量子点和光子晶体微腔耦合体系制备纠缠光子对的研究

The Cavity quantum electrodynamics system based on coupled quantum dot and solid state microcavity provides potential platform for the realization of quantum information processing. A source of entangled photon pairs is a fundamental component of quantum information processing. The cascade decay of the biexciton in a quantum dot can emit photons with orthogonal polarizations. Photonic crystal H1 cavity has polarization entangled mode. The generation of polarization entangled photon pairs with coupled quantum dot and photonic crystal H1 cavity reveals great advantages. However, the precise positon control of the quantum dot in a cavity is technologically challenging but mandatory. This project will propose a movable cavity realized by laser irradiating on photonic crystal slab. With the movable cavity we expect a solution of the problem involving quantum dot position control. The structure design is implemented by Finite-Difference Time-Domain method. And the interaction between light and matter is treated beyond perturbation method by using full quantum theory. Demonstration of the feasibility of the entangled photon pairs produced with this scheme will be provided. Moreover, strong coupled distant H1 cavities connected by photonic crystal waveguide will be designed, aiming at the protection of degeneracy and orthogonal polarizations of the H1 cavity mode. This work is important for the entanglement distribution among distant nodes in a quantum network.

固态微腔与量子点耦合的腔量子电动力学体系是实现量子通讯和量子计算在内的量子信息处理非常有潜力的平台。纠缠光子对是实现量子信息处理的基础单元之一。量子点双激子态的级联辐射可以发射偏振正交的光子，平板光子晶体H1微腔具有偏振正交的简并基态模式。因此，利用量子点与光子晶体微腔耦合制备偏振纠缠光子对显示出巨大的优势。但是在此方案中迫切需要解决量子点在微腔中位置尚不能精确控制的问题。本项目通过时域有限差分计算方法结合全量子理论，提出通过激光照射平板光子晶体实现可移动微腔以解决微腔中量子点位置问题。并证明可以实现纠缠光子对的高保真度制备。更进一步，我们试图实现光子晶体H1微腔基态模式远距离的强耦合，并能够保护其简并性和偏振正交性不受破坏，这对实现远距离纠缠具有基础性意义。

半导体量子点与固态微腔耦合系统是实现量子信息处理的有效平台。得益于目前半导体微纳加工工艺的发展和量子点优异的光学性质，此体系易于加工集成，有利于实现可扩展的量子比特的叠加态和纠缠态。但是，由于半导体量子点的生长方式，导致量子点与微腔的耦合强度难以调控。而可控的量子比特-光子耦合系统是生成单光子源、纠缠光子对源，及进一步实现集成量子信息处理芯片的基础。本项目围绕量子点-微腔耦合强度的可控调节开展了一系列工作：提出了利用一维光子晶体纳米带腔与微盘腔耦合来调节量子点-微盘耦合强度的方案，实现了耦合强度的调节；提出了利用光学回音壁模式实现两个远距离微腔之间强耦合的方案；提出了通过暗态光学回音壁模式实现远距离量子点之间可控的最大纠缠的方案。这些工作为实现量子光学网络提供了可能性方案。