Nonlocality activation in entanglement swapping chains
  We consider multiple entanglement swappings performed on a chain of bipartite states. Each state does not violate CHSH inequality. We show that before some critical number of entanglement swappings is achieved the output state does not violate this inequality either. However, if this number is achieved then for some results of Bell measurements obtained in the protocol of entanglement swapping the output state violates CHSH inequality. Moreover, we show that for different states we have different critical numbers for which CHSH inequality is activated. 
Waldemar K{\l}obus, Wies{\l}aw Laskowski, Marcin Markiewicz, Andrzej   Grudka
quant-ph