But what is Quantum Entanglement? (oversimplified animation) Nobel Prize in Physics 2022

Let's say Alice and Bob have this weird shaped stick and then... they break it up, they don’t look at the pieces so one would have the big piece, and other one would have a small piece. Now we send, Bob to andromeda galaxy because why not. And then he looks at his piece, it's a bigger piece and instantly he knows that Alice would have the smaller piece. There's nothing surprising about that because it was established on earth itself that one had the big piece and one had the small piece. Now qua

ntum entanglement is much weirder, it says when we break the stick, and it's simultaneously in a state where Bob have the small piece and Alice has the bigger one and Bob would have the big piece Alice has the small piece. It has not yet been determined no, it is completely in what we call a superposition but it has to match. .They have to fit together to make the original stick right but it's not actually determined who has the big piece yet and quantum mechanics allows that so Bob and Alice’ s

tick have to be entangled in such a way that they fit together correctly to make the original weird stick. Now suppose Bob takes a look and finds out that he has the big piece but what happened is somehow he seemingly forced faster than the speed of light communication from Andromeda to the earth instantaneously He forced Alice’s state to also assume a precise state. He instantaneously know that Alice has the smaller piece of stick and that's that but he doesn’t know whether Alice had looked at

it yet or not So the big question here is can you communicate from Andromeda to earth this way? No maybe not, bigger piece information was communicated nonetheless. so Alice looks at her piece and instantaneously she see the small one but she doesn’t know that it was her who collapse the wave function and so for Alice to tell Bob She would still have to send you a mail in the post or some signal that at this time I looked at my piece which obviously wont be faster than light communication. but n

either of us know who was the one who did it because it's really it's not communication faster than light it's knowledge faster than light. You can force the stick to assume a specific state faster than the speed of light and you could learn about it later like Alice can then send Bob an intergalactic mail in the post and hell get it and say oh yeah This is the quantum phenomenon called entanglement. It's what happens when any two quantum particles interact. And what results from that is that th

ose particles, once they've interacted, they are "entangled", and it means that their quantum states are interdependent. If one is in one particular state, then the other one has to have some other particular state, depending on the kind of entanglement they have. So, lets take, electrons and not sticks. And electrons have a quantum property called spin, which you don't really need to know anything about. I did another video of spin if you wanna check it out. the spin of an electron can have val

ues. An electron can be spin up or spin down. And if the electrons become entangled, ...then... this may create a situation where those two spins are correlated, such that if one of the electrons has a spin up, then the other one must have a spin down. Now, this is a prediction of Quantum Mechanics. However, here's the complication Because Niels Bohr, suggested that, in the case of quantum particles, it's not the fact that they have this property, spin or whatever, all the time. They only have t

hat property, with a fixed value, when we observe it. So, for these entangled {electrons}, if we think of sending those out to Alice and Bob, Bohr said: they DON'T HAVE a fixed orientation of their spin. All we can say is that those spins are correlated. So, if Alice then measures her electron, and finds it has spin up, then Bob's will have spin down. But that spin wasn't determined until Alice measured it. And this is where Einstein felt there was a problem because it was as if the act of Alice

measuring her electron spin... somehow affected Bob's spin. So that once Alice had found the spin had to be spin up,... somehow, magically seemed to sort of transmit some kind of influence to Bob's spin, to make sure that it was spin down. This is the most famous spooky action at a distance by Quantum Mechanics. Einstein, Podolsky and Rosen, then suggested that there has to be some alternative to this, because it is impossible for any signal, any information to be transmitted faster than light.

you can't have this instantaneous "action at a distance". And so, Einstein said that, what must be going on instead,...is that, all along, these two electrons had some property that somehow fixed their spins already. It's just that it was a property that we couldn't measure. He called them "hidden variables". How do we know if that's due to hidden variables, or just quantum mechanics? Well, then Bell came in and gave his inequality. Violating that inequality implied that there is no such thing

as hidden variables. That’s whole another topic for another video. The main point is Quantum mechanics turns out to be true.