Rare-earth emitters for quantum photonics

I will present recent results on two rare-earth doped platforms designed for quantum light storage and engineering. We use highly coherent erbium dopants in thin-film lithium niobate to escape the typical limits of integrated photonics and achieve storage times and frequency resolutions that are typically only possible with bulk optical components, including nearly microsecond long delays and MHz-bandwidth resonant features. We also show excellent coherence in europium emitters at extremely high densities in stoichiometric crystals, exploring new possible regimes for rare-earth based quantum memory.