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Can the Quantum Zeno Effect be solely attributed to decoherence?

  1. Nov 2, 2009 #1
    Can the Quantum Zeno Effect be solely attributed to decoherence? In every single case?

    Is the concensus on this matter opinion, or rigorously tested fact in which every case can be attributed to decoherence?

    On a more well known note, can the supposed wavefunction collapse (which gives rise to the quantum zeno effect) be entirely attributed to decoherence?

    Can a wavefunction collapse without any decoherence? (Or maybe there's always some sort of decoherence if the particle exists in the universe?)

    Also, doesn't decoherence kind of disprove the many worlds interpretation (obviously it hasn't, or this interpretation wouldn't exist anymore..)? Are we supposed to believe that we have somehow ended up in this universe out of infinite potentials where decoherence exists and continues to exist?
  2. jcsd
  3. Nov 2, 2009 #2
    Decoherence is not a physical phonemenon. It's just a descriptive word.

    Quantum Zeno Effect only works in a narrow set of systems.
  4. Nov 2, 2009 #3
    I thought decoherence was something along the lines of a wavefunction collapsing due to its interaction with the surrounding environment?
    An attempt to solve/better understand the measurement problem?

    I'm probably missing the point, but if you were able to completely take decoherence out of the picture whilst measuring (I guess some of you will claim this is impossible), would the wavefunction still collapse at the time of measurement? If taking decoherence out of the picture when measuring is impossible, then why does the wavefunction not collapse prior to measurement? It is still entwined with everything, right? Shouldn't this endear a collapse? Why is it only when we introduce a measurement instrument?
    Last edited: Nov 2, 2009
  5. Nov 2, 2009 #4
    Decoherence is nothing to do with collapse. It is a physical phenomenon (hamster143!) involving 'loss of coherence', i.e. diminuition of interference terms between different branches of the wave function (the branches cease overlapping in the course of time). In the context of measurement theory, it is implied that this happens due to the establishment of correlations between the quantum system and its environment. It is nothing fancy - just ordinary Schroedinger evolution of the wave function.

    Note that all the branches continue to exist. It requires some appropriate interpretation of the wave function or an addition of 'hidden variables' to say why one branch is what one sees.

    The concept was first invented by Bohm in 1952 for his own version of the quantum theory; it was widely adopted by many others in the 1980s and subsequently.

    The quantum Zeno effect - or the watched pot never boils effect - is an excellent example of the false paradoxes created by the orthodox interpretation. Nowadays its significance is as an impressive illustration of the participatory nature of quantum measurements. As Bohm himself wrote:

    If one supposes that an electron is continually 'watched' by a piece of apparatus, the probability of transition has been shown to be zero. It seems that the electron can undergo transition only if it is not 'watched'. This appears to be paradoxical in the usual interpretation which can only discuss the results of 'watching' and has no room for any notion of the electron existing while it is not being 'watched'. But in [the de Broglie-Bohm interpretation] with its objective ontology, this puzzle does not arise because the system is evolving whether it is watched or not. Indeed, as the theory of measurement that we have outlined shows, the 'watched' system is profoundly affected by its interaction with the measuring apparatus and, so we can understand why, if it is 'watched' too closely, it will be unable to evolve at all.
    Last edited: Nov 2, 2009
  6. Nov 2, 2009 #5
    So nobody actually knows what causes the quantum zeno effect in some cases? Is it conclusive that it is the measurement apparatus interfering with the electron?
  7. Nov 3, 2009 #6
    All I'm saying is that your view of the quantum-Zeno effect depends on your preferred interpretation of quantum mechanics. If you take the orthodox position (that QM is a statistical theory of observation) then the QZE can be considered to be a paradox; on the other hand if you believe QM to be a dynamical theory of waves and particle trajectories (as Bohm does, and for what it's worth, I do) then there is nothing paradoxical about it.
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