光学微腔对单量子点中自旋的读出与调控

Due to the long lifetime and coherence time, spin qubits in single semiconductor quatum dots have attracted lots of interests for solid-state quantum compuation. In the mean time, photons as flying qubits have been investigated in the last two decades for optical quantum information processing. Combining the spin (stable) qubits and photon (flying) qubits is a key issue to achieve the quantum photonic network. Previously, We have demosnstated the precise control of single charge and spin in single quantum dots by applying an external electric or a magnetic field. In this project, we are investigating the photonic crystal waveguide heterojunction integrating with single quantum dots, reading out the polarization of single photons selectively by the waveguides. Designing and fabricating single quantum dot coupled with photonic crystal cavity system, examining the polarization of cavity modes with single quantum dots exciting from different position in the cavity, and reading out the polarization of the emitted photons via cavity mode. Finally the single spins are initialized by an external exectric field or a magnetic field to form a spin polarized charged exciton states, a three-level system. Then the spin polarzied excitonic states are tuned to resonant with the cavity mode by Zeeman effect or temperature, interactions between spin polarization and the cavity photon are investigated to realize the spin-photon interface, and potentially scaling them up in the photonic waveguide.

半导体量子点中单自旋由于其具有较长的自旋寿命和退相干时间一直是近年来固态量子比特的主要研究对象之一，同时光子作为飞行量子比特一直是信息传输的主要途径，结合两者的优点实现固态量子比特和飞行量子比特界面是实现可扩展化量子光学网络的关键。本项目在前期利用电场和磁场在单个量子点中实现了单个自旋高精度初始化和探测的基础上，设计非对称性的光子晶体波导异质结，通过单量子点发光与光子晶体波导的耦合实现对所发射单光子自旋极化进行选择性读取；设计并制备量子点耦合的光子晶体微腔，通过调控单量子点在微腔中的位置实现不同的偏振的偶极子与不同微腔模式耦合，从而实现自旋极化的确定性读出；利用电场或者非共振激发形成的带电激子态，在磁场作用下形成两组自旋相反的三能级系统，利用光子晶体微腔与自旋极化的带电激子能级的强相互作用实现光子对单个自旋态的相干操控，从而形成一个自旋-光子界面，并探索其集成到光子晶体波导中的可扩展性。

量子点具有丰富的分立能级，可以作为自旋量子比特的载体。通过与光学波导、微腔的耦合，可以实现自旋-光子界面，这是实现固态量子比特和飞行量子比特相干耦合的关键，对未来量子信息领域的发展具有十分重要意义。本项目利用共聚焦荧光光谱和光电流谱研究了自组织生长InAs量子点的光电特性，通过外加电场和磁场实现了对单量子点中的电荷及其自旋的标定，观测到了单量子点的暗激子态，同时通过改变磁场实现了对单量子点隧穿速率的调节，通过双色共振激发在带电激子态中发现了库伦作用诱导产生的光电流巨大增益现象，并标定了不同激子态空穴和电子的g因子张量；研究了InP纳米线中晶相量子点不同激子态的磁光特性，得到了激子态电子和空穴的g因子张量；研究了光学波导与量子点的手性相互作用，实现了不同自旋态的单向传输与读出；研究了光子晶体L3型微腔与量子点的耦合体系，首次实现了双光子拉比劈裂；同时在p壳层激子与微腔的耦合体系中实现了对耦合强度的增强和调控；研究了耦合微盘腔的光学特性，实现了有源腔的diabolical points（DP）；研究了拓扑光子晶体微腔与量子点的相互作用，实现了基于拓扑角态的低阈值激光及其与单量子点的弱耦合。在项目资助下，共发表SCI论文10篇，其中包括Physical Review Letters 2篇，Laser & Photonics Reviews 1篇，Light: Science & Applications 2篇，Applied Physics Letters 1篇，Physical Review Applied 3篇，Advanced Quantum Technologies 1篇。