Controlled quantum secret sharing

We present a new protocol in which a secret multiqubit quantum state vertical bar Ψ) is shared by n players and m controllers, where vertical bar Ψ) is the encoding state of a quantum secret sharing scheme. The players may be considered as field agents responsible for carrying out a task, using the secret information encrypted in vertical bar Ψ), while the controllers are superiors who decide if and when the task should be carried out and who to do it. Our protocol only requires ancillary Bell states and Bell-basis measurements