Magnetic dipolar ordering and quantum phase transition in Fe8 molecular magnet

We show that a crystal of mesoscopic Fe8 single molecule magnets is an experimental realization of the Quantum Ising Phase Transition (QIPT) model in a transverse field, with dipolar interactions. Quantum annealing has enabled us to explore the QIPT at thermodynamical equilibrium. The phase diagram and critical exponents we obtain are compared to expectations for the mean-field QIPT Universality class.