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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

#141

Post by dkersten »

abetusk wrote: post #58
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 is incorrect. What you've described is classical correlation, not quantum correlation.

Would this be correct:

You take a marble out of the bag without looking and give the bag to your friend. Your friend also take a marble out of the bag without looking. Both you and your friend now look at your marbles and they will both be the same colour every time.

You can't send information this way because you don't know the colour until your friend has already taken a marble too. You cannot do anything with the fact that they are both the same colour unless you can control or know the colour in advance, which you can't. When you look at your marble and see that its red, your friend looks at their marble and sees that its red, all you know is you both have red marbles.

The only way to send information would be if you took multiple marbles, looked at them until you found one that's blue (say, the third) and then told your friend to look at the third marble. But since you can't tell your friend to do that without using traditional information sending, you may as well just tell them that the third marble is blue and forego the marbles altogether, you're not sending faster than light information anymore anyway.

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

#142

Post by dragonwriter »

feoren wrote: post #139
tbabb wrote: post #91

Earlier quoted context omitted.

> 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 quantu…

My understanding is that "Wave function collapse" is an artifact of one of the many possible ways of describing quantum mechanics mathematically. There's really nothing to remove, is there?

> My understanding is that "Wave function collapse" is an artifact of one of the many possible ways of describing quantum mechanics mathematically.

The contention seems to be that the Copenhagen interpretation elevates wave function collapse from mathematical artifact to real phenomenon.

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

#143

Post by lisper »

gus_massa wrote: post #122
lisper wrote: post #82

Earlier quoted context omitted.

See section 4.2, and in particular the paragraph that starts "Here's the kicker..." It is true that you can't tell if a single particle is entangled or not. But if you have an ensemble of particles all prepared in the same state then you can tell if that state is entangled or not. Non-entangled (a.k.a. pure) states have a preferred basis that produce self-interference. Entangled (a.k.a.) mixed states do not. (The pur…

I agree with the GP. If you only have a single member of the pair, then you will see the same interference pattern in a double slit experiment than with a not-entangled particle. It doesn't matter if the other particle has collided with a brick, went thru a double slit experiment, went thru a bad double slit experiment, or is flying to Andromeda. (In spite that the calculation to get the correlation with any result i…

What can I say? You're wrong. The math shows that you're wrong (as does the elementary argument presented in the paper). Find a physicist and ask them if you don't believe me.

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

#144

Post by UncleOxidant »

naasking wrote: post #126
UncleOxidant wrote: post #124

Earlier quoted context omitted.

It's kind of interesting how people who would never consider a creationist explanation seem quite willing to embrace the idea that we're in a simulation.

One is an assertion with no logic to justify it, the other is an assertion with a somewhat persuasive argument justifying it [1]. They are simply incomparable. [1] https://www.simulation-argument.com/simulation.html

But how is the simulation hypothesis not positing a "god" of some sort (some kind of super-intelligence that they claim is behind it all)? It seems like the simulation hypothesis is a theistic hypothesis. Or do they assume the simulation just evolved?

Also, why the assumption that post-humans are running the simulations (as in the paper)? Couldn't it be any ultra-advanced civilization that's playing with an evolutionary simulation?

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

#145

Post by serverholic »

Kranar wrote: post #66
tylerhou wrote: post #56

Earlier quoted context omitted.

> Rather, both balls are in a superposition of being both red and blue simultaneously, and it is not possible in principle to assign a color to either one of them until the moment a measurement is made. I don't disagree, and (clearly) I make a measurement when I show you the color of a ball. Before I show you a ball, I would also say that the colors of the balls are in a superposition. > major revolution in physics i…

Fair enough we'll simply disagree on that. Entanglement is not a property about wave functions and really has nothing to do with waves. It's a logical consequence of the uncertainty principle and was ironically deduced by Einstein, Rosen, and Podolsky (EPR Paradox) as a way to argue that quantum mechanics is an incomplete description of physical reality. Being that it's strictly a consequence of the uncertainty princ…

I think you're having a pedantic moment. Nobody claimed that the red/blue ball example was some big unsolved mystery. It's merely to give people a taste of entanglement in a way that your average person can understand.

Isn't it true that if you entangle two particles, separate them, then measure one it'll tell you something about the other particle? That's all the example is trying to communicate.

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

#146

Post by serverholic »

lisper wrote: post #40
tylerhou wrote: post #33

Earlier quoted context omitted.

> it suggest that it’s just a matter of a hidden variable. I disagree. Suppose that I create a machine that chooses which ball to place in each box. This machine makes the choice based on some measurement of a quantum particle (electron spin). Then the colors of the ball are entangled with the state of the quantum particle, which cannot be described by some local hidden variable.

Only if you can completely isolate the balls so their states don't decohere. That is not practically possible to achieve, particularly since in your scenario you reach into the bag and touch the balls. As soon as you interact with the balls in any way, you become entangled with them and the behavior of the system becomes classical.

You didn't add anything to his example. This is just purely to be pedantic.

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

#147

Post by UncleOxidant »

feoren wrote: post #135
naasking wrote: post #126

Earlier quoted context omitted.

One is an assertion with no logic to justify it, the other is an assertion with a somewhat persuasive argument justifying it [1]. They are simply incomparable. [1] https://www.simulation-argument.com/simulation.html

Of the 3 assertions in the abstract, the obviously false one is #2: "Any posthuman civilization is extremely unlikely to run a significant number of simulations of their evolutionary history". When you realize that running a simulation of the universe requires more processing power than is available in the universe, this is very obviously false. I respect people who believe in a bearded White omnipotent homophobic Go…

The simulation hypothesis seems as theistic as the creationist hypothesis. Maybe the main difference being that with the simulation there would likely have been many creators (programmers) whereas the creationists would say there is one (although there are polytheistic creation narratives, so maybe not so different). Other than that, they both seem to fall into the theistic category since a higher intelligence is posited who created (the simulation | the real world).

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

#148

Post by lazide »

feoren wrote: post #130
Kranar wrote: post #66

Earlier quoted context omitted.

Fair enough we'll simply disagree on that. Entanglement is not a property about wave functions and really has nothing to do with waves. It's a logical consequence of the uncertainty principle and was ironically deduced by Einstein, Rosen, and Podolsky (EPR Paradox) as a way to argue that quantum mechanics is an incomplete description of physical reality. Being that it's strictly a consequence of the uncertainty princ…

While I believe that entanglement is genuinely something new and interesting, your explanation of it simply feels like a semantic difference. There is no way in which the universe you describe would be different from a classical universe, at least up to the limits of your description. I'm simply "not allowed" to say that one of the balls is red and the other is blue, before I've looked? It's just, what, against the l…

Ah, but that’s the tough part - there IS a measurable difference in behavior of the universe between these two examples! (albeit hard to experimentally prove exists, but it has been!)

They really are in a superposition, not just ‘not known’ until one is measured.

Just like light was proven to (truly, actually) be both a light and a wave through the double slit experiments. It doesn’t feel right, but it is - and that is where the progress is made, and why the pushback on some examples. It hides the actual truth behind a misleading, but easy to understand example, that teaches people the opposite of what is really going on.

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

#149

Post by serverholic »

feoren wrote: post #135
naasking wrote: post #126

Earlier quoted context omitted.

One is an assertion with no logic to justify it, the other is an assertion with a somewhat persuasive argument justifying it [1]. They are simply incomparable. [1] https://www.simulation-argument.com/simulation.html

Of the 3 assertions in the abstract, the obviously false one is #2: "Any posthuman civilization is extremely unlikely to run a significant number of simulations of their evolutionary history". When you realize that running a simulation of the universe requires more processing power than is available in the universe, this is very obviously false. I respect people who believe in a bearded White omnipotent homophobic Go…

Isn't it possible that our universe is really just an approximation meant to look as detailed as possible? You don't need a universe of processing power to simulate a universe. You just need to make it look believable enough that it fools whoever is in your simulation.

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

#150

Post by Kranar »

serverholic wrote: post #145
Kranar wrote: post #66

Earlier quoted context omitted.

Fair enough we'll simply disagree on that. Entanglement is not a property about wave functions and really has nothing to do with waves. It's a logical consequence of the uncertainty principle and was ironically deduced by Einstein, Rosen, and Podolsky (EPR Paradox) as a way to argue that quantum mechanics is an incomplete description of physical reality. Being that it's strictly a consequence of the uncertainty princ…

I think you're having a pedantic moment. Nobody claimed that the red/blue ball example was some big unsolved mystery. It's merely to give people a taste of entanglement in a way that your average person can understand. Isn't it true that if you entangle two particles, separate them, then measure one it'll tell you something about the other particle? That's all the example is trying to communicate.

>Isn't it true that if you entangle two particles, separate them, then measure one it'll tell you something about the other particle?

Yes that's true, but that's also true of things that aren't entangled. I assure you if I went to Socrates, showed him a red ball and a blue ball, put them in a bag, and took out a ball at random that happened to be red, Socrates would have no problem realizing that the other ball must be blue. I am sure if I went to my 4 year old daughter, she'd figure it out as well because nothing about quantum mechanics or entanglement would be needed to understand this.

What entanglement tells us is that if two balls had their colors entangled, then both balls are both red and blue at the same time and it's simply not possible to reason about one ball being blue and one ball being red while they are entangled. They are in a superposition of both colors and remain so until a measurement is performed.

Once the measurement is performed, they are no longer entangled and only at that point can you call one ball red and the other blue.

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