61–70 of 356 posts
https://arxiv.org/abs/quant-ph/9611037
...I wonder if anyone has ever followed up on Caroline Thompson's work after she passed away.
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…
In fact, Bell’s inequality was stated as a collaboration game that can only succeed if you use entangled particles. No classical object will get you the same results.
You still can’t communicate faster than light but the reason is more subtle. The article does a good job but for a deeper explanation I’d refer to Sean Carrol: https://youtu.be/yZ1KSJbJAng
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?
edit: I didn't mean it as an explanation of entanglement. Just thought it was a convenient joke.
Earlier quoted context omitted.
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…
The only difference in quantum physics is that there are actually two parallel universes: One in which you took out the red marble & one in which you took the blue one. You don't know what universe you're in until you look at the marble, but still it doesn't help you to transmit a message to your friend. I don't think it is helpful to talk about multiple universes, that makes a strong implication towards a many world…
Earlier quoted context omitted.
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…
Is it reasonable to say the universe might be superdeterministic, but in the example of choosing measurements for an experiment(or almost any other example imaginable), it might as well be truly random as the causal links affecting the instruments isn't likely to be 'conspiring' in some way to impact the results of the experiment? e.g Anything could be predicted with absolute knowledge of the starting state of the un…
I'm not a physicist though, so I might have something wrong here.
Earlier quoted context omitted.
>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. 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 p…
> 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. I don't disagree, and (clearly) I make a measurement when I show you the color of a ball. Before I show you a ball, I would also say that the colors of the balls are in a superposition. > major revolution in physics i…
Entanglement is not a property about wave functions and really has nothing to do with waves. It's a logical consequence of the uncertainty principle and was ironically deduced by Einstein, Rosen, and Podolsky (EPR Paradox) as a way to argue that quantum mechanics is an incomplete description of physical reality. Being that it's strictly a consequence of the uncertainty principle, it applies equally well to non-wave function formulations of quantum mechanics such as the matrix formulation which does not use a wave function.
Entanglement is precisely the principle that a physical system can exist such that no part of the system can be described without describing the rest of the system as a whole. Einstein argued that this made quantum mechanics incomplete, the idea that somehow two properties of a physical system separated potentially by light years could not be decomposed into two physical systems that behaved independently of one another violated basic notions of local realism.
The issue is that as soon as you stated that one ball is red you have made a statement about some property of the physical system that is independent of the rest of the system. That is fundamentally what entanglement states you can not do. All you can state is that there are two balls that are in a superposition of being red and blue and there is no way to describe one ball as red and the other as blue, they are both red and blue simultaneously.
That is what entanglement is and that is the new principle that was neither known to the ancient Greeks or something that a 3 year old could figure out. Not the idea that if there are two balls and one ball is red and the other is blue, then if you see the red ball you know that the other ball is blue. Nothing about that ever baffled any physicist.
Earlier quoted context omitted.
Two balls are a box. Neither are spinning. The box gets “shaken up” and the balls hit each other. We know that one ball is spinning clockwise and the other is counter clockwise because angular momentum spin is conserved. The balls launch far away from each other. We know the spin is entangled in that one is clock wise the other is counter clockwise but we don’t know which is which until we measure. How do we use that…
By constraining all your communications to a game of interstellar rock paper scissors?
How is it possible to have information less than a bit, a partial bit? What is that ".5" part? Isn't a bit indivisible?
Only in the context of a character doublet is all information expressed. To know the "half bit" part, you cannot "look" at just one character, you have to look at the total. The information is shared between the two characters. Measuring the bits-per-character is only useful when considering the whole system. The "partial bits" is information smeared across the system. Changing the middle bit may change one, or both, characters.
Here's a 11 bit example, where the middle bit is changed and it changes both characters: (11101001010 vs 11101101010, or '/L' vs '%8' encoded)
https://convert.zamicol.com/?in=11101001010&inAlpha=01&outAl...
https://convert.zamicol.com/?in=11101101010&inAlpha=01&outAl...
vs changing the last bit only changes the last character: (Using the preceding example, 11101101010 vs 11101101011, or '%8' vs '%9' encoded)
https://convert.zamicol.com/?in=11101101011&inAlpha=01&outAl...
The same principle applies to information theory and cryptography. Security can be measured in "partial bits" because it's measured across something larger.
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…
Somehow they still manage to align themselves so if one person sees red the other sees blue.
Although it's even more accurate to say that if one person sees [colour] the other person sees [opposite colour].
The colours are random, but the relationship between them is fixed.
Very crudely (and rather misleadingly but never mind) this is why you can't communicate at FTL.
You need the other marble to know whether you had [colour] or [opposite colour]. And that info can't travel faster than the speed of light.
It's even more accurate to say there are no marbles anywhere - only interaction events between marble objects and people-looking-at-marble objects, and the API does not allow you to look inside either to see state.
(The state has to exist somewhere otherwise none of this would work. But Bell proves it's not inside the marbles. So it's "non-local" which is code for "we have no idea where it is".)
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…