My husband is watching YouTube and there’s a man discussing quantum entanglement.
His description: There are two particles. They can be either green or red, but they are both colors until they’re measured. Once you measure one, though, it automatically determines that the other is the same. No matter how many times you measured, or how far you separated the particles, the two would always be the same color.
Why does one being one color guarantee that the other one would be? How do they “know” to always be that color? And what sort of implication does that have for science/real world, other than being really cool?
In: Physics
Don’t sweat it, even Einstein called it “spooky action at a distance.”
Quantum can be highly unintuitive and surprising, especially as we don’t experience it in day to day lives
Imagine you have 2 cards, an Ace and a King, you shuffle them and shove each inside an envelope so you don’t know which envelope contains which card. Then you give your husband one Envelope and you keep the other.
The two envelopes are now quantum entangled, the card inside is neither the Ace nor the King, but rather a superposition of the two. If you open the envelope and see that the card you have is an Ace, you will now that your husband must have a King, no matter how close or far away you are.
This same procedure can be done for quantum system, creating 2 particles where knowing a property of one, forces you to know a property of another. The usual case is Spin, you can create a pair of particles in which one has a spin of 1/2 and the other of -1/2. You won’t knoe which is which umtil you measure it. But if you measure only one, you instantly know the spin of the other no matter how far in the universe they are.
So imagine that you order a pair of shoes, but you ship one shoe to you and another to a friend. Until you open the shoe box you could have either the left or right shoe, but the moment you open it you know you have the right shoe and your friend has the left one.
It doesn’t allow faster than light communication or anything truly weird to happen,
The “why” is.., well, if boils down to “because”. It’s simply the way the universe works.
Maybe it will help to think of entangled as.. hmm … meshing gears. If you spin one gear up in a clockwise spin, the other *has* to spin anti-clockwise.
Spin the gears up in a dark room, then put one in a box and take it to Amsterdam.
When you get that, open the box and see which way the gear is spinning.
You’ll know instantly which direction the OTHER gear is spinning.
As for implications in the macro world ( where we live)… there’s lots of arguments and downright fights about that. Myself, I lean to the “it’s seriously cool, but it won’t make my coffee in the morning” crowd
It’s basically a phenomenon where two particles are “entangled” with each other, meaning they have the same state, always. This is not only a cool phenomenon but an incredibly useful one if it could be harnessed.
The most obvious use case would be faster than light communication. Electromagnetic radiation travels at the speed of light so any long distance communication is subject to some delay. But if we were able to intentionally entangle particles and control their state, we could create faster than light communication. If one state, for example green, corresponds to 0, and red corresponds to 1, we could make entangled computers which communicate instantaneously with each other. For example spacecraft on Mars have a significant signal delay of about 15 minutes one way on average. But with two such entangled terminals you could enable instant communication, without violating any laws of physics. So rovers could be controlled in real time, which would make rover missions much more versatile and cheaper. If crews were sent to Mars, or anywhere else in space, they’d have instantaneous communication with Earth. Hell even if we sent spacecraft to another solar system, we’d still be able to have real time communication.
A key property of quantum mechanics is superposition. For example, a particle that we know can only be spinning clockwise or counterclockwise can simultaneously be doing both because of superposition. When we measure it, it will land in one of the two options – CW or CCW – randomly. This isn’t because it was secretly in one the whole time, before we measured it the particle was literally doing both.
What if that particle, however, were two particles? And maybe all we know is that they are spinning opposite of each other. And so the state is no longer CW or CCW but (CW & CCW) OR (CCW & CW). In this way both of the particles are in superposition, not just with another “version” of themselves, but in superposition with each other. If I just measure the first particle and find it to be CCW then because the only way to measure this was if it was (CCW & CW) then I know that the second particle must be CW. Because they are in superposition with each other, by measuring one of them I have forced them both to collapse their states. If the options had been (CW & CCW) OR (CCW & CCW), then measuring the first to be CW would have done nothing and so they wouldn’t be entangled. But that’s all entanglement is: The property of superposition applied to more than one particle.
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