Entanglement-secured single-qubit quantum secret sharing
Physical Review A 84 (2011) 32303
In single-qubit quantum secret sharing, a secret is shared between *N* parties via manipulation and measurement of one qubit at a time. Each qubit is sent to all *N* parties in sequence; the secret is encoded in the first participant’s preparation of the qubit state and the subsequent participants’ choices of state rotation or measurement basis. We present a protocol for single-qubit quantum secret sharing using polarization entanglement of photon pairs produced in type-I spontaneous parametric downconversion. We investigate the protocol’s security against eavesdropping attack under common experimental conditions: a lossy channel for photon transmission, and imperfect preparation of the initial qubit state. A protocol which exploits *entanglement* between photons, rather than simply polarization *correlation*, is more robustly secure. We implement the entanglement-based secret-sharing protocol with 87% secret-sharing fidelity, limited by the purity of the entangled state produced by our present apparatus. We demonstrate a photon-number splitting eavesdropping attack, which achieves no success against the entanglement-based protocol while showing the predicted rate of success against a correlation-based protocol.