A note on superposition of two unknown states using Deutsch CTC model
  In a recent work, authors prove a yet another no-go theorem that forbids the existence of a universal probabilistic quantum protocol producing a superposition of two unknown quantum states. In this short note, we show that in the presence of closed time like curves, one can indeed create superposition of unknown quantum states and evade the no-go result. 
Sasha Sami, Indranil Chakrabarty
quant-ph gr-qc