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Experiments spell doom for physical-collapse explanation of quantum weirdness

quantamagazine.org

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Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#141

Post by pdonis »

whimsicalism wrote: post #136
pdonis wrote: post #113

Earlier quoted context omitted.

> You can derive if from the MWI. Not as an actual physical process, no. "Collapse" in the MWI just means that, once the "worlds" have decohered, within each "world" the wave function can be collapsed to the one that describes the measurement result observed in that "world", for purposes of predicting future results. But in the MWI this is just a mathematical convenience and doesn't correspond to anything physically…

> doesn't correspond to anything physically happening It corresponds to the inner product of the two branches of the wavefunction going to 0 due to physical phenomenon.

That is decoherence, not collapse. Collapse, as a physical process, would be all of the branches but one ceasing to exist.

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#143

Post by GoblinSlayer »

naasking wrote: post #106
GoblinSlayer wrote: post #100

Earlier quoted context omitted.

Discovery of non-linearity in the evolution operator would falsify MWI. Like e.g. this germanium experiment gave a positive result.

Yes, because it falsifies every interpretation of quantum mechanics not just MWI itself. I think in context here, "is superdeterminism falsifiable" is as silly a question as "is logic falsifiable" or "is causality falsifiable". Specific mmathematical, causal or superdeterministic models are always falsifiable, but the idea that superdeterminism as a whole is not falsifiable should be no more surprising or interesting…

If superdeterminism allows specific models. The idea is that the experimenter's behavior is fine tuned so he can't discover superdeterminism, which means falsification would be a paradox by definition.

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#144

Post by jfengel »

mjan22640 wrote: post #124
jfengel wrote: post #92

Earlier quoted context omitted.

That's right: the "collapse" interpretation is an approximation. You can derive if from the MWI. We already know that the "worlds" separate and almost completely cease interacting. The interactions decrease to the order of "two to the power of Avogadro's number" almost immediately. The collapse interpretation rounds that to zero (at some arbitrary point). To make that more concrete you have to add a term to the equat…

Could the other branches be our dark matter?

No. They don't behave at all like dark matter. Among other things, there's no reason for them to be distributed in a halo, nor for some galaxies to lack them.

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#145

Post by whimsicalism »

causi wrote: post #57
ThalesX wrote: post #6

Earlier quoted context omitted.

Having been passionate about this for awhile, I have a layman’s surface overview of the state of physics, or I like to believe so. It amused me to no end when my elderly aunt came to ask me for a tl;dr; on Quantum Physics. She stopped me shortly asking how she can control the universe with her mind. I tried to explain a bit about the famous interpretation (Copenhagen, not Von Neumann–Wigner) but she would have none o…

What I don't understand is why we call it "observation" when it should really be "interaction". The quantum weirdness resulting from the collapse of probabilities has nothing to do with a conscious observer, just whether and at what point the phenomena in question interact with something else in an observable way.

Because when an object "interacts" with another object, it goes into a quantum superposition with that object. It is only when we observe that we don't see the superposition.

The obvious implication that people don't like to talk about is that there is nothing special about observation, it is just that our own body goes into superposition and we only subjectively experience one of the quantum states.

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#146

Post by tshaddox »

ffhhj wrote: post #97
tshaddox wrote: post #88

Earlier quoted context omitted.

David Deutsch seems to think that a general intelligence running on a quantum computer ought to be able to observe itself existing in parallel worlds if many-worlds is true.

> observe itself existing in parallel worlds if many-worlds is true If many-worlds is true, we are already observing ourselves in each of those universes in which we can observe, we just don't communicate with our replicas. And if the AGI can communicate with its other instances, the exponential replicas will quickly overload their channel.

I think the point of the claim is that a general intelligence running on a quantum computer would make different observations if many worlds is true versus if many worlds is false.

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#147

Post by tshaddox »

xwolfi wrote: post #93
tshaddox wrote: post #88

Earlier quoted context omitted.

David Deutsch seems to think that a general intelligence running on a quantum computer ought to be able to observe itself existing in parallel worlds if many-worlds is true.

Which sadly means nothing, so many details being hidden behind the words "general", "intelligence", "running", "quantum computer", "ought", "oberve" and "existing". If you could refine what these words all mean, I guess we could understand it as something more than "Deutsch seems to think that yes", which can replace your sentence entirely, "yes" describing it all as precisely. I am myself, in some ways, a general in…

Most of those words don’t cause definitional problems here any more than they do for all other scientific tests which involve general intelligences (humans) making observations about things that exist. “Quantum computer” is a unique term that doesn’t show up in every description of a scientific experiment, but as far as I know it doesn’t have a particularly ambiguous definition.

And while you are indeed a general intelligence, I don’t think you’re running on a quantum computer.

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#148

Post by tshaddox »

naasking wrote: post #89
tshaddox wrote: post #88

Earlier quoted context omitted.

David Deutsch seems to think that a general intelligence running on a quantum computer ought to be able to observe itself existing in parallel worlds if many-worlds is true.

I'm skeptical that Deutsch actually meant that, but even smart people have crazy ideas.

He wrote a pretty well known article about it that as far as I can tell wasn’t written off-hand and hasn’t been retracted or disavowed. I’m pretty confident he meant it.

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#149

Post by whimsicalism »

tsimionescu wrote: post #122
telmo wrote: post #52

Earlier quoted context omitted.

I also prefer the Many Worlds interpretation and I do think that it is gaining popularity in relation to Copenhagen, but I'm not sure what you mean by "today's world view". And who is this "we" that you write about? I prefer Many Worlds because it is a simpler explanation, so I follow Occam's razor. That's it. Consciousness and the existence of qualia remains a fundamental mystery. There is something definitely speci…

MWI is exactly as simple mathematically as CI, so not sure what you mean by "simpler". MWI still postulates the equivalent of wave function collapse, but instead of it happening only for the quantum system being measured, it is happening in the mind of the observer, as each "version" of that mind gets entangled with a single "version" of the outcome. Even if you were to accept that this process is more natural (so no…

> you then need to recover the relationship between the probability of observing a certain outcome and the amplitude of that outcome in the wave-function.

I have never understood how that is a strong objection. We've experimentally determined that the state you are more likely to find yourself in is based on the squared amplitude. How is this different from CI but with probability of observing given state - which was also determined empirically?

> Of course "measurement apparatus prepared in a certain basis" does a lot of work here, as we don't know how to define this in terms of a quantum system.

Yes, this is where the Occam's razor bit comes in.

> So, the MWI has to actually introduce extra elements (the worlds and their number, and the observer wanting to compute a probability) to explain the actual measured results of quantum experiments.

The worlds and their number are equivalent to the states & probability of CI without having to introduce the "measurement apparatus" that is distinct from the quantum system.

Re: Experiments spell doom for physical-collapse explanation of quantum weirdness

#150

Post by whimsicalism »

pdonis wrote: post #141
whimsicalism wrote: post #136

Earlier quoted context omitted.

> doesn't correspond to anything physically happening It corresponds to the inner product of the two branches of the wavefunction going to 0 due to physical phenomenon.

That is decoherence, not collapse. Collapse, as a physical process, would be all of the branches but one ceasing to exist.

Oh I misread your comment - I thought you were referring to decoherence as the mathematical convenience. Now that I see that it was collapse, definitely agree.
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