How is this a new paradox? Isn't this paradox the whole reason for different interpretations of Quantum Mechanics?
Physicists found a new quantum paradox that casts doubt on a pillar of reality
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Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality
#42> if the "friend" is a human-level artificial intelligence running in a massive quantum computer. Well, there's your problem right there. No AI can run on a quantum computer. Intelligence is inherently a classical phenomenon because it requires copying information, and quantum states cannot be copied, only classical states can be copied. The classical world "emerges" from the quantum world when you take a quantum sys…
> quantum states cannot be copied Wouldn't quantum entanglement enable a comparable ability?
Entanglement means that there are systems with highly (more-than-classically) correlated state - that the combined state is something that can’t be represented by considering the systems independently - not that the states are the same. The no-cloning theorem prohibits a process that takes the state of a system and replicates it on another system. It’s certainly possible to have or to generate entangled sets of systems that have identical separable state, but not to copy an arbitrary state.
Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality
#43The part that seems the most dubious to me is the "choice": > 2. It is possible to make free choices, or at least, statistically random choices. I don't see what would be really compelling in that. If it's false it would just mean that our actions are all kind of mechanistically decided by other events, and that does not shock me. Other point: > 1. When someone observes an event happening, it really happened. What if…
The main problem of quantum interpretation is the supposed, artificial, distinction between observer and observed system. In a quantum world this distinction is not possible, every event capable of "observing" a system is itself part of the system, modifying it. That's why such interpretations (postulating this separation) give all kinds of strange paradoxes that are impossible to solve. In the quantum world, there i…
Yes, I think you put your finger on it. As the observer is part of the system, his "reality" is as much superposed, entangled, etc., as the quantum events that compose it (himself and his observation too).
That would give credit to the multiverse interpretation of quantum mechanics then.
Maybe the observation process of a quantum phenomenon by a human observer is akin to the orthogonalization of a matrix:
as the observer becomes entangled with the observed particle, each possible observer-eigenstate (i.e. any observer in "his reality") ends up observing an eigenstate of the observed quantum phenomenon, instead of a dirty superposition.
To call it "orthogonalization of the observer-observed system" would be more descriptive than "wave-collapse", but the main difference is that the orthogonalization treats in parallel all possible outcomes, each linked to a different state (outcome) of the observer too, whereas the "collapse" view insists on the fact that the observed eigenstate is unique. And moreover, at least in mathematics, there are conditions for the orthogonalization to be possible at all, so that should be interesting.
Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality
#44The original Wigner's friend paradox: 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 be…
> 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 sub…
Multiple words modal logic; possibility mode monad.
Your friend is in the monad, now you are too. No big deal.
Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality
#45Earlier quoted context omitted.
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…
> 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.
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).
Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality
#46Earlier quoted context omitted.
> 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 sub…
Many-worlds interpretation takes care of this. Anyway, how do you know your experience of the world cannot be superposed? Have you ever been in superposition? We make up stories to maintain consistent histories all the time.
> how do you know your experience of the world cannot be superposed?
For your experience of the world to be superposed it would mean that you carry out a quantum experiment with two mutually exclusive outcomes |x> and |y> and you actually experience the superposed result |x>+|y>. This would be like opening the box in the Schroedinger's cat experiment and actually observing the cat to be |alive>+|dead>, instead of either alive or dead. Maybe it's possible, but such an experience has never been reported.
Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality
#47The original Wigner's friend paradox: 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 be…
> 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 sub…
The |y> superposition of you has one experience, and the |x> superposition of you has a different experience. The |y> version has no information about the |x> experience, and vice versa, because those two states are orthogonal in Hilbert space. This is essentially the prediction that results in the Everett many worlds interpretation.
If you somehow had an experience of "both outcomes simultaneously", that would violate the quantum mechanical prediction that there is no mutual information between the two superpositions. There are two brain states, an x state and a y state, and they know nothing about each other.
To each brain state (with the limited information available to it) it would appear that something "definite" had happened, even though in the global picture, a superposition still exists.
Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality
#48> Take a look at these three statements [...] they cannot all be true Okay, so we have to kill one. The easiest one to kill is > It is possible to make free choices. In other words, quantum mechanics is incompatible with free will. This is clearly shocking to any physicist who believes in Free Will (as defined by philosophers thousands of years ago). But hasn't Free Will been recognized as nonsense for at least two c…
> But hasn't Free Will been recognized as nonsense for at least two centuries by now?
Among some, sure and it's not just physicists [1].
Acknowledging that the concept we've called free will is not likely to be real has some troubling implications regarding how we've structured our society which is likely one of the reasons it's not talked about very often.
Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality
#49Earlier quoted context omitted.
> 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.
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).
So nothing has been gained by doing these experiments and publishing the results? I find that hard to believe.
Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality
#50Veritasium has a great video that explains the concept of parallel worlds vs wave collapse in a single world https://youtu.be/kTXTPe3wahc
Great video. I have a question though. Is there a non zero probability that any two versions of the same person in many worlds could interact with each other?