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Radioactivity and Quantum Zeno Question

  1. Jun 27, 2014 #1
    Radioactivity is independent of the time the radioactive element was produced.
    If i remember correctly (which is a big IF, correct me if I'm wrong) this has to do with the collapse of the wavefunction into a definite state by "measurements" and then slipping back into a wave to evolve again with determinism by the Schrodinger equation. Future measurements would find the particle is decayed or not with a certain probability.

    Quantum Zeno effect has been observed in that repeated "measurements" are able to slow decay of various excited states.

    So if we have a large dense lump of some radioactive isotope how does decay rate or its lifetime not depend on the amount of stuff in it. Wouldn't macroscopic section be able to "measure" (I'm using the quotes since I'm not entirely sure what constitutes as measurements) other sections repeatedly as to make that section not decay or slow it down. Density would also come into play by making the "measurements" more frequent I guess right?
  2. jcsd
  3. Jun 27, 2014 #2


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    An interesting question. I'm not sure, but the wiki article has this to say:

    By its nature, the effect appears only in systems with distinguishable quantum states, and hence is inapplicable to classical phenomena and macroscopic bodies.

  4. Jun 27, 2014 #3
    Hmmm, I wonder what it means exactly by distinguishable quantum states.

    Is this that divide between quantum systems and classical systems because there are some relatively large systems that behave quantum mechanically. And these relatively large system of radioactive isotopes would show some correlation to delayed decay if we were able to measure such small changes in decay time right?

    Sorry, Im not that far in my understanding in QM so can anyone explain when or how something becomes non distinguishable as you keep adding things to a system. The system does become more complex as you add more particles but does that make it indistinguishable or are we just unable to discern the differences.
  5. Jun 27, 2014 #4


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    For the quantum Zeno effect to work, the measurement must be sufficiently fast. More precisely, the time of measurement must be much shorter than 1/Delta H (where I use units hbar=1 and Delta H is the uncertainty of energy in the unstable state).

    In most cases Delta H is large enough (and density small enough) so that the quantum Zeno effect does not work.
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