3 ms·

>since it alters the state you can see that it happened afterwards in a system What experiment shows this?

• Jensson 5y ago
  https://en.wikipedia.org/wiki/Double-slit_experiment https://en.wikipedia.org/wiki/Double-slit_experiment
• simiones 5y ago
  The version of the double-slit experiment with a detector on one of the slits can be taken to show this. As you know, in the classical double-slit experiment, the screen is the only detector, and launching particles even one at a time through the slits produces the interference pattern. However, if you add a second detector in one of the slits capable of measuring if a particle passes through that slit or not, the interference pattern on the screen disappears, regardless of how many particles you send through. This is normally taken to mean that the slit detector collapses the wave function (in Copenhagen parlance); or that one particular state of the particle becomes entangled with the initial detector, which is already entangled with the screen, to there is no more constructive interference to be seen (in Many Worlds terms).
  • dekhn 5y ago
    I believe you're referring to delayed choice quantum eraser?
    • simiones 5y ago
      No, that's a different, more complex experiment. This is just about adding a detector to one of the slits so you can tell which slit each electron is passing through. Here is a more complete explanation: https://phys.org/news/2011-01-which-way-detector-mystery-double-slit.html https://phys.org/news/2011-01-which-way-detector-mystery-dou... The delayed choice quantum eraser is a much more complex experiment.