  We propose and analyze a scheme that makes use of interactions between spins
to protect certain correlated many-body states from decoherence. The method
exploits the finite energy gap of properly designed Hamiltonians to generate a
manifold insensitive to local noise fluctuations. We apply the scheme to
achieve decoherence-resistant generation of many particle GHZ states and show
that it can improve the sensitivity in precision spectroscopy with trapped
ions. Finally we also show that cold atoms in optical lattices interacting via
short range interactions can be utilized to engineer the required long range
interactions for a robust generation of entangled states.
