  A new approach to the problem of measurement in quantum mechanics is
proposed. In this approach, the process of measurement is described in the
Heisenberg picture and divided into two stages. The first stage is to transduce
the measured observable to the probe observable. The second stage is to amplify
the probe observable to the macroscopic meter observable. Quantum state
reduction is derived, based on the quantum Bayes principle, from the
object-apparatus interaction in the first stage. The dynamical process of the
second stage is described as a quantum amplification with infinite gain based
on nonstandard analysis.
