Secure quantum dense coding via tripartite entangled GHZ state in cavity   QED
  We investigate economic protocol to securely encoding classical information among three users via entangled GHZ states. We implement the scheme in cavity QED with atomic qubits where the atoms interact simultaneously with a highly detuned cavity mode with the assistance of a classical field. The scheme is insensitive to the cavity decay and the thermal field, thus based on cavity QED techniques presently it might be realizable. 
Zheng-Yuan Xue, You-Min Yi, and Zhuo-Liang Cao