Quantum interface engineering with solid-state spins and photons

该项目属于EPSRC“量子技术”研究领域的福尔斯。该项目侧重于实验量子通信技术，特别是使用III-V量子点（QD），这些量子点被广泛认为是量子光网络中使用的领先量子节点候选者之一。它将研究新一代的晶格匹配的GaAs量子点，这有望在自旋量子位（量子位）的相干性相对于自组装InGaAs量子点的最新技术水平的重大改进。总体目标是证明它们可以作为量子网络节点，这需要同时显示：高效光子收集，量子位控制和核量子存储器。这将允许从量子点产生光子，这些光子与其固态自旋量子比特纠缠足够长的时间，以便它们可以用于与其他量子节点联网以实现量子网络。最初的重点将是改善量子点中的自旋量子比特与出射光子之间的光学接口。增强光子收集效率是至关重要的，因为虽然GaAs QD在其长自旋相干时间（用于保持量子态的重要度量）方面显示出很大的前景，但它们在光子收集效率方面落后于其他QD候选者（例如InGaAs）。其愿景是将量子发射器（QD）放入光子微腔中，这将增强发射和耦合到光纤模式中以进行长距离传输。接下来，我们将演示量子点电子自旋的量子位控制，这将是全光学的。这种有效光学界面内的自旋控制组合将是独特的，并且将允许概念验证演示，例如确定性光子-光子量子门。最后，量子存储器将通过利用单电子和近端核自旋之间的超精细相互作用来实现，以促进使用电子的光学可寻址存储器，使这种基于量子点的量子节点具有专用的量子存储器。该项目旨在提供形成量子通信和计算网络骨干的多种量子协议的基准测试结果，例如光子量子比特之间的量子门，量子中继器状态的生成以及纠缠的分发和存储。实现可行的量子光网络将使量子节点之间实现真正的量子互联网，为完全私有的通信（由量子力学原理确保），量子密码学和分布式量子计算铺平道路。这项工作是与剑桥大学的量子光学材料和系统小组、约翰内斯开普勒大学林茨的半导体物理小组和牛津大学的光子纳米材料小组合作进行的。

This project falls within the EPSRC "quantum technologies" research area. The project focuses on experimental quantum communication technologies, using in particular III-V quantum dots (QDs), which are widely considered to be amongst the leading quantum node candidates for use in quantum optical networks. It will investigate a new generation of lattice-matched GaAs QDs, which promise a major improvement in the coherence properties of spin quantum bits (qubits) relative to the state of the art in self-assembled InGaAs QDs. The overall objective is to demonstrate that they can serve as a quantum networking node, which requires showing simultaneously: high-efficiency photon collection, qubit control, and a nuclear quantum memory. This will allow the generation of photons from the QD which are entangled with its solid-state spin qubits for a sufficient time that they can be used to network with other quantum nodes to realize a quantum network.Initially the focus will be on improving the optical interface between the spin qubits in the QDs and the outgoing photons. Enhancing photon collection efficiency is crucial, as while GaAs QDs have shown great promise in terms of their long spin coherence times, an important metric for preserving the quantum state, they lag other QD candidates (e.g. InGaAs) in terms of photon collection efficiency. The vision is to place the quantum emitter (QD) into a photonic microcavity, which would enhance emission and coupling into a fibre mode for long distance transmission. Next, we will demonstrate qubit control of the QD electron spin, which will be performed all-optically. This combination of spin control within an efficient optical interface will be unique, and will allow proof-of-concept demonstrations such as a deterministic photon-photon quantum gate. Finally, a quantum memory will be made possible by capitalizing on the hyperfine interaction between the single electron and the proximal nuclear spins to facilitate an optically addressable memory using the electron, enabling this QD-based quantum node to have dedicated quantum memories. The project aims to deliver benchmarking results on a multitude of quantum protocols forming the backbone of a quantum communication and computing network, such as quantum gates between photon qubits, generation of quantum repeater states, and distribution and storage of entanglement. Realizing a viable quantum optical network would enable a truly quantum internet between quantum nodes, paving the way for fully private communications (ensured by the principles of quantum mechanics), quantum cryptography, and distributed quantum computing. The work is performed in collaboration with the Quantum Optical Materials and Systems group at the University of Cambridge, the Semiconductor Physics group at Johannes Kepler University Linz, and the Photonic Nanomaterials Group at the University of Oxford.