  Quantum spin ice is an appealing proposal of a quantum spin liquid - systems
where the magnetic moments of the constituent electron spins evade classical
long-range order to form an exotic state that is quantum entangled and coherent
over macroscopic length scales. Such phases are at the edge of our current
knowledge in condensed matter as they go beyond the established paradigm of
symmetry-breaking order and associated excitations. Neutron scattering
experiments on the pyrochlore material Pr$_2$Hf$_2$O$_7$ reveal signatures of a
quantum spin ice state that were predicted by theory.
