Cooperative three- and four- player quantum games
  A cooperative multi-player quantum game played by 3 and 4 players has been studied. Quantum superposed operator is introduced in this work which solves the non-zero sum difficulty in previous treatment. The role of quantum entanglement of the initial state is discussed in details. 
Ying Jun Ma, Gui Lu Long, Fu Guo Deng, Feng Li and Sheng-Xing Zhang