量子点与热原子系综混合量子系统的研究

The hybrid quantum system is an important research direction and frontier problem in quantum information. This project is aiming to study atom-quantum dot hybrid quantum system. On one hand, we prepare a single-photon source from the frequency tunable quantum dot at 780 nm. Firstly, AlGaAs quantum dots are fabricated by droplet epitaxial method. Then the quantum dots are transferred to a piezo substrate. Frequencies of photons from quantum dots can be fine adjusted via the voltage control. Through electron-beam lithography and precise positioning by photoluminescence imaging, the quantum dots are deterministically coupled with nanophotonic structures, such as microlenses, micropillars and bull's eye gratings, from which we find the most suitable method for enhancing the coupling efficiency. On the other hand, two-photon pairs are generated from spontaneous four-wave-mixing in hot Rb vapor. Driven by two vertically polarized counter-propagating pump laser and coupling laser beams, phase-matched and backward Stokes and anti-Stokes photon pairs are spontaneously generated from a paraffin-coated hot Rb vapor cell, based on which, a heralded single-photon source is prepared. We will also study the saturation absorption and phase-locked loop frequency-locking. Finally, two-photon interference of two systems is completed to realize quantum integration of two different quantum physical systems.

混合量子系统是量子信息中的重要研究方向和前沿问题。本项目是关于量子点与热原子系综混合量子系统的研究。一方面，制备频率可调量子点单光子源。首先使用液滴刻蚀外延生长制作发光波长为780nm的AlGaAs量子点。利用薄膜转移技术，将量子点转移到压电陶瓷基底上。通过电压控制，实现对量子点发光频率的精细调节。结合电子束直写工艺，确定性的将量子点与微透镜、柱形微腔或牛眼光栅等微纳结构耦合。探究最适合频率可调量子点发光增强的方法。另一方面，搭建基于铷热原子蒸汽池的自发四波混频系统。其中泵浦光与耦合光共线，且反向入射到石蜡涂层热铷原子蒸汽池，使用单模光纤接收相位匹配自发四波混频产生的斯托克斯和反斯托克斯光子对。在此基础上制备宣布式单光子源。研究饱和吸收法或锁相环锁频技术。最后，完成两个系统单光子的量子干涉，通过单光子探测器、时间分析仪分析三个光子符合信号。真正实现两个不同物理体系组成的混合量子系统。

混合量子系统是量子信息中的重要研究方向和前沿问题。本项目在量子点、热原子系综和非线性光学系统三种量子系统进行研究。首先，制备频率可调量子点单光子源。首先使用液滴刻蚀外延生长 制作发光波长为780nm的AlGaAs量子点。其次，搭建基于铷热原子蒸汽池的自发四波混频系统。其中泵浦光与耦合光共线，且反向入射到石蜡涂层热铷原子蒸汽池，制备四波混频光源，输出波长分别为780nm和776nm。第三，根据热原子系统特性，提出了利用热原子折射率增强实现平行世界光学模拟。第四，几种典型的周期极化非线性材料中的各种准相位匹配过程进行了分析和计算。提出了一种在单片材料中实现多种准相位匹配的通用方法。讨论了一种基于 Sagnac 干涉仪制备多个纠缠光子对的新颖设计。