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Measurement/observation in QM

  1. Mar 3, 2009 #1
    What counts as a measurement in QM? I am having trouble with this concept and have the following questions:

    1. Can I say that by looking at a certain experiment I've collapsed the wave function into a particular state? In that case, doesn't it mean that a blind person will get a different result for a given quantum experiment?
    2. What is capable of making a measurement? Is a conscious mind required? What if, for instance, a computer takes and stores reading. In this case, does the wave function only collapses when the scientist retrieves the data from the computer?
    3. A charge object will affect the E and B field around it. Doesn't this mean that it is constantly under observation? The same can be said with any object with mass. We can always "feel" the object from its gravity, so are those measurements?
    4. After a measure, we know what state the system is in, and if we immediately take a measure of any compatible (commutable) observable, we can be sure what eigenvalue we would get. In this case, how long would the system stay in such a state? Will it be in the state forever as long as we don't that measurements of non-compatible observables?
  2. jcsd
  3. Mar 4, 2009 #2


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    question 2 object to current philosophy of science discussion. It depends also on what interpretation of QM you have, the Copenhagen or Bohm etc.

    3. there is a distinction between interaction and observation.

    1. we don't look with our eyes on the experiment, the electrons etc are too small to be seen with our eyes, therefore the need of advanced apparatus

    4. it depends on your hamiltonian which is the generator of time translations.
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