Quantum state sharing of an arbitrary two-qubit state with two-photon entanglements and Bell-state measurements

Two schemes for sharing an arbitrary two-qubit state based on entanglement swapping are proposed with Bell-state measurements and local unitary operations. One is based on the quantum channel with four Einstein-Podolsky-Rosen (EPR) pairs shared in advance. The other is based on a circular topological structure, i.e., each user shares an EPR pair with his neighboring one. The advantage of the former is that the construction of the quantum channel between the agents is controlled by the sender Alice, which will improve the security of the scheme. The circular scheme reduces the quantum resource largely when the number of the agents is large. Both of those schemes have the property of high efficiency as almost all the instances can be used to split the quantum information. They are more convenient in application than the other schemes existing as they require only two-qubit entanglements and two-qubit joint measurements for sharing an arbitrary two-qubit state.