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

在固态量子发射体的众多选择中，砷化铟量子点表现出一些最好的光学性能。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，光子是长距离量子网络的关键组成部分。但这些自旋极快地失去了它们的量子性质，因为它们与大量的核自旋相互作用，这些自旋总是存在于宿主衬底的自然晶体结构中。为了改善这些自旋的量子性质，并增加它们持续存在的时间尺度，需要更好地从根本上理解半导体中的自旋-核相互作用。这种更好的理解可以直接使方法将电子从大的核自旋池中分离出来，从而使它们的相干寿命提高数量级。该计划旨在通过一种称为动态相干控制的技术，既更好地了解自旋核相互作用，又提高半导体的自旋寿命。这种方法快速操纵自旋，将其与不同时间尺度上的噪声源分离。使用这项技术，首席研究员将研究半导体主体材料中自旋的噪声特性，并开发新的技术来消除它们。这一计划的成功可能使新一代芯片集成量子设备能够高效地存储和远距离传输量子信息。该计划是一项NSF-BSF合作计划，它结合了马里兰大学和耶路撒冷希伯来大学在噪声光谱和相干自旋控制方面的专业知识。为了实现计划目标，合作团队将把最先进的噪声光谱和动态去耦合与纳米光子工程结合起来。他们将开发一种新的基于窄带激光超快调制的光学激发方案，以实现沿所有三个轴的完全自旋控制。这种调制可以被编程为创建几乎无限的控制序列，从而使自旋控制变得更加复杂，并为量子信息处理打开了新的可能性。他们将使用这一新方案对量子点自旋量子比特进行噪声光谱，阐明其主要噪声源背后的物理基础。利用从这些实验中获得的物理洞察力，他们将开发出优化的动态去耦合序列，这可能会显著延长量子比特的相干时间，超出目前的最先进水平。将这些光学活性量子存储器耦合到纳米光子腔将为设计高效的自旋-光子接口提供一条途径，并实现大规模可伸缩性。控制和解耦III-V半导体中的核自旋相互作用的能力将提供一个具有长寿命相干特性和近乎原始的量子发射的量子比特系统。这样的系统可以构成量子网络、光子量子计算机和量子传感器的基本构件。在III-V半导体领域，自旋动力学仍然是一个鲜为人知的研究领域，有许多关于主要噪声相互作用和基本相干限制的悬而未决的问题。这项研究将揭示这一鲜为人知的物理学，为自旋在III-V半导体材料中开辟全新的应用和控制工具。除了研究部分，该计划还将包括一个强有力的外展努力，以教育高中生并扩大对STEM领域的参与。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.