Research On Quantum Secure Communication And Its Circuit Simulation

Quantum communication provides a new way for securely transmitting secret message. Despite of the computational ability of the eavesdropper, the security of quantum communication is only guaranteed by the fundamental laws of quantum mechanics. Quantum communication has native advantage in the sense of security and it has gradually developed into a very important subject in the field of quatum information.The contributions of this dissertation are mainly on the design of the protocol of quantum communication and its circuit simulation. The content of this dissertation includes four areas in quantum communication, i.e. quantum key distribution (QKD), quantum secure direct communication (QSDC), quantum teleportation, qantum circuits for implementing quantum communication. The details are as follows:In the field of quantum secure direct communication, we propose a novel controlled quantum secure direct communication with quantum encryption via partially entangled GHZ state. Under the supervision and help of the third side, the sender and the receiver can securely share the private quantum entanglement keys used to encrypt and decrypt the secret message. According to the results of checking eavesdropping on the decoy photons, communicators can decide whether the quantum keys are reused in the next round. Generally, any eavesdropping will inevitably disturb the states of the decoy photons and be detected. Additionally, the arbitrary transmission error can be corrected in the process of the protocol.In the field of quantum teleportation, we propose a protocol for the exact teleportation probabilistically (with unit fidelity but certain probability of failure); a protocol for the entanglement teleportation which transfers not only the encoding messages but also the entanglement structure; a controlled protocol for the teleportation. In addition, we investigate the relation between transformation operator and the quantum channel for realization of the quantum teleportation.The circuit simulation is instructive for the realization of the quantum communication. We do research on the model of quantum circuit and propose two efficient quantum circuits to implement the protocols for quantum communications. One is that we propose a protocol for quantum secure direct communication via W state and design its quantum circuit by means of decomposing the unitary operation into universal quantum logic operation. The other is that by decomposing the process of state evolution from the initial states to the final states, the quantum circuits for the generalized measurement described by positive operator-valued measure (POVM), which is utilized to probabilistically distinguish the two non-orthogonal states, are explicitly constructed. The efficient quantum circuit for implementing the protocol for teleportation is also provided.