# Can one speak of the wave function of a object measured?

1. Apr 5, 2013

Elementary question:
When one talks of a wave function of a measured object collapsing or decohering or splitting (pick your interpretation), what we base everything on is the measuring pointer. So, which of the following is the case?
(a) one calculates with help of coupling constants etc. what wave function of the measured object must correspond to the definite state of the measuring object, or
(b) wave function of the measured object is just shorthand for "the wave form of the measuring device" ?
Thanks.

2. Apr 5, 2013

### psmt

In the case of a von Neumann (or Pauli?) measurement of the first kind i think a) is right.

For a measurement of the second kind, it looks like the answer is similar to a) but the state of the measured object after the measurement doesn't actually end up being the state you've measured, due to a "back action" of the detector, according to http://www.stanford.edu/~rsasaki/AP226/text4.pdf [Broken]

Last edited by a moderator: May 6, 2017
3. Apr 5, 2013