Solid State Quantum Networks (SSQN)

量子通信，即量子叠加态的远距离传输，由于不可避免的光子吸收损失，目前被限制在约200公里(光纤和自由空间中)。为此，已经建立了利用“纠缠交换”和“隐形传态”来延长这一距离的理论方案。通过级联短纠缠交换子段，原则上可以在非常长的距离上产生纠缠(相关)比特，比特率仅受一个短段中的损耗的限制。如果实现这一点，将把量子通信应用，如量子密码学和量子隐形传态扩展到数千公里的距离。在这个联盟中，我们提议致力于建立这样一个基于半导体量子点-微柱腔系统的确定性量子网络。我们将从量子点(QD)的双激子-激子级联中产生纠缠光子源，其潜在保真度为&gt；90%。此外，我们还将开发一个QD自旋微柱腔系统，它可以作为一个一体化的自旋光子接口和贝尔态分析器。该组件消除了两个光子同步到达的需要，并允许在自旋相干时间(微秒到毫秒)的时间尺度上执行等待成功协议。更多的子组件将包括电光可调谐单光子源和最近提出的顺序纠缠源。有了这组子组件，我们将能够实现可扩展量子网络所需的所有功能，包括最终的纠缠净化步骤。这与之前的纠缠交换(和隐形传态)的实验演示形成了鲜明的对比，这些实验演示是概率的，因此是不可扩展的。该项目涉及四个合作伙伴之间的合作。我们将汇集两个世界级的小组，LPN和Würzburg(UWUERZ)，致力于生产高效纠缠对源(LPN)的微柱腔，以及强耦合QD自旋腔系统(UWUERZ)，目的是解决纠缠对源和自旋腔系统的挑战性问题。新的和实用的纠缠方案将由帝国理工学院(IMP)提供理论支持，实验实施将由布里斯托尔(BRIS)和LPN进行，他们在量子光通信、QD自旋和半导体微腔量子电动力学方面拥有世界级的专业知识。

Quantum communication, the transfer of quantum superposition states over long distances, is presently limited to about 200km (both in optical fibre and free space) due to unavoidable photon absorption losses. For this reason, theoretical schemes to extend this distance using "entanglement swapping" and "teleportation" have been established. By concatenating short entanglement swapping sub-sections it is in principle possible to generate entangled (correlated) bits over very long distances with bit rate only limited by the losses in one short section. If realised this would extend quantum communication applications such as quantum cryptography and quantum teleportation out to distances of thousands of kilometres.In this consortium we propose to work towards such a deterministic quantum network based on semiconductor quantum dot-micropillar cavity systems. We will generate entangled photon sources from the biexciton-exciton cascade of a quantum dot (QD), with a potential fidelity of >90%. Moreover, we will develop a QD-spin micropillar cavity system, which acts as an all-in-one spin-photon-interface and a Bell-state analyser. This component eliminates the need for synchronous arrival of the two photons, and allows a wait-until-success protocol over the timescale of the spin coherence time (microseconds to milliseconds). Further subcomponents will include electro-optically tuneable single photon sources and recently proposed sequentially entangled sources.With this suite of subcomponents we will be able to realise all the functions required for a scalable quantum network including the final entanglement purification steps. This is in contrast to previous experimental demonstrations of entanglement swapping (and teleportation) which were probabilistic and thus unscalable.The project involves collaboration between four partners. We will bring together two world-class groups, LPN and Würzburg (UWUERZ), working on micropillar cavities producing highly efficient entangled pair sources (LPN), and strongly-coupled QD-spin-cavity systems (UWUERZ), with the aim of addressing the challenging issues of entangled-pair sources and spin-cavity systems. Theoretical support for novel and practical entanglement schemes will be provided by Imperial College (IMP), and the experimental implementation will be performed by Bristol (BRIS) and LPN, who have world-class expertise in quantum optical communication , QD spins and semiconductor microcavity quantum electro-dynamics.