Quantum Dot Spin State Tailoring for Scalable On-Chip Quantum Information Processing

基于固态自旋量子位的容错量子计算机的成功实现很可能涉及到它们在规则晶格中的排列。最近的技术突破使这种可扩展量子系统的创建成为可能，其中最突出的是现场控制量子点平台。这些量子发射体的高光谱质量、确定性定位和长寿命自旋的全光超快寻址能力，使它们成为量子硬件平台的非常有吸引力的候选者。虽然有几个建议试图解决非均匀扩展的问题，以便在这样的硬件中实现可扩展的交互，但在这里，我们将重点关注一种新的混合方法的特殊需求，该方法使用微腔极化子作为信息总线。这种方法是基于量子点中自旋极化激子与自旋之间的自旋依赖相互作用。因此，为了使这种方法起作用，有必要设计自旋态，以便在混合系统中存在自旋-自旋相互作用，同时保持量子比特的光学寻址能力。在这个项目中，我们将通过一系列相干控制实验来研究带电量子点中捕获自旋态的各种按需工程方法，这些实验将探索不同方法如何影响全光操作的通用单量子比特门的性能。我们将首先研究的样品是用delta掺杂进行充电的自组装InGaAs量子点，而在后期阶段，我们将研究衬底纳米图案和纳米压印光刻现场控制的量子点，由我们的国内和国际合作者提供。基于我们的门的性能和对我们将从这个项目中获得的局限性的理解，我们将与专门从事这种纳米结构生长的国内和国际合作者密切合作，为优化的混合极化量子点系统设计一系列混合样品。因此，该项目将为实现可扩展的片上量子信息处理的新型混合方法奠定基础。这个实验性很强的项目将有助于开发具有相干控制能力的磁波谱实验。利用这种装置，我们将通过在液氦温度下的高分辨率磁谱研究来解决和表征自组装和位置控制的量子点样品，而对于通用单量子比特量子门的性能表征，工作将涉及利用脉冲和连续波激光组合的先进全光自旋控制技术。

A successful implementation of a fault tolerant quantum computer based on solid state spin qubits will most likely involve their arrangement in a regular lattice. Recent technological breakthroughs have enabled the creation of such scalable quantum systems with one of the most prominent being the platform of site-controlled quantum dots. The high spectral quality, deterministic positioning and all-optical ultrafast addressability of long lived spins in these quantum emitters, make them very attractive candidates as a platform for quantum hardware. Although there are several proposals that attempt to address the issue of inhomogeneous broadening in view of enabling scalable interactions within such hardware, here we will focus on the particular needs of a new hybrid approach that uses microcavity polaritons as a bus for information. This approach is based on spin dependent interactions between spin polarized exciton polaritons and the spins in quantum dots. For this approach to work, it is therefore necessary to engineer the spin states so that there are spin-spin interactions in the hybrid system while also maintaining optical addressability of the qubits. In this project we will investigate various approaches for on-demand engineering of the trapped spin states in charged quantum dots through a series of coherent control experiments that will explore how the different approaches affect the performance of all-optically operated universal single qubit gates. The samples that we will investigate initially are self-assembled InGaAs quantum dots with delta doping for charging while at a later stage we will investigate substrate nanopatterned and nanoimprint lithography site-controlled quantum dots, provided by our national and international collaborators. Based on the performance of our gates and the understanding of the limitations that we will gain from this project, we will then design a series of hybrid samples for an optimized hybrid polaritonic quantum dot system working closely with our national and international collaborators that specialize in the growth of this type of nanostructures. This project will therefore lay the groundwork for the realization of the novel hybrid approach for scalable on-chip quantum information processing. This heavily experimental project will contribute towards the development of a magnetic spectroscopy experiment with coherent control capabilities. Using this setup we will address and characterize both the self-assembled and site-controlled quantum dot samples by means of high resolution magneto-spectroscopic studies at liquid helium temperatures, while for the characterization of the performance of the universal single qubit quantum gates the work will involve advanced all-optical spin control techniques utilizing a combination of pulsed and CW lasers.