Physicists found a new quantum paradox that casts doubt on a pillar of reality • Hacker News Board

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

#21

Post by jonahbenton » Sun, Aug 30, 2020, 4:22 PM UTC

ssivark wrote: post #14

jonahbenton wrote: post #3

I don't know to what degree the metaphor is accurate but as a non-physicist I find thinking about quantum mechanical experiments easier if I think of them as running code on a vast decentralized computing infrastructure. The concept of "measurement" is just executing code on one node that populates local registers- "creating" not "measuring". Yes- by running code you are pulling on a reality fabric that we still know…

This perspective is interesting and potentially valuable, but it must be emphasized that quantum mechanics has linear evolution and hence “no cloning”. That means, when the registers are quantum objects, there is no such thing as copying a value into a register — there is only one version of each object, and you’re always manipulating it directly. That’s one aspect which leads to very difficult questions when thinkin…

Thanks, understood- the metaphor wasn't intended to imply the registers themselves were quantum objects, more that the process of observation / measurement of some quantum phenomenon- metaphorically- could be a creative/derivative process. That metaphor/mental model would conflict, to some degree, with the centralized/cache coherency metaphor you cite, that aligns more with colloquial understanding of "measure."

Whether one is more appropriate than another I don't know. But I find the decentralized model produces more interesting naive questions for me to puzzle over. Of course those questions likely lead in a completely wrong direction. Cheers, thanks for engagement.

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

#22

Post by jonahbenton » Sun, Aug 30, 2020, 4:24 PM UTC

ahelwer wrote: post #15

jonahbenton wrote: post #3

I don't know to what degree the metaphor is accurate but as a non-physicist I find thinking about quantum mechanical experiments easier if I think of them as running code on a vast decentralized computing infrastructure. The concept of "measurement" is just executing code on one node that populates local registers- "creating" not "measuring". Yes- by running code you are pulling on a reality fabric that we still know…

An alternative way to view measurement is that you're just entangling yourself with the quantum system, and are as much in superposition as the system itself.

Thanks, yeah. With this view I run into trouble understanding what constitutes "entry into" and "exit from" superposition.

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

#23

Post by oopsiforgot7 » Sun, Aug 30, 2020, 4:25 PM UTC

canjobear wrote: post #20

bondarchuk wrote: post #6

The 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…

If you embrace many worlds all these issues go away.

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

#24

Post by ahelwer » Sun, Aug 30, 2020, 4:29 PM UTC

canjobear wrote: post #20

bondarchuk wrote: post #6

The 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…

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.

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

#25

Post by Tuna-Fish » Sun, Aug 30, 2020, 4:35 PM UTC

canjobear wrote: post #20

bondarchuk wrote: post #6

The 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…

Either you believe in collapse, so there are two of you, who each observed different things, and one of those will at some point cease to exist, or you embrace the Everett interpretation, and so there are two of you who each observe different things and go on to live their separate lives.

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

#26

Post by ahelwer » Sun, Aug 30, 2020, 4:37 PM UTC

jonahbenton wrote: post #22

ahelwer wrote: post #15

Earlier quoted context omitted.

An alternative way to view measurement is that you're just entangling yourself with the quantum system, and are as much in superposition as the system itself.

Thanks, yeah. With this view I run into trouble understanding what constitutes "entry into" and "exit from" superposition.

Presumably, nothing was in superposition when the universe began. Everything after that evolved in time according to the Schrodinger equation, with everything becoming more superposed (i.e. their exact properties less certain) and entangled with everything else to at least some degree. Things can be more or less entangled with other things, and when you measure something you become very strongly entangled with it.

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

#27

Post by phkahler » Sun, Aug 30, 2020, 4:38 PM UTC

canjobear wrote: post #20

bondarchuk wrote: post #6

The 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…

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

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

#28

Post by phkahler » Sun, Aug 30, 2020, 4:39 PM UTC

oopsiforgot7 wrote: post #23

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…

If you embrace many worlds all these issues go away.

Or if you embrace nonlocality.

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

#29

Post by guerrilla » Sun, Aug 30, 2020, 4:46 PM UTC

ahelwer wrote: post #24

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…

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.

I'm not convinced it does. Which branch was taken within the box now becomes a local hidden variable so Bell rules this out, no?

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

#30

Post by lisper » Sun, Aug 30, 2020, 4:48 PM UTC

> 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 system and choose to consider only a subset of its degrees of freedom. When you do that, what results is a "mixed state" which behaves classically. This is not a reflection of any (meta)physical reality, it's just a consequence of your point of view. But here's the thing: you yourself are a subset of a quantum system, and so you yourself have no choice but to take this point of view. You cannot ever take the "god's-eye view" and "see" the whole system. That is fundamentally impossible because "seeing" requires copying information, quantum states can't be copied yada yada yada. Even God cannot "see" the god's eye view!