Revocation and reconstruction of shared quantum states

The problem of revocation of quantum states after sharing is interesting, and we ask: Is it possible for a dealer to revoke the state once shared, before the reconstruction process? Additional resources like bell states are used to help the dealer to get back the state [1]. In a three-party scenario, we show an independent way to revoke, if, for any reason, the dealer is not sure about the intention of the/any reconstructor. In general, the classical outcomes of the dealer in sharing phase are needed, to be able to reconstruct the state perfectly. When both the shareholders are dishonest^a, and without the dealer’s knowledge, collude to reconstruct, they always have some chance of succeeding. This is addressed by giving more control to the dealer by making him/her to have a quantum share as well. We give a sharing and revocation protocol with a four-qubit entangled resource shared among three parties (two qubits with the dealer and one each with the shareholders). We further consider a class of four-qubit pure entangled states as resource and explicitly find the range of parameters for which the protocol will be successful.