Research On Key Technologies Of Quantum Entanglement Interconnection

The quantum information technology,with the help of quantum physical resources,can provide people with information acquisition,transmission,and processing technology that goes beyond classical physics.Its ultimate goal is to establish a quantum network or quantum internet.One of the key tasks in realizing a quantum network is to complete the transmission of quantum information between different quantum nodes.Currently,the fidelity,distance,and capacity of quantum information transmission are still challenges that restrict the practical application of quantum networks.This dissertation combines the implementation of the “Experimental Research on Frequency Multiplexed Quantum Channel in Telecommunication Band” project of the National Key R&D Program of China to conduct research on key technologies of quantum entanglement interconnection.Based on this,high-speed metropolitan quantum teleportation and multi-spectral quantum teleportation with quantum storage have been realized,with the aim of promoting the development of quantum networks towards practicality from the perspective of quantum information transmission.A theoretical model of the quantum teleportation system based on spontaneous parametric down-conversion entangled light source and weak coherent single-photon source is established.The system’s key parameters are optimized,and the system’s comprehensive performance is improved,laying a good foundation for subsequent experimental research.Based on the campus fiber network of the University of Electronic Science and Technology of China,the metropolitan quantum internet research platform-“Ginkgo No.1” has been built to conduct experiments on metropolitan quantum teleportation.Based on the cascaded second-order nonlinear optical process,a high-performance time-bin quantum entangled light source at telecom band has been developed.Using the decoy state method,high-repetition time-bin qubits have been prepared.An automated photon indistinguishability measurement and control system is designed and built to improve the photon indistinguishability after long-distance fiber transmission.Based on the above key technologies,the teleportation rate has been increased to the level of Hertz-7.1±0.4 Hz when the quantum state transfer distance is 64 km,and the single-photon fidelity of quantum teleportation is measured to be 90.6±2.6%.To further improve the teleportation rate,the wide-spectrum characteristics of the spontaneous parametric down-conversion process and the narrow-band tunable filter technology are fully utilized to realize multi-spectral quantum entangled light source and Bell state measurement.Multi-spectral quantum teleportation experiments have been carried out.When the equivalent transmission distance of the quantum state is 50 km,the total teleportation rate reaches 148.0±3.2 Hz,and the average fidelity is 82.0±0.6%.Towards the quantum repeater in the quantum network,based on the atomic frequency comb protocol,a multi-spectral light-atom entanglement interface is successfully prepared in the erbium-doped fiber quantum storage,and the typical twophoton Franson interference fringe visibility is measured to be 77.2±2.7%.Furthermore,using the ultra-large bandwidth characteristics of the erbium-doped fiber quantum storage,combined with the multi-spectral light-atom entanglement interface,the 5-spectral quantum teleportation with quantum storage is demonstrated.When the quantum state transfer distance is 6.4 km,the average teleportation fidelity is 74.2±0.5%.