Direct observation of quantum coherence in single-molecule magnets.

Direct evidence of quantum coherence in a single-molecule magnet in a frozen solution is reported with coherence times as long as T{2}=630+/-30 ns. We can strongly increase the coherence time by modifying the matrix in which the single-molecule magnets are embedded. The electron spins are coupled to the proton nuclear spins of both the molecule itself and, interestingly, also to those of the solvent. The clear observation of Rabi oscillations indicates that we can manipulate the spin coherently, an essential prerequisite for performing quantum computations.