Optics of rare-earth ions in cerium oxide for application in quantum technologies

The development of stable, long-lived solid-state quantum memory remains a significant challenge, requiring qubits with extended coherence times. Recently, rare earth ions (REIs) embedded in CeO2 crystals have emerged as promising candidates for qubit systems with extended coherence times due to several key advantages. CeO2 is considered the most isotopically purified host system. Furthermore, CeO2 is highly favorable due to its wide bandgap, which can host color centers ranging from the visible spectrum to the mid-infrared. This study focuses on Tm3+ ions embedded in CeO2. High-quality pristine and ultra-low (0.01%) Tm3+ doped CeO2 thin films were grown on single-crystal yttria-stabilized zirconia (YSZ) (100) substrates. While pristine CeO2 exhibited minimal residual photoluminescence emission, Tm3+ doped CeO2 displayed sharp emission lines in the near-infrared and visible regions. We have carried out optical characterization, including photoluminescence and photoluminescence excitation measurements, to investigate the optical coherence time of Tm atoms. Further work on these crystals may establish them as ideal candidates for quantum memories or quantum sensing applications based on ensembles of these ions.