Isotropic non-locality cannot be distilled
  We investigate non-locality distillation protocols for isotropic correlations. These correlations are the hardest instances which respect to distillability and only partial results are known about their behaviour under non-locality distillation protocols. We completely resolve this issue by proving that non-locality distillation is impossible for all non-local isotropic correlations. 
Dejan D. Dukaric
quant-ph