Quantum state sharing is a protocol where perfect reconstruction of quantum
states is achieved with incomplete or partial information in a multi-partite
quantum networks. Quantum state sharing allows for secure communication in a
quantum network where partial information is lost or acquired by malicious
parties. This protocol utilizes entanglement for the secret state distribution,
and a class of "quantum disentangling" protocols for the state reconstruction.
We demonstrate a quantum state sharing protocol in which a tripartite entangled
state is used to encode and distribute a secret state to three players. Any two
of these players can collaborate to reconstruct the secret state, whilst
individual players obtain no information. We investigate a number of quantum
disentangling processes and experimentally demonstrate quantum state
reconstruction using two of these protocols. We experimentally measure a
fidelity, averaged over all reconstruction permutations, of F = 0.73. A result
achievable only by using quantum resources.Comment: Published, Phys. Rev. A 71, 033814 (2005) (7 figures, 11 pages
