Cold collision shift cancelation and inelastic scattering in a Yb   optical lattice clock
  Recently, p-wave cold collisions were shown to dominate the density-dependent shift of the clock transition frequency in a 171Yb optical lattice clock. Here we demonstrate that by operating such a system at the proper excitation fraction, the cold collision shift is canceled below the 5x10^{-18} fractional frequency level. We report inelastic two-body loss rates for 3P0-3P0 and 1S0-3P0 scattering. We also measure interaction shifts in an unpolarized atomic sample. Collision measurements for this spin-1/2 171Yb system are relevant for high performance optical clocks as well as strongly-interacting systems for quantum information and quantum simulation applications. 
A. D. Ludlow, N. D. Lemke, J. A. Sherman, C. W. Oates, G. Quemener, J.   von Stecher, and A. M. Rey
physics.atom-ph physics.optics