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Physicists found a new quantum paradox that casts doubt on a pillar of reality

sciencealert.com

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Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality

#81

Post by elwell »

c1ccccc1 wrote: post #59
amelius wrote: post #8

Earlier quoted context omitted.

Nice video. Now I wonder if God uses structurally shared data structures in his implementation of the world. I also wonder if there can be a kind of continuous description of branching that is more amenable to calculus than the discrete tree-like branching.

I think MWI actually predicts continuous branching. The prescription for MWI is just to run the Schrodinger equation forwards in time. So the branching would look like one blob of probability gradually becoming bimodal, and then splitting into two components with less and less overlap. (There might also be 3-or-more-way branches, not just binary splits.)

Tell me about the 'superworld' that hosts the many worlds.

Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality

#82

Post by tsimionescu »

elwell wrote: post #79
tsimionescu wrote: post #73

Earlier quoted context omitted.

You may say that it's not surprising, but in fact all statistical-style reasoning relies on it. If the universe is superdeterministic, than no kind of statistical reasoning makes any sense, since everything is already set in stone, there is no probability to any event, it has either happened already or will never happen. Since there is no freedom or even randomness, there are no statistically independent events or me…

> no kind of statistical reasoning makes any sense Probabilities are useful when you don't have perfect knowledge . But yes, they are an illusion. In truth, every event has a 100% chance of happening. And things that didn't happen aren't real events, they just seemed to be possible, but we were wrong.

Sure, but please stop requiring clinical trials for new medicine, as they have no more relevance than throwing a coin. Oh, and stop throwing coins, as the result is correlated with the future decision which you will take anyway.

In general, all of modern science, starting with quantum mechanics, depends on the idea that statistical independence exists. To truly abandon this idea, we would abandon almost all of the mathematical apparatus that has given us QM and all experimental observations of QM.

Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality

#83

Post by rightbyte »

phkahler wrote: post #27
canjobear wrote: post #20

Earlier 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…

I always thought Schoedingers cat should have been a person instead, just to point out this very problem.

Schrödinger's cat was also supposed to show a paradox not be a cool quantum magic physics thing.

Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality

#84

Post by elwell »

katmannthree wrote: post #48
08-15 wrote: post #35

> 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. [1]: https://www.youtube.com/watch?v=ihhVe8dKNSA

The members of a system can 'experience' free will from their perspective, but it's a still a deterministic line of causation; their free will is part of the determinism.

Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality

#85

Post by hggfkkbcfd »

One this I always notice to be missing from discussions of quantum physics is the effect of scale. Does differences scale have relativistic effects, in a similar manner to differences in internal frames, and if at what do events in one scale frame of reference become simultaneous of an observer in another?

Note: IANAP

Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality

#86

Post by elwell »

tsimionescu wrote: post #82
elwell wrote: post #79

Earlier quoted context omitted.

> no kind of statistical reasoning makes any sense Probabilities are useful when you don't have perfect knowledge . But yes, they are an illusion. In truth, every event has a 100% chance of happening. And things that didn't happen aren't real events, they just seemed to be possible, but we were wrong.

Sure, but please stop requiring clinical trials for new medicine, as they have no more relevance than throwing a coin. Oh, and stop throwing coins, as the result is correlated with the future decision which you will take anyway. In general, all of modern science, starting with quantum mechanics, depends on the idea that statistical independence exists. To truly abandon this idea, we would abandon almost all of the ma…

No principal investigator of a clinical trial has perfect knowledge of the current state of reality, nor the means to calculate subsequent states. Therefore statistics are very useful.

Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality

#87

Post by Strilanc »

The article lists three assumptions that one might intuitively think hold. The problematic assumption is this one:

> When someone observes an event happening, it really happened.

Given the experiment from the paper, I would rephrase this assumption as "it's not possible to rewind things". But obviously inside a computer simulation made up of operations that are all individually reversible, it's trivial to rewind things.

The experiment sets up a situation where certain information is reversibly recorded, and then the records are unmade by temporarily rewinding. The rewinding is obfuscated by hiding it inside of a measurement that is incompatible with the presence or absence of the record. I guess the authors might disagree about the measurement implying rewinding, but as a bit of evidence I'll note that Scott Aaronson and Yosi Atia have shown that performing the measurement in question over a simulated agent is at least as expensive as rewinding the simulated agent [1]. Whatever is being done, it is doing some seriously expensive screwing around with the agent's state. It's like the experiment has a step where you feed the human through a giant meat processing plant, and for some reason everyone is pretending that's not somehow important.

Basically, the authors are appealing to the intuition that humans are big complicated in-practice-irreversible things, so clearly a record is permanent if it has affected the state of a human. But then they imagine instantiating the human's state inside a ridiculously powerful computer capable of reversibly simulating time advancing and of performing operations that have been engineered specifically to mess with the presence or absence of the record's effects on the human's state. Surprise surprise, the record gets messed with. Then for the actual experiment the big complicated ball of dependent spaghetti that is a human is replaced by a nice simple photon going along one path or another path.

1: https://www.scottaaronson.com/blog/?p=4786

Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality

#88

Post by tsimionescu »

elwell wrote: post #86
tsimionescu wrote: post #82

Earlier quoted context omitted.

Sure, but please stop requiring clinical trials for new medicine, as they have no more relevance than throwing a coin. Oh, and stop throwing coins, as the result is correlated with the future decision which you will take anyway. In general, all of modern science, starting with quantum mechanics, depends on the idea that statistical independence exists. To truly abandon this idea, we would abandon almost all of the ma…

No principal investigator of a clinical trial has perfect knowledge of the current state of reality, nor the means to calculate subsequent states. Therefore statistics are very useful.

They may or may not have perfect knowledge, but if they don't have free will or any ability to randomly choose participants, then there is no reason to trust that the patients they choose are not correlated to the medicine they are testing, such that all of the patients they chose will have the maximum response possible to the medicine, with the least amount of side effects.

Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality

#89

Post by robocat »

lisper wrote: post #30

> 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…

> No AI can run on a quantum computer

Each quantum calculation can be collapsed to a state, and that state could then be fed to the next quantum calculation etc. etc.

Would you call a series of such quantum calculations a quantum computer, or not?

Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality

#90

Post by Strilanc »

lisper wrote: post #72
Strilanc wrote: post #65

Earlier quoted context omitted.

Requiring the the quantum algorithm have literally no interaction with the outside world to count as quantum is a strawman. An AI could use Grover search when trying to find a good enough response. That would be like part of the AI going into and out of superposition for an efficiency boost. Many quantum tasks are more efficient if certain catalyst states are present [1][2]. That would be like a part of the AI stayin…

Let's not lose the plot here: we're talking about a Wigner's-friend-type thought experiment. If you're not going to require that the quantum computer be isolated, then you may just as well use an actual human.

Agreed. The measurement at the end of the experiment requires the agent's state to stay under superposition with no leaks (or perhaps only trivial leaks that can be patched over).
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