  A simulation of decoherence as random noise in the Hamiltonian is studied.
The full Hamiltonian for the rf Squid is used, with the parameters chosen such
that there is a double-potential well configuration where the two
quasi-degenerate lowest levels are well separated from the rest. The results
for these first two levels are in quantitative agreement with expectations from
the ``spin 1/2'' picture for the behavior of a two-state system.
