  We propose a quantum feedback scheme for producing deterministically
reproducible spin squeezing. The results of a continuous nondemolition atom
number measurement are fed back to control the quantum state of the sample. For
large samples and strong cavity coupling, the squeezing parameter minimum
scales inversely with atom number, approaching the Heisenberg limit.
Furthermore, ceasing the measurement and feedback when this minimum has been
reached will leave the sample in the maximally squeezed spin state.
