We investigate the potential for optical quantum technologies of Pr 3+ :Y2O3 in the form of monodisperse spherical nanoparticles. We measured optical inhomogeneous lines of 27 GHz, and optical homogeneous linewidths of 108 kHz and 315 kHz in particles of 400 nm and 150 nm average diameters respectively for the 1 D2(0)↔ 3 H4(0) transition at 1.4 K. Furthermore, ground state and 1 D2 excited state hyperfine structures in Y2O3 are here for the first time determined by spectral hole burning and modeled by complete Hamiltonian calculations. Ground-state spin transitions have energies of 5.99 MHz and 10.42 MHz for which we demonstrate spin inhomogeneous linewidths of 42 and 45 kHz respectively. Spin T2 up to 880 µs was obtained for the ±3/2 ↔ ±5/2 transition at 10.42 MHz, a value which exceeds that of bulk Pr 3+ doped crystals so far reported. These promising results confirm nanoscale Pr 3+ :Y2O3 as a very appealing candidate to integrate quantum devices. In particular, we discuss here the possibility of using this material for realizing spin photon interfaces emitting indistinguishable single photons.

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