Measurement of linewidths and permanent electric dipole moment change of the Ce 4f-5d transition in Y2SiO5 for qubit readout scheme in rare-earth ion based quantum computing

In this work the inhomogeneous (zero-phonon line) and homogeneous linewidths and the permanent electric dipole moment change (averaged value of all dipole orientations) for the Ce 4f-5d transition in Y2SiO5 were measured in order to investigate the possibility for using Ce as a sensor to detect the hyperfine state of a spatially close-lying Pr or Eu ion. The experiments were carried out on Ce doped or Ce-Pr co-doped single Y2SiO5 crystals. The homogeneous linewidth is essentially limited by the excited state lifetime. Based on the linewidth measurements, the oscillator strength, absorption cross section, and saturation intensity were calculated to be about 6.2(+/- 1.7) x 10(-7), 4.5(+/- 1.3) x 10(-19) m(2), and 1.4(+/- 0.4) x 10(7) W/m(2), respectively. The difference in permanent dipole moment, Delta mu(Ce), between the ground and excited states of the Ce ion was measured as 9.6(+/- 5.3) x 10(-30) C m. These measurements indicate that Ce is a promising readout ion to probe a single-ion qubit state for the quantum computing scheme using rare-earth ions.