半导体胶体量子点与纳米线微腔的耦合及量子比特扩展的研究

In solid state quantum information processing, scaling-up quantum bits (qubits) is one of the key problems to be solved, which providing the opportunity to achieve the quantum photonic network. So far, highly coherent two-level quantum systems are required to implement solid-state qubits such as single atoms, single excitons and single spins. To implement qubits and single-photon sources, semiconductor colloidal quantum dots have many advantages, such as energy can be easily controlled, ultrafast coherent control, and can be working at room temperature. In this project, we will investigate the coupling between the colloidal quantum dots and semiconductor nanowire/nanobelt cavity, to scale up of quantum bits and achieve a quantum dot-nanowire based photonic network. In detail, we will investigate the luminescent energy levels of colloidal quantum dots and coherent control of the quantum dot qubit to characterize the decoherence time. By controlling the quantum dot and nanowire spatial position precisely, coherent coupling between quantum dots and nanowire will be examined. The coupling mechanism between quantum dots and nanowires will be analyzed both experimentally and theoretically, to reveal the decoherence mechanism of this hybrid system. The single photons from single quantum dots in the nanowire cavity will be detected optically and electrically. The coupling between quantum dots via the nanowire cavity will be investigated to achieve the scaling up of qubits. Finally, we would like to achieve quantum photonic network based on the quantum dot and nanowire hybrid system.

量子比特的扩展是固态量子信息处理重要基础，也是实现量子光学网络的前提，为未来信息技术的发展提供了可能。通常固态量子比特的载体是一个高度相干的二能级单量子态系统，比如单原子，单激子，单自旋等。半导体胶体量子点作为量子比特或者单光子光源的载体主要优点有：能量可控性强、相干控制速度快、可以在室温工作等。本课题主要研究自组装胶体量子点与半导体纳米线微腔的相干耦合及其导致的量子比特的扩展，最终实现一个基于量子点和纳米线耦合的量子光学网络。主要研究内容有：首先研究量子点的发光能级和量子点量子比特的相干控制，测量相干寿命；精确控制量子点与半导体纳米线的位置，研究它们之间的相干耦合，从机理上弄清量子点与纳米线的耦合机制；实现光激发胶体单量子点单光子源在纳米线微腔中的传输及其光、电探测；探索两个或者多个量子在同一根纳米线或者纳米带上的相互作用，以及多量子点量子比特的扩展。

半导体胶体量子点在量子比特以及作为单光子源载体等方面具有明显的优势。通过调节量子点的尺寸、成份以及表面特性等可以控制量子点的发光波长范围。最重要的是，胶体量子点能够在室温下发光。本项目主要分析了胶体量子点的复合机制，发现CuInS2/ZnS 胶体量子点的俄歇效应受温度以及激发功率的影响；研究ZnS纳米颗粒在不同温度下电导率随电压的变化关系以及纳米颗粒的介电常数随温度的变化关系，该纳米颗粒的电输运机制主要来自于Richardson-Schottky机制；分析了ZnO纳米线中的回音壁模式以及GaAsP纳米线的光学特性；通过CuInS2/ZnS胶体量子点与微盘的耦合，发现微盘能够提高量子点的发光效率以及减小量子点的光氧化和光漂白作用。利用微加工技术等制备单量子点或纳米线器件，通过共聚焦显微系统，研究了光场或电场作用下载流子的复合机制、输运行为以及半导体量子点与光学微腔、光子晶体微腔耦合的光学性质。这对于实现固态量子信息处理及量子比特扩展的研究具有重要的意义。在项目的资助下，总共发表SCI论文13篇，EI论文1篇，其中包括Appl. Phys. Lett. 3篇，Optics Express 1篇，Nano Letter 1篇，AIP Advances 1篇，Chin. Phys. Lett. 1篇，Scientific Reports 3篇，ACS Photonics 1篇，Nano Research 1篇，《物理学报》1篇，《物理》1 篇。