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How/why decoherence rather than how/why coherence

  1. Jun 3, 2015 #1
    Many discussions get around the subject of how / why does decoherence happen. Interaction with the environment, getting to macroscopic scale, irreversible change of information... Somehow they seem to imply that the natural state of things in the Universe is quantum coherence and then they ask for the mechanism which collapses that into a decoherent state (wavefunction collapse).

    I wonder whether the question should not be the other way around, not so much why / how does decoherence happen but rather the opposite, why / how / what does it mean that quantum entities sometimes display coherence.

    Decoherence somehow seems to be the logical state of affairs, things having definite positions, momentums, definite histories. It is rather coherence which is puzzling, things being in a superposition of different possible realities. Should we not be looking at the issue from this point of view? Not 'things are fundamentally coherent but decoherence turns them into fixed realities' but rather 'things are normally concrete realities but under certain conditions we may make several of those coexist in a superposition for a short time'? And then ask 'how / why is it so'?
  2. jcsd
  3. Jun 3, 2015 #2


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    Science Advisor

    If one starts from the Schrodinger equation as the starting point, then coherence is something normal and decoherence something that needs to be explained. So effectively, you ask: Why Schrodinger equation in the first place?
  4. Jun 5, 2015 #3


    Staff: Mentor

    Well you are reading things into it the theory is silent about.

    But leaving that aside decoherence is nothing mysterious - its simply a kind of entanglement. Its pretty obvious with all the interactions we have in the world around us its very very difficult to stop happening.

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