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A recent experiment seems to confirm that different observers see conflicting realities: https://www.technologyreview.com/s/613092/a-quantum-experiment-suggests

A recent experiment seems to confirm that different observers see conflicting realities: https://www.technologyreview.com/s/613092/a-quantum-experiment-suggests-theres-no-such-thing-as-objective-reality/ https://www.technologyreview.com/s/613092/a-quantum-experime...

atq2119 7y ago
Honest question: Do physicists studying these problems genuinely believe that these experiments show some kind of conflict or paradox, or is this just a case of people writing clickbait articles? I'm not a physicist and only dug deeply enough into the topic to understand the basic quantum algorithms for factoring and discrete logarithm, but it seems to me that there is very obviously no conflict. It's just that the "observer of the observer" observes a meta-reality that contains all possible realities observed by the "observer". There doesn't seem anything strange about this if you just don't insist on "measurement" having a special physical meaning and accept the universal wave function. But maybe there's a twist I'm missing.
- lisper 7y ago
  > Do physicists studying these problems genuinely believe that these experiments show some kind of conflict or paradox, or is this just a case of people writing clickbait articles? The latter. QM is weird, but it's not paradoxical.
- Viliam1234 7y ago
  Not a physicist either, but seems to me that the whole issue is people refusing to admit that they are themselves composed of atoms that follow the laws of quantum physics. If a set of atoms can be in a superposition, so can be you. Because you are a set of atoms, duh.
  - millstone 7y ago
    All physicists acknowledge they are composed of atoms, duh! It does not follow that "if a set of atoms can be in a superposition, so can you." Here's some ways it might fail: 1. In the objective collapse theories, quantum systems undergo collapse when they reach a certain size. I cannot be in a superposition because I am physically too big. 2. In the ensemble interpretations, a quantum state applies to a set of many identically prepared systems. Since there is only one of me, we cannot speak meaningfully of my quantum properties. Admittedly neither of these are satisfying interpretations, but they have their proponents. The deeper objection is that "you can be in a superposition" risks detachment from experiments. If we cannot talk about the result of an experiment, that we cannot do science.
- antidesitter 7y ago
  It’s clickbait. These experiments show no inconsistency in quantum mechanics, which can be easily seen if you think about the whole system as a single wavefunction under unitary evolution. And as someone else mentioned, “observers” are part of that wavefunction. Fundamentally, they follow the same rules.
- andreareina 7y ago
  Depends on your view of what's going on under the covers. > From the friend’s perspective, the qubit has been measured and has collapsed to either |0〉 or |1〉. From Wigner’s perspective, no such thing has happened—there’s only been unitary evolution—and in principle, Wigner could even confirm that by measuring |ψ〉 in a basis that included |ψ〉 as one of the basis vectors. But how can they both be right? > Many-Worlders will yawn at this question, since for them, of course “the collapse of the wavefunction” is just an illusion created by the branching worlds, and with sufficiently advanced technology, one observer might experience the illusion even while a nearby observer doesn’t. Ironically, the neo-Copenhagenists / Quantum Bayesians / whatever they now call themselves, though they consider themselves diametrically opposed to the Many-Worlders (and vice versa), will also yawn at the question, since their whole philosophy is about how physics is observer-relative and it’s sinful even to think about an objective, God-given “quantum state of the universe.” If, on the other hand, you believed both that > 1. collapse is an objective physical event, and > 2. human mental states can be superposed just like anything else in the physical universe, > then Wigner’s thought experiment probably should rock your world. https://www.scottaaronson.com/blog/?p=3975 https://www.scottaaronson.com/blog/?p=3975

atq2119 7y ago

Honest question: Do physicists studying these problems genuinely believe that these experiments show some kind of conflict or paradox, or is this just a case of people writing clickbait articles? I'm not a physicist and only dug deeply enough into the topic to understand the basic quantum algorithms for factoring and discrete logarithm, but it seems to me that there is very obviously no conflict. It's just that the "observer of the observer" observes a meta-reality that contains all possible realities observed by the "observer". There doesn't seem anything strange about this if you just don't insist on "measurement" having a special physical meaning and accept the universal wave function. But maybe there's a twist I'm missing.

lisper 7y ago
> Do physicists studying these problems genuinely believe that these experiments show some kind of conflict or paradox, or is this just a case of people writing clickbait articles? The latter. QM is weird, but it's not paradoxical.
Viliam1234 7y ago
Not a physicist either, but seems to me that the whole issue is people refusing to admit that they are themselves composed of atoms that follow the laws of quantum physics. If a set of atoms can be in a superposition, so can be you. Because you are a set of atoms, duh.
- millstone 7y ago
  All physicists acknowledge they are composed of atoms, duh! It does not follow that "if a set of atoms can be in a superposition, so can you." Here's some ways it might fail: 1. In the objective collapse theories, quantum systems undergo collapse when they reach a certain size. I cannot be in a superposition because I am physically too big. 2. In the ensemble interpretations, a quantum state applies to a set of many identically prepared systems. Since there is only one of me, we cannot speak meaningfully of my quantum properties. Admittedly neither of these are satisfying interpretations, but they have their proponents. The deeper objection is that "you can be in a superposition" risks detachment from experiments. If we cannot talk about the result of an experiment, that we cannot do science.
antidesitter 7y ago
It’s clickbait. These experiments show no inconsistency in quantum mechanics, which can be easily seen if you think about the whole system as a single wavefunction under unitary evolution. And as someone else mentioned, “observers” are part of that wavefunction. Fundamentally, they follow the same rules.
andreareina 7y ago
Depends on your view of what's going on under the covers. > From the friend’s perspective, the qubit has been measured and has collapsed to either |0〉 or |1〉. From Wigner’s perspective, no such thing has happened—there’s only been unitary evolution—and in principle, Wigner could even confirm that by measuring |ψ〉 in a basis that included |ψ〉 as one of the basis vectors. But how can they both be right? > Many-Worlders will yawn at this question, since for them, of course “the collapse of the wavefunction” is just an illusion created by the branching worlds, and with sufficiently advanced technology, one observer might experience the illusion even while a nearby observer doesn’t. Ironically, the neo-Copenhagenists / Quantum Bayesians / whatever they now call themselves, though they consider themselves diametrically opposed to the Many-Worlders (and vice versa), will also yawn at the question, since their whole philosophy is about how physics is observer-relative and it’s sinful even to think about an objective, God-given “quantum state of the universe.” If, on the other hand, you believed both that > 1. collapse is an objective physical event, and > 2. human mental states can be superposed just like anything else in the physical universe, > then Wigner’s thought experiment probably should rock your world. https://www.scottaaronson.com/blog/?p=3975 https://www.scottaaronson.com/blog/?p=3975