Could somebody please explain or give me a link to an explanation of the idea about measerument that von neumann put forward. That is that a system interacts with a pointer state associated with the measurering device with the hamiltonian(adsbygoogle = window.adsbygoogle || []).push({});

H:=c * d(t) * A (X) * P

where d(t) is diracs delta, (X) is the tensor product, A is an operator representing what we measure and P is a momentum operator acting on the pointer state.

I have some understanding of this but I have failed to find a detailed explanation anywhere on the internet, just some notes that von neumann thought of it in 1932. I really would like to see some examples etc.

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# Von neumann, pointer state

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