NSF-BSF: Optical Coherent Control of Quantum Dot Spin for Ultra-Fast Quantum Information Processing

在固态量子发射器的许多选择中，砷化铟量子点表现出一些最好的光学特性。它们以近乎完美的效率和纯度发射光子。此外，量子点可以捕获单个电子，这些电子充当与光子强烈相互作用的量子存储器，这是长距离量子网络的关键成分。 但是这些自旋会非常快地失去它们的量子特性，因为它们与大量的核自旋相互作用，而这些核自旋总是存在于宿主衬底的天然晶体结构中。 为了改善这些自旋的量子特性并增加它们持续的时间尺度，需要对半导体中的自旋-核相互作用有更好的基本理解。 这种改进的理解可以直接使方法从大型核自旋池中解耦电子，从而使其相干寿命提高几个数量级。 该计划旨在更好地理解自旋核相互作用，并使用称为动态相干控制的技术提高半导体中的自旋寿命。 这种方法快速操纵自旋，使其在不同的时间尺度上与噪声源解耦。 使用这种技术，主要研究人员将研究半导体基质材料中自旋的噪声特性，并开发新技术来消除它们。 该计划的成功可以实现新一代芯片集成量子设备，可以有效地长距离存储和传输量子信息。 该计划是一个合作的NSF-BSF的建议，结合了马里兰州的量子点光谱学和希伯来大学在耶路撒冷的噪声光谱学和相干自旋控制的专业知识。为了实现计划目标，合作团队将结合联合收割机国家的最先进的噪声光谱学和动态去耦与纳米光子工程。他们将开发一种基于窄带激光超快调制的新型光学激发方案，以实现沿着所有三个轴的完全自旋控制。这种调制可以编程以创建几乎无限的控制序列，从而使自旋控制具有更大的复杂性，并为量子信息处理开辟新的可能性。他们将使用这种新方案来执行量子点自旋量子比特的噪声光谱学，阐明其主要噪声源的物理基础。利用从这些实验中获得的物理洞察力，他们将开发优化的动态解耦序列，可以显着延长量子比特的相干时间，超越当前的最先进水平。将这些光学活性量子存储器耦合到纳米光子腔将提供一条设计高效自旋光子接口的途径，并实现大的可扩展性。 在III-V族半导体中控制和解耦核自旋相互作用的能力将提供具有长寿命相干特性和几乎原始的量子发射的量子位系统。这样的系统可以形成量子网络、光子量子计算机和量子传感器的基本构建块。在III-V族半导体社区中，自旋动力学仍然是一个知之甚少的研究领域，有许多关于主要噪声相互作用和基本相干限制的开放问题。这项研究将揭示这一鲜为人知的物理学，为III-V族半导体材料中的自旋开辟全新的应用和控制工具。 除了研究部分，该计划将包括一个强大的外展工作，以教育高中生和扩大参与STEM领域。这个奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

Among the many choices for solid-state quantum emitters, indium arsenide quantum dots exhibit some of the best optical properties. They emit photons with nearly perfect efficiency and purity. In addition, quantum dots can trap single electrons that act as quantum memories that strongly interact with photons, a key ingredient for long-distance quantum networks. But these spins lose their quantum properties extremely fast because they interact with a large number of nuclear spins that always exist in the natural crystalline structure of the host substrate. In order to improve the quantum properties of these spins and increase the timescales over which they persist requires a better fundamental understanding of spin-nuclear interactions in semiconductors. This improved understanding could directly enable methods to decouple the electrons from the large nuclear spin bath, resulting in orders of magnitude improvements in their coherence lifetime. This program aims to both attain a better understanding of spin nuclear interactions and improve spin lifetimes in semiconductors using a technique called dynamical coherent control. This approach manipulates the spin rapidly to decouple it from noise sources on different timescales. Using this technique, the principal investigator will study the noise properties of spins in a semiconductor host material, and develop new techniques to eliminate them. Success of this program could enable a new generation of chip-integrated quantum devices that can efficiently store and transmit quantum information over long distances. This program is a collaborative NSF-BSF proposal which combines the expertise of the University of Maryland in quantum dot spectroscopy and the Hebrew University in Jerusalem on noise spectroscopy and coherent spin control.To achieve the program goals, the collaborative team will combine state-of-the-art noise spectroscopy and dynamical decoupling with nanophotonic engineering. They will develop a novel optical excitation scheme based on ultra-fast modulation of a narrowband laser to achieve complete spin control along all three axes. Such modulation can be programmed to create nearly unlimited control sequences, thus enabling spin control with significantly greater complexity and opening new possibilities for quantum information processing. They will use this new scheme to perform noise spectroscopy of the quantum dot spin qubit, elucidating the physics underlying its dominant noise sources. Using the physical insight gained from these experiments, they will develop optimized dynamical decoupling sequences that could significantly extend the coherence time of the qubit beyond current state-of-the-art. Coupling these optically active quantum memories to nanophotonic cavities will provide a path to engineer efficient spin-photon interfaces, and achieve large scalability. The ability to control and decouple nuclear spin interactions in III-V semiconductors would provide a qubit system with long-lived coherence properties and nearly pristine quantum emission. Such a system could form the fundamental building block for quantum networks, photonic quantum computers, and quantum sensors. In the III-V semiconductor community, spin dynamics remains a poorly understood area of research with many open questions regarding the dominant noise interactions and fundamental coherence limits. This research will shed light on this poorly understood physics, opening up brand new applications and control tools for spin in III-V semiconductor materials. In addition to the research component, this program will include a strong outreach effort to educate high school students and broaden participation in STEM fields.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.