Materials World Network: Spin entanglement using transient electrons in C and Si-based materials

纠缠是量子力学中最深刻的概念之一，它在真实材料中的实现需要对态的准备、相干、耦合和测量进行特殊的控制。合作者已经开始在不同的材料中利用电子和核自旋自由度的互补优势来解决这些个别挑战，取得了显著的成功，包括在核自旋中相干存储电子自旋态以实现几秒的相干时间，以及高保真地实现电子和核自旋的真正纠缠。在这个提议中，我们将把这些单独的组件结合在一起，利用光激发分子和硅基器件等系统中电子自旋的瞬变性质，以调解多个核自旋之间的纠缠。除了在固态中提供新兴量子技术的关键组成部分外，这将导致对不同环境和过程下电子和核自旋态退相干背后的机制和关联的新的理解。这一提议的关键思想是利用某些材料和器件中的瞬时电子自旋，不仅理解和克服自旋退相干机制，而且还调解多个核自旋的纠缠。通过实验、密度泛函理论和开放量子系统的模拟，我们将解决各种凝聚态系统中自旋退相干背后的长期存在的问题，以及新出现的问题，如纠缠态的演化和破坏。我们将进一步解决与技术相关的问题，如界面对半导体器件中自旋相干性的影响，以及电子自旋的移除或添加(通过光学或电学手段)对耦合核自旋相干态的影响。六名研究生和博士后将参加牛津大学、赫里奥特-瓦特大学和普林斯顿大学之间的一项激动人心的国际合作，参与机构之间年轻研究人员的流动交流，以及与世界各地的合作者的互动。项目合作伙伴将继续在他们的实验室接待与这项研究计划有关的暑期项目的本科生。牛津大学和Heriot-Watt团队将继续参与增进公众对科学的理解，例如，在皇家学会夏季展览上展示工作，并在他们的实验室接待当地高中生。牛津大学的研究人员有制作一系列获奖视频播客的经验，这次合作将在这一经验的基础上制作一系列联合播客，面向普通观众，描述这一提议背后的基础科学及其承诺的令人兴奋的应用。拨款将支持和加强普林斯顿大学、牛津大学和赫里奥特-瓦特大学研究人员之间现有的、非常成功的合作。这两个小组在执行实验和开发技术方面有着良好的记录，这些技术激励和支持了这里提出的研究。研究人员汇集了一系列专业知识，包括磁共振(ESR，Endor)、量子信息理论、密度泛函理论、半导体物理和有机化学。这项拟议活动的协作性质使人们能够把重点放在跨越各种物理量子自旋系统的基本物理问题上，从而增加实验的影响和科学界的受益者范围。最后，这三个机构的互补仪器提供了这一具有挑战性的实验计划所需的一套必要的实验工具。

Entanglement is one of the most profound concepts to emerge from quantum mechanics, and a phenomenon whose implementation in real materials requires exceptional control over state preparation, coherence, coupling and measurement. The collaborators have already begun to address these individual challenges using the complementary advantages of both electron and nuclear spin degrees of freedom in a diverse range of materials, with notable successes including the coherent storage of the electron spin state in the nuclear spin to achieve coherence times of several seconds, and the true entanglement of an electron and nuclear spin with high fidelity. In this proposal, we will bring together these individual components, exploiting the transient nature of the electron spin in systems such as optically-excited molecules and silicon-based devices, in order to mediate entanglement between multiple nuclear spins. In addition to providing a key component of emerging quantum technologies within the solid state, this will lead to a new understanding of the mechanisms and correlations behind decoherence of electron and nuclear spins states, under different environments and processes.The key idea in this proposal is to use the transient electron spins in certain materials and devices, not only to understand and overcome spin decoherence mechanisms, but also to mediate the entanglement of multiple nuclear spins. Through experiment, density functional theory and modeling of open quantum systems, we will address long-standing questions behind spin decoherence in various condensed matter systems as well as new emerging questions such as the evolution and destruction of entangled states. We will address further technologically relevant questions such as the effect of interfaces on spin coherence in semiconductor devices, as well as the effect of removal or addition of an electron spin (by optical, or electrical means) on the coherent state of coupled nuclear spins. Six graduate students and postdocs will participate in a stimulating international collaboration between Oxford, Heriot-Watt and Princeton, supported by the fluid exchange of young researchers between the participating institutions, as well as interactions with their collaborators around the world. The project partners will continue to host undergraduate students in their laboratory on summer projects connecting with this research proposal. The Oxford and Heriot-Watt teams will continue to participate in enhancing the public understanding of science by, for example, presenting work at the Royal Society Summer Exhibit and hosting local high-school students in their laboratories. The Oxford investigators have experience producing a series of award-winning video podcasts and the collaboration will build on this experience to produce a joint series of podcasts, aimed a general audience, describing the basic science behind this proposal and the exciting applications which it promises.The grant will support and strengthen an existing and highly successful collaboration between researchers at Princeton, Oxford and Heriot-Watt. The groups have a strong track record performing the experiments and developing the techniques which motivate and enable the research proposed here. Together, the investigators bring together a range of expertise, including magnetic resonance (ESR, ENDOR), quantum information theory, density functional theory, semiconductor physics and organic chemistry. The collaborative nature of this proposed activity allows the focus to be on fundamental physical questions spanning a diverse range of physical quantum spin systems, increasing the impact of the experiments and range of beneficiaries in the scientific community. Finally, the complementary instrumentation across the three institutions provides the necessary set of experimental tools required for this challenging experimental program.