Quantum Entanglement

Hello everyone! It's Cassie here with another blog about Quantum Mechanics. So as the title suggests, it shall be about the heart of Quantum Physics i.e. Quantum Entanglement. So without taking much of your time, let's begin with it!

#Conquer

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Quantum entanglement has applications in the emerging technologies of quantum computing and quantum cryptography, and has been used to realize quantum teleportation experimentally. At the same time, it prompts some of the more philosophically oriented discussions concerning quantum theory.

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So what is quantum entanglement?

The bookish definition:

“Quantum entanglement is a physical phenomenon that occurs when a group of particles are generated, interact, or share spatial proximity in a way such that the quantum state of each particle of the group cannot be described independently of the state of the others, including when the particles are separated by a large distance.”

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You’ll be like cut to the chase Cassie ! Enough of gibberish!

Let’s elevate Schrödinger’s thought experiment to the next level .

This time take two boxes and two kittens placed in those boxes with their life at stake because of human nuisance (yeah radioactive substance/ bomb placed by human)

We end up with 4 cases possible as shown

(Okay these doesn't looks like cats but these are the best I could draw :joy: let's just hope that "my so called kittens"will help you to understand the concept better )

But Quantum entanglement tells us to rule out the possibilities where both cats are dead and both cats are alive . Why? Scratch your head a lil’ bit! Do you recall the 50-50 odds . If you my last post on Schrödinger’s cat thought experiment , I told you in brief that if we repeated the same experiment a number of times ; half of the boxes kitty is dead and half of the boxes it’s alive .There’s always a 50% chance of occurrence of both the events.

Now ruling out two possibilities we end up with two cases . Either kitty is alive in box 1 then it’s dead in box 2 and if it’s alive in box 2 then it’s dead in box 1 . Do you see where we are going with kittens? The state i.e. existence of both the cats are practically depended on each other . Even if we take these boxes to two different ends of the universe . When we open one of the boxes and find that cat is alive then the cat in the other end of universe is dead . So how does two bombs conspire such that one blows up while other doesn’t ?

You are thinking “are physicist only concerned with cats?” Of course no! They are also into dogs . Okay no stupid jokes. Replace the cat+bomb scenario with two electrons of opposite spins . The meaning of spin is beyond your interpretation of one electron revolving clockwise and other going counter-clockwise but for our simplicity let’s consider your assumption of spin to be absolutely right. So taking the two electrons to opposite ends of universe and opening one box to recognize that it’s the electron with spin up, the other electron instantly know that it’s spin down.

Now this is what befuddled the genius Einstein’s mind and he called it "spooky action at a distance" because he argued that ends of universe means a huge distance say googol light years apart then how can information about existence of one particle reach the another particle? This indicates information traveling faster than speed of light?(Speed of light: literally on the basis of which Einstein’s entire career was built on !) Is relativity violated ? No this does not mean that relativity is violated. It means that the quantum world(i.e. our world) is different from our classical notions of reality.

You may have also heard about the dispute between Bohr and Einstein on quantum Entanglement, let's just save it for some other day and stick to our Einstein for now .Well Einstein did prefer an alternate explanation that all along the particles contained hidden information about which spin they would have. It’s just we didn’t know the information until we looked at it . Think of it this way that before tossing a coin I asked you what’s the probability of it coming heads? You’ll say 50% . I tossed the coin and it landed on my palm and now I’m again asking you what’s the probability it’s heads? Now Einstein said that it’s either 0% or 100% because the coin has already landed at conclusion it is just that the result is hidden from you(observers). Since the information was within those particles from the moment they were formed at the same point in space no information signal would have traveled between the two particles faster than speed of light.

But there’s a lot of drama over interpreting the results of Quantum entanglement. Some physicist believe that there’s hidden information in quantum particles and that it only makes sense to talk about spin after we measure them while other physicist believes that entangled particles can each other at a pace faster than light to update about their hidden information when one of them is measured . But both of them agreed that we can’t use quantum particles to communicate faster than light. Why? Ultimately, you can’t force an entangled particle into a particular state and you can’t force a measurement to produce a particular outcome because the results of quantum measurement are random.

Which makes us wonder what is reality?

So that's all from me today.

Untill the next time,

Cassie.

~ Thanks for visiting! ~