum) of the photon you're using (in 1927).
      - guerrilla 6y ago
        So nothing has been gained by doing these experiments and publishing the results? I find that hard to believe.
- scythmic_waves 6y ago
  > (Unless you think photons are conscious, which I'm assuming you don't.) Well, panpsychism is a thing and is actually having a bit of a renaissance.
devit 6y ago
It indeed seems so, i.e. that there is no paradox in the many-worlds and possibly other interpretations (as a non-expert in quantum physics). How did they manage to get the paper accepted in the (supposedly selective) Nature Physics journal though? Is there something we are missing?
- MrPatan 6y ago
  You're not missing anything. Maybe just the last step of lowering your opinion of the journal.
- GoblinSlayer 6y ago
  Such experiments criticize copenhagen interpretation, so as long as CI is moving, criticism is solid.
squibbles 6y ago
Translating the thought experiment to an actual physical experiment is something worth appreciating. A possible lack of absoluteness of observed events has implications for what observations may or may not be reconcilable using existing scientific methods.
canjobear 6y ago
> if one simply accepts that a conscious observer can be in a superposition like any other piece of matter, the paradox is resolved. It’s not so simple. Suppose you’re in a box and observe a quantum experiment, and then I open the box and observe you. Then before I open the box you’re in a superposed state |x> + |y>, corresponding to the two possible outcomes x and y. Fine, no problem so far. But what is your own subjective experience? You, subjectively, inside the box, will only ever observe yourself to be in |x> or |y>, never |x> + |y>. Even if from the outside your brain can be said to be in a superposed state, your experience of the world is not superposed.
- oopsiforgot7 6y ago
  If you embrace many worlds all these issues go away.
  - phkahler 6y ago
    Or if you embrace nonlocality.
    - undreren 6y ago
      Wouldn’t that imply FTL travel, at least for information?
      - tsimionescu 6y ago
        No, non-locality simply means that effects happen at infinite speeds, not that they carry information. For example, the Copenhagen interpretation of QM abandons both locality and realism - particles don't have definite states, and they also communicate at infinite speed (but in a way that can't carry information).
        undreren 6y ago
        What does it mean to communicate without information? That genuinely sounds like an oxymoron.
brundolf 6y ago
It's interesting the way some scientists have been biased into this kind of magical thinking, probably because the integrity of conscious observation is so central to their practice/worldview. Nobody is free from the pressure of cognitive dissonance.
kmm 6y ago
We're veering away from physics here, but isn't consciousness actually quite "magical". It's beyond remarkable to me that stimulating nervous tissue, composed of quite mundane things like protons and electrons, yields a subjective experience. I know many people reject the hard problem of consciousness, but to those who don't, the implications of thought experiments like Wigner's friend, like superpositions or entanglement of subjective experiences, are truly paradoxical. You are calling certain viewpoints obviously wrong or false because you adhere to certain philosophical viewpoints. There's nothing wrong with that, and they're all justifiable, but none of them are complete consensus among philosophers. Coming back to physics, there's an assumption you and other commenters are silently making, which is that quantum mechanics is even applicable to macroscopic objects like humans. The largest objects which have been shown to act wave-like are a few thousand atoms large. While it's indisputable that at the lowest level the universe is fundamentally quantum mechanical, it's a little brazen to extrapolate that over more than 20 orders of magnitude. As a physicist myself, I'll believe it when I see it, and I'm looking forward to getting results from proposed experiments like FELIX and its successors. https://en.wikipedia.org/wiki/Free-orbit_experiment_with_laser_interferometry_X-rays https://en.wikipedia.org/wiki/Free-orbit_experiment_with_las...
- deleted 6y ago
  [deleted]
- keymone 6y ago
  Pretty sure I’m dunnig-krugering this, but is consciousness really that magical? Nervous system evolved from ability to respond to external stimuli to centralized control of various processes to evaluation of risks/benefits of actions and finally to predictive modeling of external processes. Rudimentary concept of “self” and understanding of surrounding environment exists in various animals, so why is it strange that an animal with most complex brain has the most sophisticated concept of “self” and it’s placement in the ultimate surrounding environment - the universe?
  - kmm 6y ago
    Of course, apart from how the actual implementation works I don't think many people have a problem with that. And if it was just that, Wigner's friend wouldn't be nearly as interesting, it would suffice to say that if quantum mechanical effects really keep working all the way up to the macroscopic level (which again is anything but obvious), that his friend's body and brain would simply be in a superposition of both states. But this understand of the surroundings and capability to react to stimuli comes with a subjective experience, which is what is actually meant with "consciousness". This is the hard problem of consciousness[0]. 0: https://en.wikipedia.org/wiki/Hard_problem_of_consciousness https://en.wikipedia.org/wiki/Hard_problem_of_consciousness
nmlnn 6y ago
Great mindscape podcast about how the magical thinking developed: https://www.preposterousuniverse.com/podcast/2019/03/04/episode-36-david-albert-on-quantum-measurement-and-the-problems-with-many-worlds/ https://www.preposterousuniverse.com/podcast/2019/03/04/epis...
freeexpression 6y ago
Article is hard to read since someone butchered it for ideological reasons: https://en.wikipedia.org/w/index.php?title=Wigner%27s_friend&oldid=903263587 https://en.wikipedia.org/w/index.php?title=Wigner%27s_friend...
francasso 6y ago
Sorry but there is nothing obvious about any of it. It all boils down to the measurement problem and entanglement. While I don't like psi-epistemic interpretations either, it's not like there is anything clearly inconsistent with them, or like psi-ontic and psi-complete interpretations make more sense or are devoid of issues. They all have problems and make assumptions that are hard to swallow, and if you believe any of them and start ridiculing others you are pretty much picking sides with no good evidence. So while you might have already pledged your faith, other people with probably as much understanding of the issues or more haven't.
Thorentis 6y ago
From the Wikipedia: > "From the point of view of the friend, the measurement result was determined long before Wigner had asked about it, and the state of the physical system has already collapsed. When now exactly did the collapse occur? Was it when the friend had finished their measurement, or when the information of its result entered Wigner's consciousness?" This to me, shows just how hand-wavy the whole superposition/quantum collapse stuff really is. I have to say I side with Einstein with his view that everything is already in one state or the other. We don't cause the system to choose a state when we measure it. We simply discover the state it was already in. It is one thing to assign a probability to which state we will find it in. It is quite another to create an entire theory around quantum measurement. There is nothing mysterious about this paradox. The friend performs the measurement ans discovers the state of the particle/system. Wiger doesn't know about it, but that doesn't mean it's not in that state, he just isn't aware of it yet. The fact this is a paradox just seems like silly mind games.
- incognition 6y ago
  QM is not hand wavy and gives precise results for many practical problems. Your theory is wrong as per one of the simplest quantum experiment - the single electron double slit problem.
  - Thorentis 6y ago
    The variation of the double split experiment that supposedly proves that observance "changes" the outcome, is only a thought experiment, and therefore can be flawed due to incorrect thinking. Obviously, the basic double slit experiment which shows the wave/particle duality of light is done in practice and therefore empirical.
    - gonnano 6y ago
      I like most on here have followed your thinking at some point, but have had to ditch our intuition along with comman sense and a good part of our sanity when we found out we were lost down the rabbit hole after schrodinger's cat ate our breadcrumbs. An observer changing the outcome is a very real repeatable experiment with non wavey results. https://physicsworld.com/a/do-atoms-going-through-a-double-slit-know-if-they-are-being-observed https://physicsworld.com/a/do-atoms-going-through-a-double-s... It's similar to the problem that has been highlighted here by OP, to quote the artical I posted "Indeed, the results of both Truscott and Aspect’s experiments shows that a particle’s wave or particle nature is most likely undefined until a measurement is made. The other less likely option would be that of backward causation – that the particle somehow has information from the future – but this involves sending a message faster than light, which is forbidden by the rules of relativity. "

TheOtherHobbes 6y ago

You might consider reading the original paper. Because the experiment doesn't rely on conscious observers at all. (Unless you think photons are conscious, which I'm assuming you don't.)

bondarchuk 6y ago
Well, that's the point. The experiment shows that one of three assumptions has to be false. But one of these (AOE) being false is not surprising or concerning at all, when dealing with non-conscious observers (such as photons, indeed). With conscious observers it would be concerning to some (not to me, but to Wigner and presumably the authors), because of the supposition that there's something special about conscious observers (i.e., magical thinking, IMHO). So what has this paper really shown? Absoluteness of Observed Events is false when the observers are photons, which (my layman's assumption) should surprise exactly nobody. And then they propose to repeat the experiment with an AI in a quantum computer as the observer. Lol.
- guerrilla 6y ago
  > Absoluteness of Observed Events is false when the observers are photons, which (my layman's assumption) should surprise exactly nobody I'm with you but is this experimental result not new though? It seems like they're on our side and confirming what should be a non-surprising result, which is good work.
  - aeternum 6y ago
    Definitely not new, the double-slit experiment in 1801 first hinted that this might be the case, and then Heisenberg calculated exactly how 'not absolute' observed events are based on the wavelength (aka momentum) of the photon you're using (in 1927).
    - guerrilla 6y ago
      So nothing has been gained by doing these experiments and publishing the results? I find that hard to believe.
scythmic_waves 6y ago
> (Unless you think photons are conscious, which I'm assuming you don't.) Well, panpsychism is a thing and is actually having a bit of a renaissance.

devit 6y ago

It indeed seems so, i.e. that there is no paradox in the many-worlds and possibly other interpretations (as a non-expert in quantum physics). How did they manage to get the paper accepted in the (supposedly selective) Nature Physics journal though? Is there something we are missing?

MrPatan 6y ago
You're not missing anything. Maybe just the last step of lowering your opinion of the journal.
GoblinSlayer 6y ago
Such experiments criticize copenhagen interpretation, so as long as CI is moving, criticism is solid.

squibbles 6y ago

Translating the thought experiment to an actual physical experiment is something worth appreciating. A possible lack of absoluteness of observed events has implications for what observations may or may not be reconcilable using existing scientific methods.

canjobear 6y ago

> if one simply accepts that a conscious observer can be in a superposition like any other piece of matter, the paradox is resolved. It’s not so simple. Suppose you’re in a box and observe a quantum experiment, and then I open the box and observe you. Then before I open the box you’re in a superposed state |x> + |y>, corresponding to the two possible outcomes x and y. Fine, no problem so far. But what is your own subjective experience? You, subjectively, inside the box, will only ever observe yourself to be in |x> or |y>, never |x> + |y>. Even if from the outside your brain can be said to be in a superposed state, your experience of the world is not superposed.

oopsiforgot7 6y ago
If you embrace many worlds all these issues go away.
- phkahler 6y ago
  Or if you embrace nonlocality.
  - undreren 6y ago
    Wouldn’t that imply FTL travel, at least for information?
    - tsimionescu 6y ago
      No, non-locality simply means that effects happen at infinite speeds, not that they carry information. For example, the Copenhagen interpretation of QM abandons both locality and realism - particles don't have definite states, and they also communicate at infinite speed (but in a way that can't carry information).
      - undreren 6y ago
        What does it mean to communicate without information? That genuinely sounds like an oxymoron.

brundolf 6y ago

It's interesting the way some scientists have been biased into this kind of magical thinking, probably because the integrity of conscious observation is so central to their practice/worldview. Nobody is free from the pressure of cognitive dissonance.

kmm 6y ago

We're veering away from physics here, but isn't consciousness actually quite "magical". It's beyond remarkable to me that stimulating nervous tissue, composed of quite mundane things like protons and electrons, yields a subjective experience. I know many people reject the hard problem of consciousness, but to those who don't, the implications of thought experiments like Wigner's friend, like superpositions or entanglement of subjective experiences, are truly paradoxical. You are calling certain viewpoints obviously wrong or false because you adhere to certain philosophical viewpoints. There's nothing wrong with that, and they're all justifiable, but none of them are complete consensus among philosophers. Coming back to physics, there's an assumption you and other commenters are silently making, which is that quantum mechanics is even applicable to macroscopic objects like humans. The largest objects which have been shown to act wave-like are a few thousand atoms large. While it's indisputable that at the lowest level the universe is fundamentally quantum mechanical, it's a little brazen to extrapolate that over more than 20 orders of magnitude. As a physicist myself, I'll believe it when I see it, and I'm looking forward to getting results from proposed experiments like FELIX and its successors. https://en.wikipedia.org/wiki/Free-orbit_experiment_with_laser_interferometry_X-rays https://en.wikipedia.org/wiki/Free-orbit_experiment_with_las...

deleted 6y ago
[deleted]
keymone 6y ago
Pretty sure I’m dunnig-krugering this, but is consciousness really that magical? Nervous system evolved from ability to respond to external stimuli to centralized control of various processes to evaluation of risks/benefits of actions and finally to predictive modeling of external processes. Rudimentary concept of “self” and understanding of surrounding environment exists in various animals, so why is it strange that an animal with most complex brain has the most sophisticated concept of “self” and it’s placement in the ultimate surrounding environment - the universe?
- kmm 6y ago
  Of course, apart from how the actual implementation works I don't think many people have a problem with that. And if it was just that, Wigner's friend wouldn't be nearly as interesting, it would suffice to say that if quantum mechanical effects really keep working all the way up to the macroscopic level (which again is anything but obvious), that his friend's body and brain would simply be in a superposition of both states. But this understand of the surroundings and capability to react to stimuli comes with a subjective experience, which is what is actually meant with "consciousness". This is the hard problem of consciousness[0]. 0: https://en.wikipedia.org/wiki/Hard_problem_of_consciousness https://en.wikipedia.org/wiki/Hard_problem_of_consciousness

nmlnn 6y ago

Great mindscape podcast about how the magical thinking developed: https://www.preposterousuniverse.com/podcast/2019/03/04/episode-36-david-albert-on-quantum-measurement-and-the-problems-with-many-worlds/ https://www.preposterousuniverse.com/podcast/2019/03/04/epis...

freeexpression 6y ago

Article is hard to read since someone butchered it for ideological reasons: https://en.wikipedia.org/w/index.php?title=Wigner%27s_friend&oldid=903263587 https://en.wikipedia.org/w/index.php?title=Wigner%27s_friend...

francasso 6y ago

Sorry but there is nothing obvious about any of it. It all boils down to the measurement problem and entanglement. While I don't like psi-epistemic interpretations either, it's not like there is anything clearly inconsistent with them, or like psi-ontic and psi-complete interpretations make more sense or are devoid of issues. They all have problems and make assumptions that are hard to swallow, and if you believe any of them and start ridiculing others you are pretty much picking sides with no good evidence. So while you might have already pledged your faith, other people with probably as much understanding of the issues or more haven't.

Thorentis 6y ago

From the Wikipedia: > "From the point of view of the friend, the measurement result was determined long before Wigner had asked about it, and the state of the physical system has already collapsed. When now exactly did the collapse occur? Was it when the friend had finished their measurement, or when the information of its result entered Wigner's consciousness?" This to me, shows just how hand-wavy the whole superposition/quantum collapse stuff really is. I have to say I side with Einstein with his view that everything is already in one state or the other. We don't cause the system to choose a state when we measure it. We simply discover the state it was already in. It is one thing to assign a probability to which state we will find it in. It is quite another to create an entire theory around quantum measurement. There is nothing mysterious about this paradox. The friend performs the measurement ans discovers the state of the particle/system. Wiger doesn't know about it, but that doesn't mean it's not in that state, he just isn't aware of it yet. The fact this is a paradox just seems like silly mind games.

incognition 6y ago
QM is not hand wavy and gives precise results for many practical problems. Your theory is wrong as per one of the simplest quantum experiment - the single electron double slit problem.
- Thorentis 6y ago
  The variation of the double split experiment that supposedly proves that observance "changes" the outcome, is only a thought experiment, and therefore can be flawed due to incorrect thinking. Obviously, the basic double slit experiment which shows the wave/particle duality of light is done in practice and therefore empirical.
  - gonnano 6y ago
    I like most on here have followed your thinking at some point, but have had to ditch our intuition along with comman sense and a good part of our sanity when we found out we were lost down the rabbit hole after schrodinger's cat ate our breadcrumbs. An observer changing the outcome is a very real repeatable experiment with non wavey results. https://physicsworld.com/a/do-atoms-going-through-a-double-slit-know-if-they-are-being-observed https://physicsworld.com/a/do-atoms-going-through-a-double-s... It's similar to the problem that has been highlighted here by OP, to quote the artical I posted "Indeed, the results of both Truscott and Aspect’s experiments shows that a particle’s wave or particle nature is most likely undefined until a measurement is made. The other less likely option would be that of backward causation – that the particle somehow has information from the future – but this involves sending a message faster than light, which is forbidden by the rules of relativity. "