Uncertainty Evaluation of an 171Yb Optical Lattice Clock at NMIJ

We report an uncertainty evaluation of an Yb-171 optical lattice clock with a total fractional uncertainty of 3.6x10(-16), which is mainly limited by the lattice-induced light shift and the blackbody radiation shift. Our evaluation of the lattice-induced light shift, the density shift, and the second-order Zeeman shift is based on an interleaved measurement where we measure the frequency shift using the alternating stabilization of a clock laser to the 6s(2) S-1(0)-6s6p P-3(0) clock transition with two different experimental parameters. In the present evaluation, the uncertainties of two sensitivity coefficients for the lattice-induced hyperpolarizability shift d incorporated in a widely used light shift model by RIKEN and the second-order Zeeman shift a(Z) are improved compared with the uncertainties of previous coefficients. The hyperpolarizability coefficient d is determined by investigating the trap potential depth and the light shifts at the lattice frequencies near the two-photon transitions 6s6p(3)P(0)-6s8p P-3(0), 6s8p P-3(2), and 6s5f(3)F(2). The obtained values are d = -1.1(4) mu Hz and a(Z) = -6.6(3) Hz/mT(2). These improved coefficients should reduce the total systematic uncertainties of Yb lattice clocks at other institutes.