EAGER: Deterministic Placement of Qubits in Cavities for Strongly Coupled Quantum Repeaters

这个关于强耦合量子中继器的量子比特在空腔中的确定性放置的EAGER项目研究了在特殊工程环境（空腔）中最佳放置量子比特的方法，这将允许我们存储，放大和控制量子比特所包含的信息的释放。量子比特对应于量子力学状态，是系统中信息的基本单位，量子力学规则明确地支配着信息的交换、存储和传输。量子系统中的量子位对于更快、更安全地处理和传输复杂信息有着巨大的希望，但存在着深刻的、根本性的挑战，限制了量子位信息的寿命、存储和信号强度。使用特殊设计的空腔可以大大放大量子比特光信号，允许存储量子比特信息，并提供一种控制量子比特信息传输的手段：这种强耦合的量子比特空腔系统可以为更大规模的量子信息系统提供重要的构建块。这里的一个主要挑战在于量子比特在腔内的最佳位置：只要几个原子晶格距离的错位，腔的效率就会急剧下降。这里提出的研究使用半导体平台，开发灵敏的方法来微调腔内原子尺度量子比特的位置，并使用来自量子比特腔系统本身的放大信号来指导这一过程。从这项研究中获得的知识可以对各种量子位腔系统产生深远而广泛的影响，使我们更接近在半导体“芯片”上实现健壮的、可扩展的量子信息系统。技术描述：关于强耦合量子中继器腔中量子比特的确定性放置的拟议EAGER项目将建立在先前涉及4H-SiC纳米桥腔中硅空位的实验中观察到的令人兴奋的结果之上。这些实验表明，确定地将基于缺陷的量子比特放置在与腔的电磁场（模式）最大值的空间重叠的可能性，这是实现量子比特和腔强耦合的最大挑战之一。该项目的工作开发和测试了许多策略，以更好地控制这些基于缺陷的量子位的扩散运动。为了理解和解释放置过程，需要详细了解量子位的能量景观，以及它对热、电子和应变变化的敏感性；因此，实验和理论之间的协作努力是成功的必要条件。因此，本文提出的工作与实验密切相关，并以理论模拟为补充和指导。研究小组评估了扩散过程的热控制，以及更局部和潜在的更好控制的辐射增强扩散过程。该团队还探索了自对准过程的可能性，利用腔本身的高场（模态）区域。实现量子比特与腔内最大场的正确空间重叠可能是实现强耦合的最大挑战。因此，这里提出的研究将对在广泛的光谱范围内创建可扩展的量子信息系统产生重大而广泛的影响。由此产生的强耦合量子位腔器件可以作为有效的量子中继器，在网络中连接来自离散的、空间分离的量子位的信息。此外，该团队所代表的理论与实验之间的协作和紧密耦合的互动提供了一个更丰富、更完整的研究和教育环境，并为如何解决这些具有挑战性的问题设定了基准。

This EAGER project on Deterministic Placement of Qubits in Cavities for Strongly-Coupled Quantum Repeaters studies ways of optimally placing qubits within specially engineered environments (cavities) that will allow us to store, amplify and control the release of information contained by the qubit. Qubits, corresponding to quantum mechanical states, are the fundamental units of information in system where the rules of quantum mechanics explicitly govern the exchange, storage and transmission of information. Qubits within quantum systems hold great promise for faster, more secure processing and transmission of complex information, but there are profound, fundamental challenges that limit the longevity, storage and signal strength of qubit information. The use of specially-designed cavities can result in substantial amplification of qubit optical signals, allow storage of qubit information and provide a means of controlled transmission of the qubit information: such strongly coupled qubit-cavity systems can provide an important building block of larger-scale quantum information systems. A major challenge here lies in the optimal placement of the qubit within the cavity: the efficacy of the cavity can fall off dramatically with misalignments of only several atomic lattice distances. The research proposed here uses a semiconductor platform, developing sensitive means of fine-tuning the placement of atomic-scale qubits within the cavity, and using the amplified signals from the qubit-cavity system itself to guide the process. The knowledge gained from this research can have a profound and wide-ranging impact on a variety of qubit-cavity systems, bringing us much closer to achieving robust, scalable quantum information systems on a semiconductor "chip".Technical Description: The proposed EAGER project on Deterministic Placement of Qubits in Cavities for Strongly-Coupled Quantum Repeaters will build on exciting results observed in prior experiments involving Silicon Vacancies in 4H-SiC nanobridge cavities. These experiments suggest the possibility of deterministically placing defect-based qubits in spatial overlap with the maxima of the electromagnetic fields (modes) of the cavity, one of the greatest challenges in achieving strong coupling of qubit and cavity. The work of this project develops and tests a number of strategies to achieve better control over the diffusive motion of these defect-based qubits. To understand and interpret the placement process, a detailed understanding is required of the energy landscape of the qubit, and its sensitivity to thermal, electronic and strain variations; thus a collaborative effort between experiment and theory is mandatory for success. Therefore, the proposed work closely couples experiments, complemented and guided by theoretical simulations. The research team evaluates thermal control of the diffusion process, as well as the more localized and potentially better-controlled radiation enhanced diffusion processes. The team also explores the possibility of a self-aligned process, using the high field (modal) region of the cavity itself. Achieving the correct spatial overlap of qubit to the maximum field in a cavity is perhaps the greatest challenge to attaining strong coupling. Therefore, the studies proposed here will have a significant, wide-spread impact on creating scalable quantum information systems, across a broad spectral range. The resulting strongly coupled qubit-cavity devices can serve as effective quantum repeaters that link information from discrete, spatially-separated qubits across a network. Moreover, the collaborative and closely-coupled interaction between theory and experiment represented by this team provides a richer and more complete research and education environment, as well as setting benchmarks for how such challenging problems can and should be addressed.