Solid-state Quantum Memory For Narrowband Quantum Light Sources

Interface between a quantum state of light and a matter system is a fundamental requirement of constructing a large-scale quantum network based on quantum repeaters,which can overcome the exponential transmission loss of single photons and extend distance of entanglement distribution.Rare-earth-ion-doped crystals?REICs?are attractive candidates for reliable quantum memory of photons owing to their long coherence time and wide bandwidth.Investigation of the solid-state quantum memories includes developing quantum light sources that are compatible to the memory crystals and improving the performance of the memory.In this thesis,we investigate two types of non-classical quantum light sources that are suitable to the specific REICs,Nd³⁺:YVO4 and Pr³⁺:Y₂SiO₅.Moreover,we explore the methods of improving the spin-wave storage efficiency of the Pr³⁺:Y₂SiO₅ crystal.The main results of the thesis are listed as below:1.For the first time,we reveal that the phase mismatching problem emerges in a spontaneous parametric down-conversion?SPDC?process of generating high-dimensional entanglement on the degree of freedom of photonic orbital angular momentum?OAM?when the spectral bandwidth is restricted.This phase mismatching problem is caused by divergence of Languerre-Gauss?LG?modes.We design an annual-ring-type quasi-phase-matching crystal by tracking the divergences of LG modes,which will greatly enhance the dimensionality and improve the quality of the narrowband entangled state.The OAM-entangled state can be stored in the Nd³⁺:YVO4 crystal and may find applications in a qudit-based network.2.We build an ultra-narrowband high-brightness photon pair source using a cavity-enhanced SPDC.The nondegenerate photon pair source has a bandwidth of approximately 2 MHz with a c-band telecom idler photon and a signal photon at the wavelength of 606 nm which is compatible with the quantum memory based on Pr³⁺:Y₂SiO₅.Furthermore,we demonstrate the heralded storage of the signal photons encoded with OAM qubit state.3.We present the first spin-wave atomic frequency comb?AFC?storage of light with a backward retrieval in Pr³⁺:Y₂SiO₅ which can,in principle,overcome the re-absorption problem existed in the forward retrieval configuration.The backward retrieval is realized by applying two counter-propagating control pulses.We also introduce the time-reversal iterations of pulse shape to this solid-state system and observe an improvement of efficiency by using this technique.