  The prospect of developing magnetic qubits is discussed. The first part of
the article makes suggestions on how to achieve the coherent quantum
superposition of spin states in small ferromagnetic clusters, weakly
uncompensated antiferromagnetic clusters, and magnetic molecules. The second
part of the article deals with mechanisms of decoherence expected in magnetic
systems. Main decohering effects are coming from nuclear spins and magnetic
fields. They can be reduced by isotopic purification and superconducting
shielding. In that case the time reversal symmetry of spin Hamiltonians makes
spin-phonon coupling ineffective in destroying quantum coherence.
