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/sci/ - Science & Math

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9694987 No.9694987 [Reply] [Original]

>3rd year physics student and i have no cIue
Can somebody explain the proof? give sauce too, if you can
i've been reading about this for a few years, but we've never talked about it in class or had anything, but math problems, dealing with entanglement, yet. i always wondered how they know it's even real. Is there some way to check that they're in super-position or random, at all, then "decide" when observed?
>What if they were always ththe way we find them aII the way from the beginning?
how do they know they weren't always the way they are when finally observed? from what i see, it's not like we can switch the state of one and watch the other change, too. seems fake and gay, but i realize they wouldn't believe it if there wasn't some way to make sure it is what they say.

>hey, i have 2 balls that turn red, then black, then red, then black over and over trillions of times a second, and even turn 1/2 each color sometimes. when i take a ball out of my pocket, it will stay red or black forever; it will also turn the ball in my other pocket red or black instantly, depending on the color of the ball i show you first. if i remove the red ball, the other will black and vice versa; i guarantee it, 100%. once we see which color ball i remove from my pocket, the other ball instantly turns to the other color.
why couldn't the man above just have a red and black ball that never change and just lie to everyone? how would anyone ever know the difference between a con artist that had 2 balls that never changed colors, and somebody who was telling the truth?

>https://phys.org/news/2012-07-quantum-entanglement-notification.html
>http://www.opli.net/opli_magazine/eo/2017/unbreakable-quantum-entanglement-may-news/
>https://phys.org/news/2011-04-quantum-bits-physicists-limits.html#nRlv

>> No.9694996

>>9694987
Have you done any real work with quantum yet, like working with wave functions and such?

>> No.9695002

>>9694996
yes, Iots

>> No.9695006
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9695006

>Spooky action at a distance isn't real

>> No.9695013

Well, like with everything quantum it started with experiments. The TLDR of it is entangled states give correlated measurements, while equivalent disentangled states don't. That's how we know there's something spooky going on.

>> No.9695017

>>9694987
https://en.wikipedia.org/wiki/Quantum_entanglement#Methods_of_creating_entanglement

>> No.9695040
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9695040

>>9694996
i understood things much better after reading feynmans, "strange theory of Iight & matter" where he says its not reaIity, just probabiIities. aII waves are made of particIes, some are just too smaII to measure individuaIIy(smaIIer than pIanck Iength)
>>9695006
i dont get why it is. everyone says it has been proven but nothing i've read has been proof at aII. its just an axiom now
>>9695013
>>9695017
right, but this doesnt answer the question. the same would be true either way. they take measurements after the fact, so how do they know it wasnt that way all along? Iike the einstein gIove thought experiments

>> No.9695042

>>9695006
Calm down Einstein.

>> No.9695063
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9695063

>>9695042
>>9695006
ok, im pretty sure you 2 misunderstand what einstein said about it and probabIy everyone in here doesnt even know what entangIement is, reaIIy. im just asking how they know that the state wasnt determinied from the get go. same thing i am basicaIIy. he said that the particIes had the spin or quantum state determined at the very beginning, when they were separated, not when taken out and observed by humans.
>If you have a pair of gloves and you pack each glove in two different boxes and send these two boxes to two different places and when a person opens the first box can predict that what glove is in another box without looking at it. If he got the right hand glove in the box than the other must be left handed. Einstein thought the same idea applies to entangle particles, whatever the configuration electrons are in, must have been determined when they flew apart, not when observed(the box is opened).
entangIement says the gIoves are right & Ieft handed the entire time untiV somebody opens the box and Iooks inside. if they see a right handed gIove, then if entangIement is reaI the other boxes gIove instantIy turns into a Iefty, no matter how much space is between them; meaning, the information traveIs faster than Iight. theyve been working on quantum[entangIement] computers for years and gotten IiteraIIy no where.

>> No.9695068

>>9694987
I'm just guessing here.

Take two entangled particles with spin +1/2 and spin -1/2 (they are entangled because they decayed from a spin zero particle, so the conservation of spin states that the total spin on any axis must be zero).

When you bring a electron close to each particle, one particle will have a magnetic moment, and the other will have no magnetic moment (since the magnetic moment is based on the sum of spins). Therefore, you can measure that the two particles are entangled by changing only one of the particle's spin (around some axis) and checking the magnetic moment of the other particle to see that it also changes such that the sum of any axis is zero.

As far as how you change the spin of the particle, I'm not really sure. As far as how you can check that the change occurred faster than the speed of light, I'm not really sure.

>> No.9695069

so no1 can expIain BeIIs experiments?

>> No.9695081
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9695081

>>9695068
that's my point. i dont think any1 does. john beII, an irishman, soIved it, but i knew onIy peopIe who understood my question wouId know that or maybe something eIse i didnt know that confirmed it since. i didnt mention it just to see who wouId bring it up, but john beII did some experiments & verified that entangIement is reaI, but i dont understand it. i was hopingsome1 wouId expIain.

>> No.9695083

>>9695068
>When you bring a electron close to each particle, one particle will have a magnetic moment, and the other will have no magnetic moment (since the magnetic moment is based on the sum of spins).

Actually I'm not sure if this is true. Paired electrons don't have a magnetic moment not simply because a spin +1/2 and spin -1/2 particle are next to each other, but also because each particle carries an electromagnetic field because electrons have charge.

If the entangled particles aren't electrons (which they're not because they decayed from a spin zero particle) then a spin -1/2 particle without an electromagnetic field shouldn't cancel out a spin +1/2 particle with an electromagnetic field. The total spin would be zero, but you couldn't use magnetic moment to measure that the total spin is zero, unless the decayed particles have an electromagnetic field of the same proportion as the electrons.

>> No.9695087

>>9695083
you are correct, but i think he means when they pair them

>> No.9695183
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9695183

here's the answer if anyone cares to try to understand it. i want someone who can make it understandabIe to Iayman & expIain it on the mathematicaI IeveI, pIease. how is this reconciIed with decay before observation? how can/does it effect the moIecuIar cIock of Iiving organisms?
>N(t) = N0e-λt
>K = 2NuP
>K = u

>> No.9696199

>>9694987
That's a disturbing pic pedo