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3 comments

Comments on this article are now closed.

• 1
  Philius Mar 8, 2013 12:52 AM Ireland

  wave functions collapse all the time

  You couldn't have nuclear fusion/fission without them.
  The fact that an atomic bomb explodes is a weak measurement, an aggregate of uncertainty, with a normal distribution.
  
  The only way a wave function can't collapse is if it exists in its own universe.

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• 2
  hchatfield Mar 26, 2013 6:49 PM Nepean, Canada

  Dead or Alive - what causes the collapse

  It occurred to me that, to answer "is the cat dead or alive" - you need information. Extraction of information from the system under consideration is what is required to answer the question and it seems to me it is the extraction of info that is the equivalent of the wave function collapse.
  
  The information you need is obtained by some sort of "measurement". You take the lid off and look. That's one way. When you lift the lid the cat is either dead or alive depending on whether of not the radiative material decayed. So we also managed to extract information about the radioactive material at the same time. But we can know nothing about what happened until we lift the lid and extract the info via observation.
  
  What about continuous extraction of info from the apparatus?
  
  How about if you hook up a bluetooth device to monitor the heart beat of the cat. You are sitting outside watching a heart beat display on your laptop. Is this an observation? Surely it is. Will the heartbeat eventually stop (cat is dead, also indicating we had a decay event in the box) - or will it keep going (cat is alive) - or will it somehow display both heartbeat / no heartbeat (i.e. both states)
  
  One might suggest that since this is a continuous observation - the "wave function" is in a state of continuous collapse. Yet - if the heart beat stops we have then extracted info about the decay event by using the cat as a measuring device. The death is a function of that event either occurring or not occurring - but does the observation of the cat's heart beat have any effect on the decay event. I have a little trouble with the logic here.

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• 3
  M. Asghar Mar 30, 2013 6:16 PM

  Underhand means with the same result

  Monitoring the heart beat of the cat by any underhand means, is the 'information': its presence shows that the cat is living and its absence means tha the cat is dead - and the entangled wavefunction has collapsed in both the cases.
  
  Quote:

  Originally posted by hchatfield View comment

  It occurred to me that, to answer "is the cat dead or alive" - you need information. Extraction of information from the system under consideration is what is required to answer the question and it seems to me it is the extraction of info that is the equivalent of the wave function collapse.
  
  The information you need is obtained by some sort of "measurement". You take the lid off and look. That's one way. When you lift the lid the cat is either dead or alive depending on whether of not the radiative material decayed. So we also managed to extract information about the radioactive material at the same time. But we can know nothing about what happened until we lift the lid and extract the info via observation.
  
  What about continuous extraction of info from the apparatus?
  
  How about if you hook up a bluetooth device to monitor the heart beat of the cat. You are sitting outside watching a heart beat display on your laptop. Is this an observation? Surely it is. Will the heartbeat eventually stop (cat is dead, also indicating we had a decay event in the box) - or will it keep going (cat is alive) - or will it somehow display both heartbeat / no heartbeat (i.e. both states)
  
  One might suggest that since this is a continuous observation - the "wave function" is in a state of continuous collapse. Yet - if the heart beat stops we have then extracted info about the decay event by using the cat as a measuring device. The death is a function of that event either occurring or not occurring - but does the observation of the cat's heart beat have any effect on the decay event. I have a little trouble with the logic here.

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