Quantum spintronics using donors in isotopically engineered silicon

对材料制造和自旋控制技术的精细控制已经达到成熟，自旋电子学可以超越纯粹的经典效应，开始充分利用叠加和纠缠的独特量子性质。量子自旋电子学的潜在应用范围包括量子信息处理器，包括通过巡回电子自旋传输量子信息，自旋系综中的单微波光子存储，以及利用纠缠从根本上提高精度的新一代传感器。量子自旋电子学的关键组成部分包括保持自旋相干性和产生高纯度的纠缠。通过这个合作研究项目，我们建议利用同位素工程硅中施主的电子和核自旋来解决这两个挑战。我们的初步实验表明，这种材料具有最大的高纯度纠缠和长相干时间的潜力，它们与传统电子学的潜在集成是进一步的优势。通过我们的初步合作，我们已经在X波段(0.3T)和6K证明了与硅中的P施主相关的电子和核自旋之间的假纠缠。我们已经利用我们在这些实验中获得的保真度来计算通过这种技术产生纯纠缠的阈值：例如，移动到更高的磁场(&gt；3.5T)和更低的温度(&lt；4K)。我们拥有满足这些要求的主要仪器，并将作为该项目的一部分，演示在硅中可控地产生纯自旋纠缠。然后，我们将开发保存纠缠的方法，并了解自旋输运的影响。将硅同位素纯化到28Si，可以显著提高施主电子的自旋相干性，达到几十毫秒。然而，核自旋是一种强大的资源，在其中可以暂时存储和恢复相干电子自旋态。我们已经用这种方式演示了核自旋作为量子存储器的用途，产生了高达几秒的相干时间。我们将了解自旋退相干的机制，并使用材料改进和动态解耦和纠错等活跃技术，推动固体中最长自旋相干时间的极限。我们将要研究的自旋系综能够以分布式状态存储多比特信息，类似于全息信息存储。我们将在最初工作的基础上，在一个系综中存储和检索100个相干弱微波激发，以建立多模量子存储器，在低外加磁场下工作，II)下到单光子能级III)能够存储几秒钟的相干量子态。通过这个项目，我们将执行仪器和材料的迭代开发：由同位素工程材料实现的更长的相干时间将把我们的仪器推向极限，通过改进仪器，我们可以提取和了解材料的内在性质，以便进一步增强。在项目结束时，我们将在同位素工程硅中建立施主自旋，作为量子自旋电子学的先驱材料，并展示量子自旋电子器件的基本组件。

The exquisite control over materials fabrication and spin control techniques has reached a maturity where spintronics can go beyond purely classical effects and begin to fully exploit the unique quantum properties of superposition and entanglement. Potential applications arising from quantum spintronics range from quantum information processors, including the transmission of quantum information via itinerant electron spins, single microwave photon storage within spin ensembles, and new generation of sensors exploiting entanglement to yield fundamentally enhanced precision. Key ingredients for quantum spintronics include the preservation of spin coherence and the generation of high-purity entanglement. Through this collaborative research project, we propose to address both of these challenges using both the electron and nuclear spin of donors in isotopically engineered silicon. Our preliminary experiments show that such materials offer the greatest potential for high-purity entanglement and long coherence times, and their potential integration within conventional electronics is a further advantage.Through our initial collaboration, we have already demonstrated 'psuedo-entanglement' between the electron and nuclear spin associated with a P-donor in silicon at X-band (0.3 T) and 6K. We have used the fidelities which we achieved in those experiments to calculate thresholds for generating pure entanglement by this technique: for example moving to higher magnetic fields (>3.5T) and lower temperatures (<4K). We possess the major instrumentation to meet these requirements, and will demonstrate the controlled generation of pure spin entanglement within silicon as part of this project. We will then develop methods for preserving entanglement and understand the effect of spin transport.The isotopic purification of silicon to 28Si yields dramatic improvements in the donor electron spin coherence to tens of milliseconds. However, the nuclear spin is a powerful resource into which the coherent electron spin state may be temporarily stored and retrieved. We have demonstrated the use of the nuclear spin as a quantum memory in this way, yielding coherence times up to several seconds. We will understand the mechanisms for spin decoherence and, using materials refinement and active techniques such as dynamic decoupling and error-correction, we will push the limits of the longest spin coherences times in the solid state. The spin ensembles which we will be studying are capable of storing multiple bits of information in distributed states, analogous to holographic information storage. We shall build on our initial work, in which we stored and retrieved 100 coherent weak microwave excitations within an ensemble, to establish multimode quantum memories working i) at low applied magnetic fields ii) down to the single photon level iii) capable of storing coherent quantum states for several seconds.Throughout this project we will be performing an iterative development of instrumentation and materials: longer coherence times enabled by the isotopically engineered materials will push us to the limits of our instrumentation, and by improving the instrumentation we can then extract and understand intrinsic properties of the materials so that they may be further enhanced.At the end of the project we shall have established donor spins in isotopically engineered silicon as the forerunner material for quantum spintronics and demonstrated the essential components for a quantum spintronics device.