/sci/ - Science & Math

https://phys.libretexts.org/Bookshelves/Quantum_Mechanics/Quantum_Mechanics_III_(Chong)/03%3A_Quantum_Entanglement/3.04%3A_Bell's_Theorem

>>15103947
https://youtu.be/ZuvK-od647c?t=4m44s

>>15103947
>Can someone explain how is this a paradox of physics that somehow got Einstein's jimmies rustled
according to the Copenhagen interpretation. the objects are in a superposition until the moment their state is measured and it registers in the mind of a conscious observer.

>>15103954
>>15103974
simple classical systems violate Bells inequality

>>15103988
>>15103992
This guy is a well-known schizo. Do not argue.

Nobel prizes are bullshit

>i'm gooooooonnnnaa quantooooooommmmmm!!!!
>my science is so small that nobody can see it
>hahaha can't prove me wrong if you can't see it
>i fucking love science!!!!!

>>15104003
>This guy is a well-known schizo. Do not argue.
why? you know you can't win?

>>15103947
The difference is in your balls example, the balls "already" have a color, even before we open the box, classically speaking.

But a quantum-mechanical particle does NOT have a definite spin (or position, etc, whatever's being measured), until the measurement/observation takes place.

>>15103947
It's because of Bell's inequality. It is mathematically impossible to simulate the correlations between measurement outcomes you see in quantum mechanics using something like boxes with balls. The correlations are such that there HAS TO be some way of superluminally influencing one particle by the other.
>Bell showed, however, that such models can only reproduce the singlet correlations when Alice and Bob make measurements on the same axis or on perpendicular axes. As soon as other angles between their axes are allowed, local hidden-variable theories become unable to reproduce the quantum mechanical correlations.
The "problem" appears when two people measure at different locations using randomly chosen measurement settings (angles) and you assume the random choice of these angles are themselves unrelated.

>>15104154
>. It is mathematically impossible to simulate the correlations between measurement outcomes you see in quantum mechanics using something like boxes with balls
Explain >>15103992 then. The reality is it is possible. Many simple classical local and real systems violate Bells inequality. What happens is these solutions are dismissed as loopholes without any real justification.

>>15104154

>>15103947
because with the model soi physcis uses there isnt supposed to be any medium for which to communicate information through to tell it which state to exhibit

>>15103947
>>You have one red ball and one green ball
>>Leave the room while friend put each ball in its own box and tape it shut
>>Shoot one box in a ball into space and wait until it reaches one light-year
>>Open box that stayed on Earth and see red ball
>>Instantly knows other ball is green
>>"Uhhhh.....spooky?!?"
btw this isnt an accurate analogy. Both are in superposition before you look. One isnt already "red" therefore the other is "green." It happens instantaneously

>>15104208
>Both are in superposition before you look
That's just your interpretation. Ops is just as valid
>Bell
No one ever proved free will exists, so it's not necessarily even true

>>15104117
>>15104208
>interpreting statistical modelling as conceptual fact
Wave functions are just a useful mathematical description. Particles have a definite state at any given instant, but because the states are so sensitive to perturbation one cannot know what its particular state is at a given moment unless it interacts with something. Entangling particles through some quantifiable interaction and then measuring the state of one only lets you know the state of the other after that initial interaction.

I also think this one is useful
https://physics.stackexchange.com/questions/128848/why-would-classical-correlation-in-bells-experiment-be-a-linear-function-of-ang
Key points are the linear/cosine graph in the question, and the 2nd answer which gives a simpler but sufficient variation:
>Bell proved an over-general result that is unnecessarily hard to understand. You don't need a continuum of measurement angles to get a nonclassical result, just three. With three angles, the argument above shows that there are only 23=8 possible "answer strategies" for the boxes, which we can write UUU, UUD, UDU, ..., DDD (where U means the first box says "up" and the second "down", and D is the reverse). Two of those, UUU and DDD, lead to the boxes always disagreeing. The other six are all equivalent under permutations and exchange of U and D, and they lead to the boxes agreeing 2/3 of the time when the angles are different. So 2/3 agreement is the highest possible in a classical world. But in a quantum world, measuring Bell-pair electrons along axes of 0°, 120° and 240° gives agreement 3/4 of the time.

>>15104445
>No discussion of the assumption that humans have free will.

Entanglement fans won't acknowledge these facts
1. Bells inequality is predicated on the idea humans have free will
2. Classical systems violate bells inequality but are unjustly dismissed as "loop-holes"
3. Classically light is a wave not particle, so the "classical predictions" made by entanglement fans are nonsense

>>15103988
OP here. So, if someone at a distance measures an entangled particle's state and get one state, then someone on the other end should also see some change in the other entangled particle indicating that it's no longer in superposition, right?

>>15104677
>someone on the other end should also see some change in the other entangled particle indicating that it's no longer in superposition, right?
no. thats not part of it.

>>15103988
We can shed the metaphysical nonsense. That's just a fancy way of saying "you don't know until you look."

>>15104677
I just wanna chime in here and hopefully clarify the whole thing OP

The Copenhagen interpretation implies the particles exist in superpositions of states that collapse upon measurement. To be specific, this means the natural state for quantum particles is a superposition of all possibilities. Mathematically, we represent an unmeasured particle as a superposition function which shows us the probability of a particle being measured with any given value of any given property. This means we have a graph of x, y, and probability all plotted on their own axis (or you may say, as their own dimension!).
I want you to now imagine the probability function as an actual property of the particle, like mass or charge, or x-position. When we measure the particle's momentum, and 'collapse this wave function', mathematically we are performing a Fourier transform on the probability (or wave) function. This means we are taking information about a function and projecting it into another dimension. In normal math, this would be the frequency dimension, but in quantum mechanics we transform the wave into a new function in 'momentum space'! The Copenhagen interpretation says we have fundamentally altered this particle by transforming the wave function.

Now that a particle was measured, and the wave function collapsed: we can perform experiments with this particle and predict the outcome 100% of the time. We have altered the state of the particle by measuring it; no longer is a superposition.

An entangled pair means (mathematically) that we can describe both particles with a single wave function; imagine two sine waves, summed. Therefore, by measuring one particle, you have actually measured both and (spooky action:) collapsed both wave functions! You have influenced the entangled counterpart as if the information traveled faster than light - telling the distant particle to now exist with a collapsed wave function.
However, information itself is still capped at c.

>>15104677
>>15105305
>However, information itself is still capped at c.
I just want to clarify:
Here I am saying you now know something about that very distant particle, so what can you do?
Well nothing.
Sure, you know something about it, but the only way to act on that knowledge is to convey information about the particle to the location that other particle exists at. For instance, maybe you send an electrical signal to the particle, or maybe you send light rays which communicate information to another lab team; it doesn't matter.
That information you send is capped at the speed of light. Therefore, although something is happening faster than light, no information has traveled faster than light.

>>15104200

>>15105314

>>15105393
>>15105664

>>15105393
>>15105664
l

>>15103947
It's not spooky if you think of the 'particles' as data objects and realize that space is virtual and all points are equidistant to the processor and it's an if then situation, if spin up, then spin down, for instance. It's only spooky if you are a physicalist who believes that matter is objective/ observer independent and fundamental. If you look at matter as part of a set of relatively correspondent subjective data streams emergent in/rendered to mind/s, then it makes perfect sense.

>>15104208
>Both are in superposition before you look.
No they're not, the outcome is already determined when one of the balls is put into a box

>>15107132
Hidden variable has been experimentally disproven

>>15107171
>Hidden variable has been experimentally disproven
no. read this and address even one (1) point >>15104565

>>15103947
I can say that for the double slit eraser experiments, entanglement just refers to two photons created at exactly the same time.

All other forms of entanglement discussion not involving laser light beams is purely hypothetical. On the level of staring at a goat to kill it.

>>15105305
I'm a tard, so I'm confused. If you can know something about the other particle isn't that technically information communicated from light euars away instantly therefor faster than c. Couldn't this be used to like... Communicate between two people very far distances instantly if you changed the particles in a way that can be read like binary more code? So you have like a trillion entangled particles then you just go across each one and either measure and collapse each one or not thus binary thus a language limited in characters to the number of particles

>>15107193
Yes and No, and trust me this isn't designed to be intuitive. I'll try to be brief as it appears some retard thinks the complexity of my speech in a simplified explanation is directly correlated to a low IQ (>>15105664) and now I remember why I stopped posting here so long ago.
In the spirit of low IQ explanations I will try to make this simple.

You ask, "was information sent faster than light?" And you must know the answer is no. Although we (I'm assuming we measured the entangled pair) have collapsed the wave function and fundamentally altered the state of the distant particle - the other lab team has no idea.
There is no way of knowing that this particle is no longer fundamentally random, unless they, too measure their particle.

You must also understand that this 'entanglement' isn't magic and is actually extremely fragile. When we say we can describe two entangled particles with the same wave function, we don't usually include: it only works if each entangled counterpart stays completely isolated from all outside factors. We cannot 'poke' our particle and expect an equal and opposite anti-poke to happen to the entangled counterpart. That's not how it works. There is no spacetime bridge between these particles! In fact, you can argue that perhaps nothing has happened at all! You must realize that the Copenhagen interpretation is simply an attempt to make quantum mechanics more intuitive. Nothing more. We may use language like 'has effected' or 'collapsing the wave function' but these are just words. Truth is, we don't have an intuitive way to understand what's happening. Nothing like it has ever happened in the macroscopic world we perceive. We can only say that we 'collapse a wave function' or etc because that's how the Copenhagen interpretation defines these actions.

In the 'many worlds' theory for instance, the 'collapsing of a wave function' is instead a time-junction where all possibilities play out in an infinite multiverse.

>>15107193
>>15108878
And in the spirit of trying to keep things simple, it appears I've created another max length post which tries to simplify an extremely complex topic and blurs a few details together. Oh boy I can't wait to be called 90IQ again by some Asian micropenis who scans this board all day.

Rather than try to explain further on this horrible website, I'll try something else. Many people have already created fantastic resources to understand these phenomena, but one in particular I have found exceptionally accessible for those who are technically inclined, but perhaps not physicists. That resource is the PBS Spacetime YouTube channel.
I would recommend surveying their catalog and watch their videos simply based on what questions stir in your mind.
I'm sure you'll find their content is fantastic and consistently intuitive. The educator on the channel, Dr. Matthew O'Dowd is extremely well versed in teaching this content and is well aware of how confusing it can be. The entire purpose of the channel is to exist as a resource for those who learn physics and struggle to understand some of the complex ideas that can result. In more recent years, the Dr has opened the channel to some community-based questions, but I assure you that some videos merely a few years old are purely designed to help struggling students and enthusiasts understand this complex field.

>>15107193
>>15108911
start here perhaps, and see where your journey takes you
https://www.youtube.com/watch?v=tafGL02EUOA

>>15108911
thanks man

>>15103947
Ball example is incorrect
Try photons and polarizers
Then try to write a simple program which simulates real experiment.
You will quickly understand that you can't write such program without giving to other photon information what angle of polarizer was used when it was mwasured

Why is wave function collapse such a midwit filter?

>>15104232
>That's just your interpretation.
explain quantum eraser then

>>15104402
unfounded conjecture

I fail to understand how any of this is actually useful in reality. If two particles have correlated properties (due to whaterver the fuck conservation law or whatever) and you measure one of them, aren't you interacting with the measured particle, thus changing it's properties? Why would we expect the other particle's properties to be correlated after you've interacted with the other?

>>15110724
It just is, okay?