Quantum secret sharing with polarization-entangled photon pairs

We describe and experimentally demonstrate a more practical three-party quantum secret sharing (QSS) protocol using polarization-entangled photon pairs. The source itself serves as an active participant and can switch between the required photon states by modulating the pump beam only, thereby making the protocol less susceptible to loss and amenable to fast switching. We derive a security proof based on quantum key distribution, demonstrating our QSS protocol to be secure against both eavesdropping and dishonest participants. Compared to three-photon protocols, the practical efficiency is dramatically improved as there is no need to generate, transmit, or detect a third photon.

Figure 1

Three-party quantum secret sharing protocol. Sara chooses one of four entangled states; Alice and Bob randomly select to measure in either the diagonal or circular bases, recording their measurement results.

Figure 2

Experimental setup. See text for details.

Figure 3

Experimentally measured outcome probabilities for Alice and Bob, conditioned on input state and measurement bases.

Figure 4

Experimentally measured correlations, as expressed by expectation of the parity of Alice's and Bob's results.