4 ms·

> Why do you necessitate that viewing one envelope's content _affects_ the other, rather than merely allowing to conclude the other, because some law of the uni

by emrah 5y ago

> Why do you necessitate that viewing one envelope's content _affects_ the other, rather than merely allowing to conclude the other, because some law of the universe makes it happen to be always the other color? Right, I'm not the one necessitating it. That's how quantum mechanics works for entangled particles. You can read more on this if you look up "EPR paradox".

zelphirkalt 5y ago
I read most of https://en.wikipedia.org/wiki/EPR_paradox https://en.wikipedia.org/wiki/EPR_paradox. To me it is still unclear, how all this proves, that it must be one particle or some observation of its attributes affecting the entangled other particle or observation of one of those attributes of it. The wiki article always says things like "X has shown in experiment Y, that Z.", but the details are what matters, if I am to really understand it. I guess without investing years for the mathematical background and physics background, it is hopeless, to try and understand it in an afternoon. My mind will always ask the next "but why?" question and I will be left with the feeling of not understanding it properly. Perhaps my idea how it might happen is too much of a metaphysical one? Here is what I think: I imagine entangled particles to be something like 2 sides of the same coin. Something we can observe in the known "world" (all the things we know about or can look at in a lab or experiments), but which has an actual character, somewhere/when, that we cannot grasp yet. Perhaps like an object in front of 2 light sources, throwing 2 shadows, and we observe the shadows, instead of the real object. But the shadows for us are all we currently can observe at our level of scientific understanding or with our technology. It is unclear to me, which definition of locality that object would be in or not in, reading that wiki page, so I am trying to not use that word. The problem is, how one could prove or disprove such a thing, because it is basically an "escape hatch", with which one can always say, that there is something, we do not yet see. From an "unknown object, whose shadow we can perceive" one also cannot draw many predictions, I think, so it might not be immediately useful to assume such. My guess is, that physicists stick to theories one can prove or disprove things about. Perhaps I will ask a knowledgeable coworker to explain to me, why my idea cannot be how it really is. Thanks for the pointers, I can also mention those in my questions.
- ahelwer 5y ago
  There is absolutely no way to understand quantum mechanics without learning the math. All metaphors are faulty and will lead you to incorrect conclusions. Fortunately the advent of quantum computing has made the math quite easy - it's just linear algebra of the type one would pick up within the first week of an undergraduate course. I made a video aimed at computer scientists which you might find useful: https://www.youtube.com/watch?v=F_Riqjdh2oM https://www.youtube.com/watch?v=F_Riqjdh2oM
  - qbutt 5y ago
    This talk is excellent. Thank you for that. I think an issue with communicating the lack of information transmission is that the statement usually fails to acknowledge two aspects: 1) We are unable to reliably force any one entangled particle to a specified state prior to measurement. ( You mention this more passively in a gp >"First of all, we don't know which color is in which envelope at the start." ) 2) After measuring we have now entangled our particle to our measurement. So, if after our measurement we change the state of our particle the previously entangled particle fails to reliably correlate. Information is transmitted; it's useful information that we are unable to communicate. If I give you instructions saying if the envelope contains this then do this or if it contains that then do that, you can use the information from the particle's entanglement to make that decision, but because of 2) you can only use it to make that decision reliably once, and because of 1) those two outcomes will have to be equally desirable for this form of communication; making it useless. Just roll a dice.
    - zelphirkalt 5y ago
      Couldn't one argue, that in some situations coordination via previously agreed upon criteria is worth more than which one of two decisions is made? If A and B agree upon, that B will know what A is doing in either case of discovery, then B needs only to look at their observation and will know what A's observation is (the opposite). Then B can know how A will act, because A decides what to do based on what they observe. Then B can act in a coordinated way. Even though it is only a roll of a die, it can still be helpful. For Sci-Fi example: Some alien spaceship fleet (bare with me!) wants to attack another civilization from 2 sides across wast distances. They split up waaay before that and each keeps an entangled particle. They agree upon which observation means what detail in the first fleet's attack plan. Depending on that, the second fleet will act differently on the other side. But the first fleet only decide which of the 2 strategies to use, when they are already split up, based on the observation of the entangled particle. The second fleet has to act accordingly, or the strategy will fail. Is this impossible? Or is this simply not seen as useful information in some specific definition?

by emrah 5y ago

zelphirkalt 5y ago

I read most of https://en.wikipedia.org/wiki/EPR_paradox https://en.wikipedia.org/wiki/EPR_paradox. To me it is still unclear, how all this proves, that it must be one particle or some observation of its attributes affecting the entangled other particle or observation of one of those attributes of it. The wiki article always says things like "X has shown in experiment Y, that Z.", but the details are what matters, if I am to really understand it. I guess without investing years for the mathematical background and physics background, it is hopeless, to try and understand it in an afternoon. My mind will always ask the next "but why?" question and I will be left with the feeling of not understanding it properly. Perhaps my idea how it might happen is too much of a metaphysical one? Here is what I think: I imagine entangled particles to be something like 2 sides of the same coin. Something we can observe in the known "world" (all the things we know about or can look at in a lab or experiments), but which has an actual character, somewhere/when, that we cannot grasp yet. Perhaps like an object in front of 2 light sources, throwing 2 shadows, and we observe the shadows, instead of the real object. But the shadows for us are all we currently can observe at our level of scientific understanding or with our technology. It is unclear to me, which definition of locality that object would be in or not in, reading that wiki page, so I am trying to not use that word. The problem is, how one could prove or disprove such a thing, because it is basically an "escape hatch", with which one can always say, that there is something, we do not yet see. From an "unknown object, whose shadow we can perceive" one also cannot draw many predictions, I think, so it might not be immediately useful to assume such. My guess is, that physicists stick to theories one can prove or disprove things about. Perhaps I will ask a knowledgeable coworker to explain to me, why my idea cannot be how it really is. Thanks for the pointers, I can also mention those in my questions.

ahelwer 5y ago
There is absolutely no way to understand quantum mechanics without learning the math. All metaphors are faulty and will lead you to incorrect conclusions. Fortunately the advent of quantum computing has made the math quite easy - it's just linear algebra of the type one would pick up within the first week of an undergraduate course. I made a video aimed at computer scientists which you might find useful: https://www.youtube.com/watch?v=F_Riqjdh2oM https://www.youtube.com/watch?v=F_Riqjdh2oM
- qbutt 5y ago
  This talk is excellent. Thank you for that. I think an issue with communicating the lack of information transmission is that the statement usually fails to acknowledge two aspects: 1) We are unable to reliably force any one entangled particle to a specified state prior to measurement. ( You mention this more passively in a gp >"First of all, we don't know which color is in which envelope at the start." ) 2) After measuring we have now entangled our particle to our measurement. So, if after our measurement we change the state of our particle the previously entangled particle fails to reliably correlate. Information is transmitted; it's useful information that we are unable to communicate. If I give you instructions saying if the envelope contains this then do this or if it contains that then do that, you can use the information from the particle's entanglement to make that decision, but because of 2) you can only use it to make that decision reliably once, and because of 1) those two outcomes will have to be equally desirable for this form of communication; making it useless. Just roll a dice.
  - zelphirkalt 5y ago
    Couldn't one argue, that in some situations coordination via previously agreed upon criteria is worth more than which one of two decisions is made? If A and B agree upon, that B will know what A is doing in either case of discovery, then B needs only to look at their observation and will know what A's observation is (the opposite). Then B can know how A will act, because A decides what to do based on what they observe. Then B can act in a coordinated way. Even though it is only a roll of a die, it can still be helpful. For Sci-Fi example: Some alien spaceship fleet (bare with me!) wants to attack another civilization from 2 sides across wast distances. They split up waaay before that and each keeps an entangled particle. They agree upon which observation means what detail in the first fleet's attack plan. Depending on that, the second fleet will act differently on the other side. But the first fleet only decide which of the 2 strategies to use, when they are already split up, based on the observation of the entangled particle. The second fleet has to act accordingly, or the strategy will fail. Is this impossible? Or is this simply not seen as useful information in some specific definition?