3 ms·

What is necessary is to find in the big wave function a subsystem consisting of, say, a particle with a spin and something approximating a classical measurement

• lmm 4y ago
  For a sufficiently simplified model of a measuring device you can do that. I mean there's no getting away from having to use the Born rule, and I'm not as sanguine as Aaronson about the idea that that's adequately justified, but it's not like there's a better alternative.
  • _0w8t 4y ago
    So far nobody was able to get such model unless I missed something. And the whole point of the decoherence exercise is to avoid Born rule as it implies a truly classical subsystem and we are back to where we started.
    • lmm 4y ago
      > So far nobody was able to get such model unless I missed something. If you model it as e.g. a quantum system with a state space that describes what you're measuring, coupled to a thermal bath, then it works. What kind of model are you looking for? Real measuring instruments are probably too big to ever model the full quantum state space of all the particles they're made up of, for example. > And the whole point of the decoherence exercise is to avoid Born rule as it implies a truly classical subsystem What do you mean by "truly classical"? The Born rule implies that our experience is the same as if we found ourselves within one of an ensemble of possible classical-like states with a certain probability, but, well, experimentally that's what we do; any interpretation of quantum mechanics needs to be able to recover that reality.