Chun-Yan Li

Multiparty quantum state sharing of an arbitrary two-particle state with Einstein-Podolsky-Rosen pairs

A scheme for multiparty quantum state sharing of an arbitrary two-particle state is presented with Einstein-Podolsky-Rosen pairs. Any one of the N agents has the access to regenerate the original state with two local unitary operations if he collaborates with the other agents, say the controllers. Moreover, each of the controllers is required to take only a product measurement {sigma}{sub x}x{sigma}{sub x} on his two particles, which makes this scheme more convenient for the agents in the applications on a network than others. As all the quantum source can be used to carry the useful information, the intrinsic efficiency of qubits approaches the maximal value. With a new notation for the multipartite entanglement, the sender need only publish two bits of classical information for each measurement, which reduces the information exchanged largely.

Efficient symmetric multiparty quantum state sharing of an arbitrary m-qubit state

We present a scheme for symmetric multiparty quantum state sharing of an arbitrary m-qubit state with m Greenberger–Horne–Zeilinger states following some ideas from the controlled teleportation (2005 Phys. Rev. A 72 02338). The sender Alice performs m Bell-state measurements on her 2m particles and the controllers need only take some single-photon product measurements on their photons independently, not multipartite entanglement measurements, which makes this scheme more convenient than the latter. Also it does not require the parties to perform a controlled-NOT gate on the photons for reconstructing the unknown m-qubit state and it is an optimal one as its efficiency for qubits approaches 100% in principle.

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

Abstract.nTwo schemes for sharing an arbitrary two-qubit state based onnentanglement swapping are proposed with Bell-state measurementsnand local unitary operations. One is based on the quantum channelnwith four Einstein-Podolsky-Rosen (EPR) pairs shared in advance.nThe other is based on a circular topological structure, i.e., eachnuser shares an EPR pair with his neighboring one. The advantage ofnthe former is that the construction of the quantum channel betweennthe agents is controlled by the sender Alice, which will improventhe security of the scheme. The circular scheme reduces thenquantum resource largely when the number of the agents is large.nBoth of those schemes have the property of high efficiency asnalmost all the instances can be used to split the quantumninformation. They are more convenient in application than thenother schemes existing as they require only two-qubitnentanglements and two-qubit joint measurements for sharing annarbitrary two-qubit state.n

Quantum secure direct communication network with Einstein–Podolsky–Rosen pairs

Abstract We discuss the four requirements for a real point-to-point quantum secure direct communication (QSDC) first, and then present two efficient QSDC network schemes with an N ordered Einstein–Podolsky–Rosen pairs. Any one of the authorized users can communicate another one on the network securely and directly.

Multiparty quantum secret splitting and quantum state sharing

Abstract A protocol for multiparty quantum secret splitting is proposed with an ordered N Einstein–Podolsky–Rosen (EPR) pairs and Bell state measurements. It is secure and has the high intrinsic efficiency and source capacity as almost all the instances are useful and each EPR pair carries two bits of message securely. Moreover, we modify it for multiparty quantum state sharing of an arbitrary m-particle entangled state based on quantum teleportation with only Bell state measurements and local unitary operations which make this protocol more convenient in a practical application than others.

Quantum secure direct communication network with superdense coding and decoy photons

A quantum secure direct communication network scheme is proposed with quantum superdense coding and decoy photons. The servers on a passive optical network prepare and measure the quantum signal, i.e. a sequence of the d-dimensional Bell states. After confirming the security of the photons received from the receiver, the sender codes his secret message on them directly. For preventing a dishonest server from eavesdropping, some decoy photons prepared by measuring one photon in the Bell states are used to replace some original photons. One of the users on the network can communicate to any other one. This scheme has the advantage of high capacity, and it is more convenient than others as only a sequence of photons is transmitted in quantum line.