QII-TAQS: Quantum Photonics at Telecommunications Wavelengths Based on Metal-Ion-Doped Materials

快速发展的量子信息科学领域利用量子态的独特特性，以传统信息、通信和计算机技术无法实现的新方式处理、存储和传输数据。为了使这些下一代量子系统在实际应用中实现，迫切需要开发芯片级集成组件，以执行传统信息系统所需的所有功能，但在量子水平上的要求要高得多。虽然已经演示了许多这样的单独组件，但当前的实现采用了各种不同的、通常不兼容的方法，这些方法不容易相互集成或与现有的传统技术基础设施（如光纤网络和经典计算机处理器）集成。为了解决这种整合的需要，该项目汇集了加州理工学院量子光子学和量子硬件制造、加州理工学院量子理论和半导体物理、德克萨斯大学奥斯汀分校半导体生长和器件以及蒙大拿州立大学量子退相干、固态化学和光物质相互作用方面的专业研究人员。这个跨学科团队试图通过将稀土离子（最成功的量子系统之一）与半导体材料结合起来，开发和设计集成量子硬件，这些材料可以很容易地与现有的光学和电子技术集成。除了对量子信息科学的直接影响外，这项研究还为离子的纳米级特性和半导体中的缺陷提供了新的见解，因为量子态的内在脆弱性可以用作材料相互作用和缺陷的独特强大探针。反过来，这些信息可以用来加速离子半导体技术的发展，远远超出量子应用，如电致发光器件，集成电光元件，高速光子信号处理和传感系统。稀土离子掺杂到复合氧化物中，使光量子存储器的最新技术得以展示，并在实现微波到光量子转导和单量子比特方面显示出良好的前景。特别是，Er3+提供1.5微米电信波长的直接光学寻址，允许与现有基础设施和商业硬件集成。为了实现基于金属离子掺杂材料的强大的、可扩展的量子光子器件，该技术将理想地基于现有的半导体材料，这些材料很容易用传统工艺制造，而不是现有的氧化物材料，这些材料很难整合到集成量子器件中。本研究探索了在III-V半导体中掺杂具有电信波长跃迁的稀土和过渡金属离子的量子光学性质，并利用这些开发的材料构建了可扩展的纳米光子量子器件平台。这些材料有望将金属离子中心的优异量子相干性与通过分子束外延生长高质量层状材料的技术能力相结合，并制造高性能集成半导体器件。具体来说，这项工作研究了半导体中尚未研究的低金属离子浓度体系，特别是量子信息科学中使用的低温，其中许多可能导致弛豫的传统机制被强烈抑制。此外，像Er3+这样的离子的光学和自旋量子相干性在半导体中仍然完全未被探索，以及这些宿主材料特有的材料物理效应（电荷注入、俄歇弛豫、强晶格极化等）。该项目解决了可扩展量子光子系统的关键需求，通过密切协调材料特性和化学，纳米级动力学和退相干现象的研究和建模，以及量子器件工程，以及在这些材料以前未探索的制度中发现和基础研究新的退相干和相互作用现象。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The rapidly developing field of quantum information science exploits the unique properties of quantum states to process, store, and transmit data in new ways that are impossible to achieve with conventional information, communication, and computer technologies. For these next-generation quantum systems to be implemented in practical, real-world applications, there is a critical need to develop chip-scale integrated components that perform all the functions required for traditional information systems, but at the tremendously more demanding quantum level. While many such individual components have been demonstrated, current implementations have employed a wide variety of disparate, and often incompatible, approaches that are not easily integrated with each other or with the existing conventional technological infrastructure, such as optical fiber networks and classical computer processors. To address the need for such integration, this project brings together researchers with expertise in quantum photonics and quantum hardware fabrication at Caltech, quantum theory and semiconductor physics at Caltech, semiconductor growth and devices at University of Texas - Austin, and quantum decoherence, solid-state chemistry, and light-matter interactions at Montana State University. This interdisciplinary team seeks to develop and design integrated quantum hardware by incorporating rare-earth ions, which are one of the most successful quantum systems, with semiconductor materials that can be easily integrated with existing optical and electronic technologies. In addition to the direct impact in quantum information science, this research also provides new insights into the nanoscale properties of ions and defects in semiconductors, since the intrinsically fragile nature of quantum states can be used as a uniquely powerful probe of interactions and imperfections in materials. In turn, this information can be used to accelerate the development of ion-enabled semiconductor technologies far beyond quantum applications, such as electroluminescent devices, integrated electro-optic components, and high-speed photonic signal processing and sensing systems. Rare-earth-ions doped into complex oxides have enabled demonstrations of state-of-the-art technologies for optical quantum memories and shown excellent prospects for implementing microwave to optical quantum transduction and single quantum bits. In particular, Er3+ provides direct optical addressing at 1.5 micron telecommunications wavelengths that allows integration with existing infrastructure and commercial hardware. To enable robust, scalable quantum photonic devices based on metal-ion-doped materials, the technology would be based ideally on established semiconductor materials that are easily fabricated with conventional processes rather than the existing oxide materials that are difficult to incorporate into integrated quantum devices. This research explores the quantum optical properties of rare-earth and transition-metal ions with transitions at telecom wavelengths doped into III-V semiconductors and uses these developed materials to build a scalable nanophotonic quantum device platform. These materials show promise for combining the excellent quantum coherence properties of the metal-ion centers with the technological capabilities for growing high quality layered materials via molecular beam epitaxy and fabricating high-performance, integrated semiconductor devices. Specifically, this work investigates the low metal-ion concentration regime that has not yet been studied for semiconductors, particularly for the cryogenic temperatures employed in quantum information science where many of the traditional mechanisms that can cause relaxation are strongly suppressed. Furthermore, the optical and spin quantum coherence properties of ions such as Er3+ remain entirely unexplored in semiconductors, along with effects of materials physics unique to these host materials (charge injection, Auger relaxation, strong lattice polarization, etc.). The project addresses the critical need for scalable quantum photonic systems by closely coordinating studies and modeling of material properties and chemistry, nanoscale dynamics and decoherence phenomena, and quantum device engineering along with the discovery and fundamental study of new decoherence and interaction phenomena in this previously unexplored regime for these materials.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.