  We present an analysis of the cooling of a micro-mechanical resonator by
means of measurements and back action. The measurements are performed via the
coupling to a Cooper-pair box, and although the coupling does not lead to net
cooling, the extraction of information and hence entropy from the system leads
to a pure quantum state. Under suitable circumstances, the states become very
close to coherent states, conditioned on the measurement record, and can hence
be displaced to the oscillator ground state.
