Improvement of High-Capacity Three-Party Quantum Secret Sharing with Single Photons in both the Polarization and the Spatial-Mode Degrees of Freedom

Recently, Wang et al. put forward a high-capacity three-party quantum secret sharing (QSS) protocol with single photons in both the polarization and the spatial-mode degrees of freedom (Int J Theor Phys (2013) 52:1043–1051). In this paper, the communication capacity of Wang et al.’s QSS protocol is improved by providing more composite unitary operations for Alice’s encoding. Compared with Wang et al.’s QSS protocol, the improved protocol doubles the communication capacity of the photon for sharing Alice’s secret bits. The improved protocol only needs two-qubit single-photon states in both the polarization and the spatial-mode degrees of freedom and single-photon measurements. Compared with the QSS protocols based on entangled states and entangled state measurements, the improved protocol is more feasible.