Efficient Multiparty Quantum Secret Sharing with Greenberger--Horne--Zeilinger States

An efficient multiparty quantum secret sharing scheme is proposed with Greenberger--Horne--Zeilinger (GHZ) states following some ideas in quantum dense coding. The agents take the single-photon measurements on the photons received for eavesdropping check and exploit the four local unitary operations I, σ_z, σ_x and iσ_y to code their message. This scheme has the advantage of high capacity as each GHZ state can carry two bits of information. The parties do not need to announce the measuring bases for almost all the photons, which will reduce the classical information exchanged largely. The intrinsic efficiency for qubits and the total efficiency both approach the maximal values.