Optical excitation of nuclear spin coherence in a Tm3+: YAG crystal

A thulium-doped crystal is experimentally shown to be an excellent candidate for broadband quantum storage in a solid-state medium. The nuclear spin coherence is optically excited, detected, and characterized in such a crystal. The lifetime of the spin coherence-the potential storage entity-is measured by means of a new Raman echo protocol to be about 300 μs over a wide range of ground state splittings. This flexibility, which is attractive for broadband operation and well fitted to existing quantum sources, results from the simple hyperfine structure, which contrasts to Pr- and Eu-doped crystals.