Toward bulk crystal coherence times in Eu 3+ :Y 2 O 3 nanocrystals

We present the coherent properties of the 7 F 0 ↔ 5 D 0 transition of Eu 3+ dopants in Y 2 O 3 nanoparticles, including homogeneous linewidths less than 50 kHz. Such narrow transitions create opportunities for hybrid quantum systems on the nanoscale.