Multi-Receiver Quantum Dense Coding with Non-Symmetric Quantum Channel
  A two-receiver quantum dense coding scheme and an $N$-receiver quantum dense coding scheme, in the case of non-symmetric Hilbert spaces of the particles of the quantum channel, are investigated in this paper. A sender can send his messages to many receivers simultaneously. The scheme can be applied to quantum secret sharing and controlled quantum dense coding. 
Chang-Bao Fu, Shou Zhang, Ke Li, Kyu-Hwang Yeon, Chung-In Um