Researches On Schemes For Quantum Teleportation And Quantum Information Splitting

Quantum cryptography is the combination of quantum mechanies and clas-sical cryptography. Compared with classical cryptosystems, quantum cryptosys-tems have two representative advantages. One is the provable security(even un-conditional security) and the other is the eavesdropping detectability. Therefore,quantum cryptography has inherent advantage in the sense of security and it hasgradually developed into an important branch of modern cryptography. It is im-plied by the research both in experiment and in theory that quantum cryptographywould grow up in the next generation of technologies in cryptography.The contributions of this dissertation are mainly on the design and analysisof the schemes for quantum cryptography, including quantum teleportation (QT),quantum information splitting (QIS) and quantum entangled swapping (ES). Thedetails are as follows:With respect to the design, we mainly propose two QIS schemes.1. One is the QIS of an arbitrary N-qubits state (where N is a natural number)via using a complicated qubit state as quantum communication carrier which iscomposed of a three-qubits GHZ-like entangled state and (N1) sets of EPRpairs. It is shown that this scheme can be faithfully realized by performingBell state measurements (BSMs), single qubit measurements (SMs) and localunitary operations (LUOs). The presented scheme is efcient, economical,feasible.2. Using the generalized seven-qubits Brown state as quantum communicationcarrier we successfully fnish the schemes for QT and QIS of arbitrary single,two and three qubits states, respectively. With a discussion of the resourcenecessary we make an overall analysis among these diferent proposals andpresent a principle of almost even distribution of particles between sender andcontrollers. It can be judged which proposal is the best one. Moreover, weshow a conjecture about QIS of an arbitrary N-qubits state via the generalized(2N+1)-qubits Brown state.As for security analysis, we only analyse the frst scheme which is similar tothe second one. Our schemes can be against external eavesdropping and internalparticipants attacks. This analysis can be also used to other similar schemes.