  Entangled spin states are created by implanting muons into single crystal
LiY0.95Ho0.05F4 to form a cluster of correlated, dipole-coupled local magnetic
moments. The resulting states have well-defined energy levels allowing
experimental manipulation of the state populations by electromagnetic
excitation. Experimental control of the evolution of the muon spin polarization
is demonstrated through application of continuous, radio-frequency magnetic
excitation fields. A semiclassical model of quantum, dipole-coupled spins
interacting with a classical, oscillating magnetic field accounts for the muon
spin evolution. On application of the excitation field, this model shows how
changes in the state populations lead to the experimentally observed effects,
thus enabling a spectroscopic probe of entangled spin states with muons.
