Application Of Multi-particle Quantum Entangled States In Cryptographic Protocols

Comparing with traditionalclassical cryptography, the security of quantum cryptographic protocols is only guaranteed by the fundamental principles of quantum mechanics, and needs not to assume the attacker’s computing power. As an important branch of the theory of quantum cryptography, quantum cryptographic protocols have quickly developed in different application backgrounds. Furthermore, some representative protocols have also made significant progress in experiment.A private database queries protocol based on a quantum third party (TP) is proposed by utilizing the quantum correlation of three-photon GHZ state (Greenberger-Horne-Zeilinger). Our protocol is loss tolerant and robust against faked entangled states and quantum memory attack. Our proposal is deterministicand controllable with the help of the TP, and utilizes device-independent (DI) witnesses of genuine tripartite entanglement to protect the security. Our proposal is a new application environment for DI verification of entanglement.Afterwards, we propose an equivalent protocol using Bell states. It not onlyhas the advantages of the protocol using the GHZ states, but also is easy to realize.An odd particle composite quantum statecombining with W-state and Bell-state is investigated.It is shown that this composite quantum state can be used to prefect teleportation of arbitrary single and two qubits, and also can be commendably utilized to superdense coding and quantum state sharing. We present the measurement basis of sender and unity operationsof receiver for teleportation protocol. It is found thatfive classical bits can be sent by conveying three quantum bits for superdense coding.Two methods for probabilistic teleportation of the unknownthree-particle GHZ state via a partially entangled four-particle Cluster state are proposed. The first is the unitary transformation, and the second is POVM measurement (Positive Operator-Valued Measure). By the means of calculating the receiver’s all kinds of proper unitary transformations, teleportation accomplishes with probability.Furthermore, the research on the Cluster state provides a special case to explore the properties of the four-particle entangled state.