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I Does the probability collapse theory of QM imply backward in time

  1. Mar 11, 2016 #1
    In the thought experiment known as Schrodinger's cat a cat is placed in a sealed box, and its life or death is tied to an uncertain quantum event such as radioactive decay. If the radioactive particle decays, the cat dies. If not, nothing happens.

    According to probability collapse QM, as I understand it, the cat is in an uncertain state until we open the box and collapse the probability wave created by the quantum event. But what if we wait ten days to open the box? Will we discover that, if the cat died, its body has decomposed for up to ten days?

    But when did the ten days of decomposition occur (or become certain)? Does probability collapse theory claim that the death of the cat does not occur (or become certain) until we open the box and the decay too is uncertain even though the biological process will appear to have taken up to ten days?

    Or does the probability collapse theory of QM imply a backward in time causation?
     
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  3. Mar 11, 2016 #2

    mfb

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    Sure.
    They occured during the ten days - in parallel to the cat living there for 10 days. They became certain when you opened the box.

    Anyway, living systems are too complex for such a superposition to happen. With some atoms, that scenario is possible.
    No.
     
  4. Mar 11, 2016 #3
    In 'Quantum Enigma' by Bruce Rosenblum and Fred Kuttner, they describe a measurement occurring. Using your example, ten days after setting up the experiment, upon measurement the appropriate history of the quantum systems is created. In principle, macroscopic objects (despite experiencing decoherence, which does -not- cause a definite reality to arise [only -apparent- collapse) are quantum systems also.
     
  5. Mar 12, 2016 #4
    Depending on the interpretation. In time symmetric interpretation the answer is yes. The beta decay interact with a decomposed cat and that decomposed cat transforms continuously backward in time into a present alive cat. Of course in not being too precise but this is the general idea within this interpretation. The"no"answer is also possible and it is related to the more traditional collapse interpretation. I tend to like more the time symmetric interpretation because it preserves locality and determinism (but loses causality -as the cat"first decomposes and then goes back to life backward in time", you know what I mean-). Anyway is just a matter of taste.
     
  6. Mar 12, 2016 #5
    Sorry I wrote something wrong. What I tried to s say, generally speaking, is that we open the box and we interact with a decomposed dead cat which transforms continuously backward in time in a dead not decomposed cat which interacts with beta decay and transforms backward in time in a present alive carry. Sorry!!
     
  7. Mar 12, 2016 #6

    Demystifier

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    No, we are in an uncertain state. The cat is in a certain state.
     
  8. Mar 12, 2016 #7
    :
    Well, my understanding (like the pulp and StevieTNZ) is that the point of the Schrodinger's Cat experiment was to tie a micro event (such as the death of a cat) to a quantum event, and so the complexity of the biological event is irrelevant. Thus, the probability theory of QM does imply backward in time causation, or perhaps more accurately, that time is suspended in the quantum system until we measure the system. Have I got that right?
     
  9. Mar 12, 2016 #8

    David Lewis

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    The backward-in-time interpretation for Schroedinger's Cat Paradox was detailed in a book by John Gribbin (Schroedinger's Kittens).
     
  10. Mar 12, 2016 #9

    mfb

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    It is still relevant. You get decoherence.
    The time-symmetric interpretation is one of many. You do not need backwards causation and most interpretations do not have that.
     
  11. Mar 13, 2016 #10
    Perhaps it's better to think of the quantum system as of an essentially spatiotemporal (existing in its space-time) object ?
    It can be considered as a superposition of histories - until it (or our uncertainty?) is reduced by observation to one "actual" decoherent history.

    Our problem seems to be the habit of imposing temporal evolution on Nature too much...
     
    Last edited: Mar 13, 2016
  12. Mar 13, 2016 #11

    Demystifier

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    That is right only in the interpretation of QM that stipulates that everything (not only time) is suspended until we measure the system.
     
  13. Mar 13, 2016 #12
    Which interpretation is this? Doesn't evolution within the isolated system continue until you open the box?
     
  14. Mar 14, 2016 #13

    Demystifier

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