Research On Solid-State Optical Quantum Memory At Telecom Band Based On Erbium Doped Fiber

Quantum networks play an essential role in the field of quantum information,including quantum communication,quantum computing,and quantum precision measurement.Building quantum network currently faces many challenges,one of which is the effective distribution of entangled flying qubits to different quantum nodes and their coversion into stationary qubits to achieve entanglement between these nodes.Typically,quantum memories are used as these stationary qubits.This dissertation aims to develop high-performance quantum memories for long-distance quantum networks under the implementation of the National Key R&D Program,"Experimental Research on Frequency Multiplexed Quantum Channels in Telecommunication Band",which focuses on solid-state optical quantum memories at telecom band with large capacity based on erbium doped fiber（EDF）for promoting the development of quantum networks from the key quantum devices.To investigate the impact of phonons on the optical coherence properties of Er³⁺ions in EDF,we systematically analyze the optical properties of EDF under dilution-refrigeration temperature.At a temperature of 10 mK,we simultaneously measure terahertz-wide inhomogeneous broadening and hundred microsecond-long optical coherence time,in which the optical coherence time reaches 106.15±1.08μs with an inhomogeneous broadening exceeding 2 THz.We measure the excited state lifetime to be10.92±0.61 ms and the Zeeman sublevel lifetime to be 17.79±3.91 s.These results lay the foundation for solid-state quantum memory based on EDF.Based on a thorough understanding of the optical properties of EDF,we further build experimental platform for solid-state quantum memory at telecom band,and use multiple storage metrics to comprehensively evaluate the storage performance of EDF-based quantum memory.The storage time,efficiency and bandwidth are characterized by storing weak coherent light at single-photon level;the storage fidelity is measured by storing time-bin qubit;the preservation of correlation/entanglement characteristics is explored by storing heralded single photons and energy-time entangled photons.The longest storage time of EDF-based quantum memory is 230 ns;the highest storage efficiency is 2.25±0.02%;the available bandwidth is greater than 100 GHz;and the storage fidelity is up to 99.90±0.08%.Towards a high-speed quantum network,we demonstrate a telecom-band quantum memory with large multimode capacity.Aiming at the broadband characteristics of EDF,we propose a scheme for preparing multi-channel atomic frequency combs（AFC）by using optical frequency combs.Five AFCs with a bandwidth of 10 GHz and a channel spacing of 5 GHz are prepared using this scheme.Combined with the intrinsic temporal multimode capability of AFC,330 temporal modes are stored in each AFC,and finally a total of 1650 modes are simultaneously stored.In addition,using the above-prepared five AFCs,five-channel energy-time entangled source is simultaneously stored,leading to constructing a broadband spectrally multiplexed light-matter interface.Finaly,we verify entanglement characteristic of the light-matter interface through Franson interference and CHSH inequality.