Title: quantum mechanics - Observer effect, do this mean literally someone or just any interaction with other matter? - Physics Stack Exchange
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Observer effect, do this mean literally someone or just any interaction with other matter?
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Content: Maybe if you rephrase a bit I could give an answer. Share
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answered Apr 11 '13 at 2:39
Kevin Driscoll
Kevin Driscoll
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I am going to try to ask this question from the point of view of the Copenhagen interpretation of quantum mechanics (pioneered by Niels Bohr). However, regardless of the overall interpretation, the mathematical description of measurements in quantum mechanics is a well-established theory. The interpretation of the quantum state in the Copenhagen view, is that it represents the amount of information available about a physical system . What is peculiar about quantum mechanics is, that this information is limited in a specific sense. This implies, e.g., that it is impossible to assign values to what is called complementary observables (such as momentum and position as mentioned above). In the Copenhagen interpretation, it is only allowed to ask question regarding the probability for observing outcomes of a specific choices of measurement. Since the quantum state reflects the amount of information available it naturally changes when a measurement is performed, since we now know more... This is similar to Bayes theorem from regular probability theory, where a gain in information is reflected in an updated, changed, probability distribution for our unknown information. Thus, in this view, the quantum state is not so much a property of the system, but a reflection of the observers knowledge about the system. If you have heard of the Bayesian approach to classical probability theory, this is quite similar.