This is the video that finally made it click for me[1]. Despite the somewhat click-baity title ("What Popularizers of QM Don't Want You to Know") it actually goes into quite a bit of detail of what is and isn't a measurement, in the sense of interactions in a quantum mechanical system that strongly resemble classical behavior (it can be said that the quantum mechanical world is a simulator that can run classical mechanics).
A wave function does not collapse upon detection?
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Re: A wave function does not collapse upon detection?
#42There's a difference between strong and weak quantum measurements. Experimentally we can now even apply feedback on quantum states to stabilize them, which requires making partial, non-destructive measurements of a quantum state and then applying signals to correct deviations. The whole talk about "wave function collapse" originated from the beginnings of quantum mechanics where the measurement process was poorly und…
I think the most reasonable explanation is that unobserved things do not happen, at all, or only happen on some abstract statistical level. That doesn't imply that consciousness is special. The reason why you are aware of reading this, if you are indeed aware of reading this, is that your life matters for some future event, which on the fundamental physical level has already happened, but its exact results depends on…
What's that "meow" sound I hear coming from that box over there?
Re: A wave function does not collapse upon detection?
#43> But surely the wave function is smeared across both slits That's the whole point of the experiment - you can't get an interference pattern if it does not. > and the act of detecting which slit the photon could go through, if it were a particle The whole point of the double slit experiment is that there is only one photon, and which slit it goes through is irrelevant. Whether a photon is a wave-function is missing t…
This reminds me of a passage from Dune.
“Deep in the human unconscious is a pervasive need for a logical universe that makes sense. But the real universe is always one step beyond logic.”
Re: A wave function does not collapse upon detection?
#44Contrary to what used to be hammered into people, it must be observed by the observer, that is, by you. Any random interaction will not trigger the collapse. An interaction must itself be observed by the observer, otherwise it will not cause a collapse. It seems that the universe works pretty much as Haskell does. Things that don't matter to anything else do not happen.
Umm.. no, the observer need not be conscious.
Re: A wave function does not collapse upon detection?
#45Does anyone have a link to a real world example of the double slit experiment where the photons are observed at the slits , causing the wave function of the light to collapse so the light acts as a particle beyond the slit, ending up in two piles on the detector screen, rather than the wave pattern. Every time I ask this, some do-gooder will not read a word I wrote and send me a video of the basic slit experiment and…
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Re: A wave function does not collapse upon detection?
#46> But surely the wave function is smeared across both slits That's the whole point of the experiment - you can't get an interference pattern if it does not. > and the act of detecting which slit the photon could go through, if it were a particle The whole point of the double slit experiment is that there is only one photon, and which slit it goes through is irrelevant. Whether a photon is a wave-function is missing t…
Your answer is the honest answer. We don't know. The physical reality of wave functions is unknown. It could be an approximation of something yet deeper. The only thing we know is that the math works.
Is there a leading theory as to what the physical reality is?
Re: A wave function does not collapse upon detection?
#47Contrary to what used to be hammered into people, it must be observed by the observer, that is, by you. Any random interaction will not trigger the collapse. An interaction must itself be observed by the observer, otherwise it will not cause a collapse. It seems that the universe works pretty much as Haskell does. Things that don't matter to anything else do not happen.
Umm.. no, the observer need not be conscious.
It has nothing to do with consciousness, but the event must matter, or it doesn't happen. Even your consciousness only exist if it matters and will be observed.
Re: A wave function does not collapse upon detection?
#48Earlier quoted context omitted.
I think the most reasonable explanation is that unobserved things do not happen, at all, or only happen on some abstract statistical level. That doesn't imply that consciousness is special. The reason why you are aware of reading this, if you are indeed aware of reading this, is that your life matters for some future event, which on the fundamental physical level has already happened, but its exact results depends on…
What's that "meow" sound I hear coming from that box over there?
That's an observation.
Schrodinger cat isn't both dead and alive. Nothing happens in the box while it's closed.
Really think about how this is an elegant solution that makes it completely un-paradoxical, excluding that events happen out of order compared to our intuition.
Re: A wave function does not collapse upon detection?
#49Earlier quoted context omitted.
The notion of the wave function collapse is very specific to Copenhagen interpretation of quantum mechanics that tries to reconcile classical and quantum world. But everything is quantum so there is no classical measurement device, just its wave function interacting according to fully deterministic equations with the wave function of the electron. The catch is that appearance of classical objects is still unsolved pr…
> The catch is that appearance of classical objects is still unsolved problem in QM. What? Decoherence explains classical objects.
Classical objects are not explained in Quantum Mechanics, they are a fundamental part of the theory itself. (Measurement is an interaction with an apparatus which is a classical object.)
Re: A wave function does not collapse upon detection?
#50Earlier quoted context omitted.
> The catch is that appearance of classical objects is still unsolved problem in QM. What? Decoherence explains classical objects.
No, it doesn't. Decoherence explains why self-interference of a single wave-function doesn't happen after interaction with the environment. But it doesn't explain two important things. 1, which is very practical, is that it doesn't explain why the wave function always decoheres in the same way. In experiments, you can always chose the basis of measurement, and get some definite results in that particular basis, while…
The many worlds interpretation works better with quantized probability. Imagine a huge computer running a monte carlo simulation with a probabilistic current state, and a set of transition states (the wave function). With quantized probability and a universe with finite "memory" the amplitude of the wave function basically maps to the amount of system memory being utilized for a portion of the simulated state space.