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How Bell’s Theorem proved ‘spooky action at a distance’ is real

quantamagazine.org

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Re: How Bell’s Theorem proved ‘spooky action at a distance’ is real

#91

Post by tbabb »

danbruc wrote: post #48
drcode wrote: post #34

Earlier quoted context omitted.

Imagine you have a pouch with a red and a blue marble in it, then take out a marble without looking at it and hand the pouch to a friend. Later, if you look at your marble, you instantly have information about the other marble at a speed greater than the speed of light... but you couldn't use that fact to send a message. The only difference in quantum physics is that there are actually two parallel universes: One in…

The only difference in quantum physics is that there are actually two parallel universes: One in which you took out the red marble & one in which you took the blue one. You don't know what universe you're in until you look at the marble, but still it doesn't help you to transmit a message to your friend. I don't think it is helpful to talk about multiple universes, that makes a strong implication towards a many world…

> that makes a strong implication towards a many world interpretation

You say that like it's a shortcoming. :)

There are many who take the (very reasonable) position that the many worlds interpretation is the most epistemologically parsimonious one. Contrary to some misunderstandings of it, it doesn't "add" extra worlds; it removes the concept of "wave function collapse", and leaves all the other known laws of quantum mechanics completely unchanged. The "worlds" arise naturally as more and more particles in the environment become entangled with the measured system, and "wave function collapse" turns out to be the predicted observation of an observer who is themselves made out of quantum states.

The only difference between many worlds and the "standard" Copenhagen interpretation is that Copenhagen adds that, at some point, the entanglement process stops, and a bunch of states in the wave function disappear. And it doesn't specify how, or why, or how to calculate when it will happen. Those that advocate for many worlds would point out that this extra epistemological burden is questionable, given that the correct prediction is made without it.

Re: How Bell’s Theorem proved ‘spooky action at a distance’ is real

#92

Post by bronzeage »

mensetmanusman wrote: post #84
morpheos137 wrote: post #74

Earlier quoted context omitted.

Personally I prefer the superdeterminism arguement: i.e. the state of every "future" entanglement was already set "before" the big bang. The anthropocentric corollary is that "free will" is an illusion.

The universe seems to have surely went to great lengths to trick its own atoms into believing they have free will. :)

Or maybe you give too much power to free will. Could a Maxwells demon pick the correct timing to close/open the door just by his power of free will? If your answer is yes, then free will can break the second law of thermodynamics. If your answer is no, I will ask, what about in a single small period of time? What is stopping the agent with free will from opening the door then?

I think the same thing prevents Maxwell's demon and a bell observer from having "too much free will", and that thinking of free will in terms of single point in time decisions is also wrong for similar reasons.

Re: How Bell’s Theorem proved ‘spooky action at a distance’ is real

#93

Post by cycomanic »

fnord77 wrote: post #54
drcode wrote: post #34

Earlier quoted context omitted.

Imagine you have a pouch with a red and a blue marble in it, then take out a marble without looking at it and hand the pouch to a friend. Later, if you look at your marble, you instantly have information about the other marble at a speed greater than the speed of light... but you couldn't use that fact to send a message. The only difference in quantum physics is that there are actually two parallel universes: One in…

this seems a little fast and loose. you already had the information the instant you picked the marble, but you didn't observe it until later.

But that's essentially the point. The information is not information until it is observed.

Re: How Bell’s Theorem proved ‘spooky action at a distance’ is real

#94

Post by archibaldJ »

lisper wrote: post #13
ericb wrote: post #3

If we were in a simulation, would the speed of light be the processing speed of the universe as each area re-renders, and spooky action at a distance be two variables pointed to the same memory location, populated with a lazy-loaded value, with copy-on-write semantics? edit: seems like it is lazy loaded, so revised my summary.

That's not a bad analogy, but you have to be very careful here because no classical analogy can be a perfect fit for entanglement. The wave function is deeply and fundamentally different than our classical reality, and there is no way to reproduce its behavior classically. Among the fundamental differences is the fact that classical information can be copied but quantum states cannot be cloned. This is IMHO the singl…

But aren’t these “informations” just representations of (something abstract) reflected in a bunch of quantum states of your neurons? And we humans decide there are homomorphisms between mine and yours and thus they are representing the “same informations”. But really they were fundamentally different. There are no copying. Only some kind of lossy compression mimicking.

Re: How Bell’s Theorem proved ‘spooky action at a distance’ is real

#95

Post by 0majors »

normac2 wrote: post #88
Retric wrote: post #72

Earlier quoted context omitted.

All analogies are flawed because the underlying reality is different. They can still be useful if they can communicate some more abstract idea. An analogy I like for entanglement is to picture two atoms that will both decay at the same time. You could place them on other sides of the planet and until one is observed to decay nobody learns anything because the timing is unpredictable. After the observation people agre…

You describe that as an analogy, but I always took that to be what it actually is (or at least one very simple example). Are you saying that that is how we interpret our experience intuitively, but we need a more radical account under the various mainstream interpretations of quantum physics (Many Worlds, Copenhagen, etc.)?

That’s right. Not only it’s an analogy, it is also a bad one and completely misleading, at least according to physics of the last 50 years. Note how the article frets about the loss of locality.

Re: How Bell’s Theorem proved ‘spooky action at a distance’ is real

#96

Post by tick_tock_tick »

dvt wrote: post #12
ericb wrote: post #3

If we were in a simulation, would the speed of light be the processing speed of the universe as each area re-renders, and spooky action at a distance be two variables pointed to the same memory location, populated with a lazy-loaded value, with copy-on-write semantics? edit: seems like it is lazy loaded, so revised my summary.

If we were in a simulation, it feels overzealous to make the assumption that the computing model would be anything at all like what've developed. Best assumptions you can make is that it follows some kind of consistent logic (though there's caveats here, too).

The speed of light is the exact kinda of constant a programmer would add to a system to solve problems.

Re: How Bell’s Theorem proved ‘spooky action at a distance’ is real

#97

Post by tbabb »

0majors wrote: post #62
drcode wrote: post #34

Earlier quoted context omitted.

Imagine you have a pouch with a red and a blue marble in it, then take out a marble without looking at it and hand the pouch to a friend. Later, if you look at your marble, you instantly have information about the other marble at a speed greater than the speed of light... but you couldn't use that fact to send a message. The only difference in quantum physics is that there are actually two parallel universes: One in…

That’s not quite correct. There are no good analogies between classical objects like marbles or socks and entanglement. In fact, Bell’s inequality was stated as a collaboration game that can only succeed if you use entangled particles. No classical object will get you the same results. You still can’t communicate faster than light but the reason is more subtle. The article does a good job but for a deeper explanation…

I don't think this criticism is correct, at least in response to what was said.

Yes, a classical bag containing classical balls doesn't reproduce quantum behavior, because of Bell's theorem. But GP's description isn't classical; it explicitly invokes multiple universes. Once you've done that, quantum behavior is reproducible, because (just as Bell's theorem says) it's no longer possible to ascribe a single hidden state to the ball/bag system, because you can't eliminate the extra universes.

Re: How Bell’s Theorem proved ‘spooky action at a distance’ is real

#98

Post by zby »

drcode wrote: post #34
nsxwolf wrote: post #27

I'll never understand entanglement. Every explanation makes me wonder why it can't be used to instantaneously send a message. I never fully understand the explanations why it can't be used to do so. I don't understand how you can be sure about the state of the other particle, what if someone already measured it and then did something to it?

Imagine you have a pouch with a red and a blue marble in it, then take out a marble without looking at it and hand the pouch to a friend. Later, if you look at your marble, you instantly have information about the other marble at a speed greater than the speed of light... but you couldn't use that fact to send a message. The only difference in quantum physics is that there are actually two parallel universes: One in…

This marble setup is a 'hidden variable' theory - the article is how quantum is different from that.

Re: How Bell’s Theorem proved ‘spooky action at a distance’ is real

#99

Post by subroutine »

Gunax wrote: post #73

I've been posting this explaination for more than 10 years now: http://www.felderbooks.com/papers/bell.html I think I prefer Felder's explaination more than Quanta's. It's omitting some details (eg. the angles) but is better at explaining the difficulties of Bell's Inequality--why it seems like spooky action at a distance and why it cannot be used for communication.

One thing I've not been able to clarify is whether Bell accounts for the possibility that passing through a polarization filter could effect the waveparticle in some way, like altering its polarization angle.

Re: How Bell’s Theorem proved ‘spooky action at a distance’ is real

#100

Post by eggsby »

wizzwizz4 wrote: post #28
eggsby wrote: post #17

Earlier quoted context omitted.

One reason I often hear astrology is not taken seriously by the scientific community, as in findings like 'athletes often have aries rising on their birth chart' are ignored and not evaluated further, is because there is no empirical foundation for the communication of the effects. https://en.wikipedia.org/wiki/Astrology_and_science

There actually is empirical foundation for the communication of the effects![0] But the model is strictly simpler if you remove the astrology from it; astrology has no additional explanatory power, and its novel claims (claims not predicted by any other model) are wrong. > Such children are more likely to be picked for school teams. Once they are picked, players benefit from more practice, coaching and game time — ad…

Sorry if my language was unclear, I meant to highlight this line from the wiki article:

"There is no proposed mechanism of action by which the positions and motions of stars and planets could affect people and events on Earth in the way astrologers say they do that does not contradict well-understood, basic aspects of biology and physics."

Relevant here because it essentially says "there is no empirical basis for spooky action at a distance" which has been grounds for dismissal of such action-at-a-distance claims like 'the relative positions of celestial bodies influence events on the earth'.

This kind of empiricism has been used as grounds to not critically evaluate these claims. Everyone is certainly free to have their own reasons around why they do not want to evaluate such claims. For example some people only want to consider things that are easily falsifiable and subject to particular scientific practices. The wiki article goes on to mention how Carl Sagan refused to disavow astrology on these grounds (i.e. gravity is weak so stellar influence writ large ought to weak) while still leaving room for a disavowal if it were on firmer grounds. I do think your point about simplicity is salient here.

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