When you observe it, you collapse the wave-function of which color the ball has into a particular value (red or blue). Before you observed it, the ball was in a superposition of the two colors. And this collapse instantaneously also collapses the wave-function to the American ball.
Now, that is obviously not true for macroscopic objects like balls. Those are not in a superposition of colors until they are observed, but it is true for quantum objects like electrons.
> Now, that is obviously not true for macroscopic objects like balls. Those are not in a superposition of colors until they are observed, but it is true for quantum objects like electrons.
But then what is it that can I do with two entangled electrons that I can't do with two literal billiard balls known to be different colors than one another?
You can prepare a pair of photons in a state such that when you measure the polarization of both of them along the same axis, for whatever direction you want to choose, you get the same result. But they are entangled, each photon considered separately is not in a well-defined state.
You can also prepare two photons in the same state, so the have the same polarization for some direction chosen at that time. But the measurements along other axis won't be perfectly correlated (if they are correlated at all).
The red/blue color example is too simple to be interesting.
The ball example is insufficient and misleading. It is unfortunately too simple as you need 3 inputs and 2 output to demonstrate the effect (aka Mermin device).
The way to think about it is a box with 3 buttons. There is no such thing as 'observation', the only way you can interact is to push one of the 3 buttons and as a result the box will output either a red or green light.
You must push a button to get the light, but the button may mutate the internal state of the box. Using this model, there's nothing special about human or conscious observation. Every interaction via a particle or otherwise is simply pushing a button.
The crazy thing is.. no matter how clever an algorithm you write to drive the lights from the buttons, you cannot match the observed probabilities. (100% if the same button is pushed, 25% if different buttons are pushed).
> Using this model, there's nothing special about human or conscious observation. Every interaction via a particle or otherwise is simply pushing a button.
But there is something kind-of-special about the box with the buttons and the lights.
Not every interaction is simply pushing a button that lights one lamp or another. Keeping the analogy, the result of an interaction between two particles may be a combination of the "red on", "green on" states. You need to keep adding particles to have a box with buttons and lamps that works as expected.
Parallel realities. In one red goes to the US in another blue. In another vice versa. They decohere to one with someone who's seen red one who's seen blue.
Maybe this is a basic question - but what I don’t understand is why this is called “spooky” action.
My intuition is you have two particles, and you don’t know what concrete states they are in, but you know all possible states (that may be represented as some sort of system of equations).
By observing a single particle you unlock a variable in that system of equations and can therefore solve the whole thing. To me it would be more straightforward to say the concrete state of the particle is simply unknown until it is observed. The concept of superposition seems like an overly complex description for this phenomenon.
I understand my view is wrong, but I don’t understand how I’m wrong
In other words, modeling particle pairs as having matching static hidden "meta data" in them doesn't work. They do act as if there is instantaneous communication between the particles, but in a limited way that prevents us from using them for instant communication. Quantum mechanics is a weird tease, having magical properties that always serve up loopholes when we try to leverage the magic for real-world benefits. The quantum universe seems built by insurance lawyers who are masters at screwing consumers with fine-print when they go to make a claim.
I observe my particle here, and in doing so its state is decided.
The state of the entangled particle over there, a light year away (for example) is also decided. Instantly. Faster than the speed of light. Nothing travelled from here to there. No particle, no photon, nothing. How does over there "know" that I did something over here?
Sure feels kind of spooky.
To me it would be more straightforward to say the concrete state of the particle is simply unknown until it is observed.
It's not just unknown. It's undecided. It has no concrete state. It's not that it IS a one or a zero and you just don't know it. It's not yet been decided whether it's a one or a zero, but as soon as the decision is made for one of the entangled particles, the decision is also made for the other one, a light year away. Instantly. Spooky.
What you are describing is a hidden variable theory - i.e. there is some concrete state of the particles, but it is hidden.
John Bell demonstrated that in order for a hidden variable theory to make predictions in agreement with quantum mechanics, it must have nonlocal interactions, which means any workable hidden variable theory must also be pretty spooky.
Obligatory "not a quantum physicist," but the only way to observe something is to throw something at it (e.g. a photon) and see what bounces back. The problem is that when you throw something at it, you're interacting with and affecting the ball.
Do (non)measurements taken this way 'collapse the wave function' anyway? Or can you only get information that is still open to change during the actual measurement?
