Coherence times and Rabi oscillations in CaWO4:Cr5+ crystal

The measured Rabi oscillations of an ensemble of spins (here the spins 3/2 of the V15 single molecular magnet) are strongly damped by the excitation ac-field. The corresponding decoherence mechanism is attributed to an electromagnetic noise created by the dipolar spin-bath, inhomogeneously driven by the microwave field. Decoherence by electronic and nuclear spin-baths express themselves very differently vs microwave power. This decoherence mechanism should apply to all types of weakly interacting ensembles of qubits, beyond magnetism.