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I also went through a phase where quantum entanglement seemed mundane and easily explained. However, I realized that this was merely because I was taking the an

I also went through a phase where quantum entanglement seemed mundane and easily explained. However, I realized that this was merely because I was taking the analogies too literally. The key difference between a bag of coins and a microscopic quantum system is that the contents of the bag before being observed is unknown, whereas the quantum state is actually indeterminate. By observing one entangled particle, you force the other to also take on a definite state. Read up on Bell's inequality for the experimental justification of this idea.

crontumCombudor 11y ago
By observing one entangled particle, you force the other to also take on a definite state. ...on paper.
- noobermin 11y ago
  In the lab http://arxiv.org/abs/1511.03189 http://arxiv.org/abs/1511.03189
  - reduxotron 11y ago
    We therefore reject the hypothesis that local realism governs our experiment. They reject a hypothesis. Nothing more. They did not prove that they changed an existing state. They merely decided that the state was not present, until measured. They decided a thing was not visible until looked at, because that makes more sense on paper.
    - gibybo 11y ago
      Check out https://www.youtube.com/watch?v=ZuvK-od647c https://www.youtube.com/watch?v=ZuvK-od647c It's my favorite video for explaining how we know that the state is not determined until it has been measured. It's not just a decision we thought up on paper. It is real and well proven.
      - criddell 11y ago
        If you measure the spin, wait for a bit, then measure again, is the state known between the two measurements?
        noobermin 11y ago
        Depends on the experiment. If it is a "perfect experiment" (gedankenexperiment), and you measure the spin in the same direction a second time while not perturbing the experiment in anyway, the state should be in the state you measured it before. It is now an eigenstate of the spin operator (say, if you measured in a direction z, it is an eigenstate of S_z) and it will stay that way until it is disturbed.

crontumCombudor 11y ago

By observing one entangled particle, you force the other to also take on a definite state. ...on paper.

noobermin 11y ago
In the lab http://arxiv.org/abs/1511.03189 http://arxiv.org/abs/1511.03189
- reduxotron 11y ago
  We therefore reject the hypothesis that local realism governs our experiment. They reject a hypothesis. Nothing more. They did not prove that they changed an existing state. They merely decided that the state was not present, until measured. They decided a thing was not visible until looked at, because that makes more sense on paper.
  - gibybo 11y ago
    Check out https://www.youtube.com/watch?v=ZuvK-od647c https://www.youtube.com/watch?v=ZuvK-od647c It's my favorite video for explaining how we know that the state is not determined until it has been measured. It's not just a decision we thought up on paper. It is real and well proven.
    - criddell 11y ago
      If you measure the spin, wait for a bit, then measure again, is the state known between the two measurements?
      - noobermin 11y ago
        Depends on the experiment. If it is a "perfect experiment" (gedankenexperiment), and you measure the spin in the same direction a second time while not perturbing the experiment in anyway, the state should be in the state you measured it before. It is now an eigenstate of the spin operator (say, if you measured in a direction z, it is an eigenstate of S_z) and it will stay that way until it is disturbed.