  We study the Quantum Measurement Process in a Stern-Gerlach setup with the
spin of a silver atom as the quantum system and the position as the apparatus.
The system and the apparatus are treated quantum-mechanically using unitary
evolution. The new ingredient in our analysis is the idea that the probes
determining the position of the silver atom are limited in resolution. We show
using a Wigner matrix that due to the coarseness of the detection process, the
pure density matrix appears to evolve to an impure one. We quantify the
information gained about the spin in a coarse position measurement.
