Research On Two Key Technologies In Quantum Communication

Quantum communication is an important element of quantum information.Quantum communication uses quantum states to transmit classical information,and the security and efficiency of quantum communication have been greatly improved compared with classical communication due to the quantum characteristics of quantum states.Quantum Teleportation and Quantum Key Distribution are two key technologies of quantum communication.Quantum Teleportation uses quantum channel and classical channel to complete the transmission of unknown quantum states,which has the value of safe and efficient application;while quantum key distribution uses quantum states for key distribution,which has theoretical unconditional security and greatly improves the security of communication.Therefore,the key technology in quantum communication has certain research value.The following is the main work of this thesis.1?For the current Quantum Teleportation protocols mainly use a specific quantum entangled state to transmit quantum states,which makes different Quantum Teleportation protocols incompatible with each other,and the quantum entangled state used in the Quantum Teleportation may not be equal to the Schmidt rank of the transmitted quantum state,which leads to the difficulty of establishing the correspondence between the projection measurement basis and the unitary transform.The quantum Fourier transform based Quantum Teleportation protocol for transmitting arbitrary quantum states as a quantum channel is proposed.In the protocol,it is assumed that the Schmidt rank of the quantum entangled state is greater than or equal to the Schmidt rank of the quantum state being transmitted,and the quantum Fourier transform is used to make the communication parties get the appropriate projection measurement basis and the corresponding unitary transformation to complete the transmission of the quantum state.The general equations of the projection measurement basis and the corresponding unitary transform are derived,and a general comparison table of the projection measurement basis and the corresponding unitary transform is given;the security of the protocol is analyzed,and the applicability of the protocol is demonstrated by comparing with other Quantum Teleportation protocols.2?To address the problem that the actual devices are not always perfect in the actual Continuous Variable Quantum Key Distribution system and the existing errors may affect the actual security performance of the system,this thesis investigates the impact of the appearance of imperfect phase modulation on the performance of the Continuous Variable Quantum Key Distribution system in the Gaussian modulated coherent state Continuous Variable Quantum Key Distribution system.By analyzing the actual performance of the system based on the modulation noise model and the channel noise model,it is found that the generation of imperfect phase modulation will degrade the system performance,and the correct judgment of the noise source and the selection of the correct noise model can passively improve the system performance.The method to determine the source of noise and two compensation schemes to actively enhance the system performance are also designed,and the characteristics of the two active compensation schemes and the corresponding applicable scenarios are analyzed.