HIERARCHICAL AND PROBABILISTIC QUANTUM STATE SHARING WITH A NONMAXIMALLY FOUR-QUBIT CLUSTER STATE

A scheme that probabilistically realizing hierarchical quantum state sharing of an arbitrary unknown qubit state with a nonmaximally four-qubit cluster state is presented in this paper. In the scheme, the sender Alice distributes a quantum secret with a Bell-state measurement and publishes her measurement outcomes via a classical channel to three agents who are divided into two grades. One agent is in the upper grade while other two agents are in the lower grade. Then introducing an ancillary qubit, the agent of the upper grade only needs the assistance of any one of the other two agents for probabilistically getting the secret, while an agent of the lower grade needs the help of all the other two agents by implementing a controlled-NOT operation and a proper positive operator-valued measurement instead of usual projective measurement. In other words, the agents of two different grades have different authorities to reconstruct Alice's secret by a probabilistic manner. Moreover, the total success probability and the maximum success probability of the scheme are also worked out.