Crystal Growth And Optical Memory Based On Rare Earth Chloride

The rapid development of the quantum information in recent years requires many new technologies such as new materials and equipments.Quantum communication requires quantum storage materials and entanglement sources that match the memo-ry.Solid materials containing rare earth ions have gradually become one of the most promising materials for realizing quantum storage,due to their advantages of long stor-age time and large bandwidth among many candidate systems for quantum storage.This paper presents the author's research on the growth of stoichiometric rare-earth crystals,and their spectroscopic investigation and applications in optical storage,obtaining high-energy laser pulses from continuous wave laser using optical cavity,the construction of entanglement source matching with quantum memories.The main re-sults are as follows:1.Growth and spectroscopic investigation of NdCl₃·6H₂O crystal.NdCl₃·6 H₂O has a very narrow optical inhomogeneous linewidths.Its extreme-ly high color center concentration and strong interaction between rare earth ions n-able potential applications in quantum storage and computing.Since the Nd3+ ion is a Kramers ion,there is a strong interaction between ions in the NdCl₃·6H₂O crystal.We grow NdCl₃·6 H₂O single crystals and perform optical absorption and emission spectroscopy of this material.We study the polarization-dependent properties of the Nd3+ ion's 4I9/2?4F3/2 transition,and discuss the effects of non-radiative transitions in this crystal.2.Optical storage based on EuCl₃·6 H₂O crystal.The isotope-purified EuCl₃·6H₂O crystal has shown a inhomogeneous broaden-ing below the energy level spacing.We grow EuCl₃·6 H₂O single crystal,and obtain the coherence time of its 7F0?5D0 transition is 55.7 ?s.We realize the atomic fre-quency comb optical storage with a efficiency of 1.71%at a storage time of 1 ?s.The line shift of 7F0?5D0 depending on the sample temperature is analyzed.3.Laser pulse amplification based on optical resonator.In the experiments of quantum storage,a continuous wave laser with a narrow linewidth and stable frequency is usually required.However,some applications(such as optical ? pulses)require short-time high-power laser pulses.It is difficult for ordinary continuous wave lasers to output short pulses with extremely high power density.We propose and implement a scheme to use an optical cavity to convert continuous-wave laser into high-power-density pulsed light.Our device enables pulse amplifying of 17 times with an adjustable pulse width.4.Building a parametric down-conversion entangled light source matching with quantum memories.In addition to quantum memory,a complete quantum repeater scheme also re-quires entangled photon pairs and entanglement swapping.We use waveguide PPKTP to achieve high-brightness down-conversion photon pairs,and use optical etalons to match the entangled photon bandwidth with the memory.The method of linear optics and post-selection is used to achieve the preparation of the maximum entangled state.5.Software development.Computer software closely related to the experiment is developed to simplify cer-tain calculation processes in the experiment or to achieve the special operating require-ments of certain instruments.These softwares include:Gaussian optical parameter calculation program to simplify beam waist calculation;TED4015 temperature con-trol software to realize programmable temperature control;TimeTagger time-to-digital converter software that can flexibly use the virtual channel function;cryostat magnet software controlled by analog signal.