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I'll never understand entanglement. Every explanation makes me wonder why it can't be used to instantaneously send a message. I never fully understand the explanations why it can't be used to do so. I don't understand how you can be sure about the state of the other particle, what if someone already measured it and then did something to it?
I'll never understand entanglement. Every explanation makes me wonder why it can't be used to instantaneously send a message. I never fully understand the explanations why it can't be used to do so. I don't understand how you can be sure about the state of the other particle, what if someone already measured it and then did something to it?
Earlier quoted context omitted.
That's not a bad analogy, but you have to be very careful here because no classical analogy can be a perfect fit for entanglement. The wave function is deeply and fundamentally different than our classical reality, and there is no way to reproduce its behavior classically. Among the fundamental differences is the fact that classical information can be copied but quantum states cannot be cloned. This is IMHO the singl…
A classical analogy for entanglement: suppose I have two balls in a bag. They are identical in every way, except one is red and the other is blue. I randomly grab one in each hand and show my hands closed. Now the states of the ball are entangled: as soon as you see the color of one ball, that "determines" the color of the other. (Not claiming that this is a perfect analogy, but I don't see where it diverges from how…
Bell's theorem describes the highest possible upper bound of correlations for spin measurements along different axis if it was as you say. But it turns out that in practice they are more correlated than what would be possible according to Bell's theorem, ergo, that analogy (which, in general, is plausible and reasonable) is not compatible with the physical reality we live in.
I'll never understand entanglement. Every explanation makes me wonder why it can't be used to instantaneously send a message. I never fully understand the explanations why it can't be used to do so. I don't understand how you can be sure about the state of the other particle, what if someone already measured it and then did something to it?
Neither of you can choose what the state of either particle is. You have no control, so there's no way to transmit information.
What you can do is agree in advance that you will both take certain actions based on the measured state of the particles. There's no way to be sure the person at the other end actually does so though.
Earlier quoted context omitted.
That's not a bad analogy, but you have to be very careful here because no classical analogy can be a perfect fit for entanglement. The wave function is deeply and fundamentally different than our classical reality, and there is no way to reproduce its behavior classically. Among the fundamental differences is the fact that classical information can be copied but quantum states cannot be cloned. This is IMHO the singl…
A classical analogy for entanglement: suppose I have two balls in a bag. They are identical in every way, except one is red and the other is blue. I randomly grab one in each hand and show my hands closed. Now the states of the ball are entangled: as soon as you see the color of one ball, that "determines" the color of the other. (Not claiming that this is a perfect analogy, but I don't see where it diverges from how…
This gets used to explain entanglement but it really has absolutely nothing to do with it. This is nothing that the ancient Greeks wouldn't have known.
Not to pick on you specifically, but do people really think it took a major revolution in physics in order to understand that if there are two balls, one is blue and one is red, then if you see one of the balls is red, you can conclude the other ball is blue?
It's something that I think humans can solve at the age of 3.
The failure in your explanation is right when you state that "one of the balls is red and the other is blue". The entire point of entanglement is that such a statement is not possible, that's a strictly classical interpretation. Rather, both balls are in a superposition of being both red and blue simultaneously, and it is not possible in principle to assign a color to either one of them until the moment a measurement is made.
Earlier quoted context omitted.
Those objections to super determinism seem weak, or more along the lines of “I don’t like the implications, so I won’t consider it.” Genuine question: Would quantum computers work in any deterministic framework?
I've quoted it before but I will again just because I hate superdeterminism so much: First, the logical flow: Bell’s theorem proves that no local, realistic theory can reproduce the predictions of quantum mechanics. It does so by considering a very specific situation of entangled particles being measured by spin detectors set at different angles. Critically, the angles of these spin detectors are assumed to be set in…
e.g Anything could be predicted with absolute knowledge of the starting state of the universe, and infinite computing power, but in most practical cases the causal connections between seemingly unrelated objects is irrelevant and as good as random?
I'll never understand entanglement. Every explanation makes me wonder why it can't be used to instantaneously send a message. I never fully understand the explanations why it can't be used to do so. I don't understand how you can be sure about the state of the other particle, what if someone already measured it and then did something to it?
Imagine you have a pouch with a red and a blue marble in it, then take out a marble without looking at it and hand the pouch to a friend. Later, if you look at your marble, you instantly have information about the other marble at a speed greater than the speed of light... but you couldn't use that fact to send a message. The only difference in quantum physics is that there are actually two parallel universes: One in…
I don't think it is helpful to talk about multiple universes, that makes a strong implication towards a many world interpretation. It is better to say that the difference is that in the classical case the decision who gets which marble happens when one of the marbles is taken out of the pouch while in the case of entanglement we do not really know when the decision happens but it does provably work differently than in the classical case. It might be that the decision is never truly made, that both outcomes happen in two parallel worlds, it might be that the decision is only made when one party inspects their marble, it might be that it happens at the same time as in the classical example, ...we don't know.
I'll never understand entanglement. Every explanation makes me wonder why it can't be used to instantaneously send a message. I never fully understand the explanations why it can't be used to do so. I don't understand how you can be sure about the state of the other particle, what if someone already measured it and then did something to it?
Indeed, you are only sure about the state of the other particle in the instant just after they measured it. Whoever measures first instantly destroys the entanglement link, so if they chose to manipulate the particle after measurement, you will have no knowledge of these manipulations.
More generally, note that in quantum mechanics "reading" the state of a particle (i.e. performing a measurement) is drastically different than "writing" information by manipulating a particle. Most entanglement-related weirdness hinges on this fundamental asymmetry between "read" and "write" operations for quantum information.
Earlier quoted context omitted.
It's not really immutable as you can change the parameters of an entangled pair. You just can't communicate any information by doing so, because you need a classical signal to make sure you don't read one of the particles the wrong way.
I could be WAY off, but if locality isn’t entirely true, and the “read success” is 33-67%, doesn’t that still leave quite a bit of wiggle room for communicating information in some fault tolerant method?
One side doing their interaction may cause a "spooky action at a distance" (according to some QM interpretations), but if you have only one side of readings and don't know what the other party measured in their interactions, you can't tell anything about what "the other side" did, so it does not help communication at all because you still need to transmit as many bits in a non-quantum way until you can do anything.