Collaborative Research: EAGER: Quantum Manufacturing: Vertical Coupling and Cross-Talk Shielding of Superconducting Quantum Devices

下一代超导量子器件的发展所面临的主要挑战之一是大量单个超导量子比特（qubit）的高密度三维（3D）集成。虽然超导量子器件作为一种技术已经达到了高度成熟的水平，但将量子位彼此耦合以实现用于实际计算的大规模电路仍然是一个挑战。该项目旨在通过探索一种新的方法来解决这一挑战，该方法使用插入量子位层之间的薄电磁耦合器来耦合超导电路。拟议的工作将基于量子元素的创新整合，这些元素本身在PI和Co-PI的实验室中已经建立。拟议工作的成功执行将扩大我们对超导器件中量子态的了解，并将导致改进的量子制造方法的发展，这些方法对实际的量子信息处理技术具有广泛的兴趣。该团队致力于指导研究生和本科生，并扩大量子工程中代表性不足的群体的参与。此外，PI将参与旨在提高学生对物理，材料科学和数学的认识的外展工作。这项工作的很大一部分将接触当地美洲土著社区的学生。开发超导量子位的3D集成的新方法对于实现适合运行实际相关算法的高深度电路至关重要。用于transmon量子位的电流耦合技术通常涉及相对较大（毫米大小）的共面谐振器，而对于相位量子位，正在研究各种不同的电容或电感耦合方法。尚未确定纵向扩展的最佳解决办法。现有的方法通常是平面的，部分原因是源于用于创建量子位约瑟夫森结（JJ）的技术的限制，该技术通常是角度沉积和隧道势垒的受控氧化。这导致JJ电路的低空间密度和相干限制串扰。为了应对这一挑战，PI将制造高质量的JJ阵列芯片，并通过在微波频率下工作的波导阵列垂直连接它们。虽然每个使能组件和制造方法都已得到演示，但它们的集成是一项艰巨的任务，具有高风险，而共同PI在应对这一挑战方面具有独特的优势。智力意义：该团队对JJ和串扰屏蔽的全3D集成的愿景处于早期阶段，尚未经过实验测试，但提出了一种潜在的变革性方法，可以在一次中风中解决有效超导电路耦合，高密度3D垂直集成和串扰缓解的三重挑战。 此外，该项目将培养研究生在最先进的量子器件纳米纤维，先进的材料生长和量子传输。PI还将开发针对本科生的量子信息科学课程和针对研究生的量子工程/制造课程。该奖项反映了NSF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。

One of the main challenges facing the development of next-generation superconducting quantum devices is high-density three-dimensional (3D) integration of large numbers of individual superconducting quantum bits (qubits). While superconducting quantum devices have reached a high level of maturity as a technology, coupling of qubits to one another to enable large-scale circuits for practical computation still remains a challenge. This project seeks to address this challenge by exploring a new approach for coupling superconducting circuits using a thin electromagnetic coupler interposed between qubit layers. The proposed work will be based on an innovative integration of quantum elements that are by themselves well-established in the PI’s and Co-PIs’ labs. Successful performance of the proposed work will expand our knowledge of quantum states in superconducting devices and will result in the development of improved quantum manufacturing approaches of broad interest for practical quantum information processing technologies. The team is committed to mentoring graduate and undergraduate students and to broadening the participation of under-represented groups in quantum engineering. In addition, the PIs will be involved in outreach efforts aiming to raise awareness about physics, materials science, and mathematics to school students. A substantial part of this effort will reach out to school students from the local Native American community. Developing new approaches to 3D integration of superconducting qubits is of crucial relevance for realizing high-depth circuits suitable for running practically relevant algorithms. Current coupling techniques for transmon qubits typically involve relatively large (millimeter-sized) coplanar resonators, while for phase qubits a variety of different capacitive or inductive coupling approaches are being investigated. No optimal solution has yet been identified for vertical expansion. Existing approaches are typically planar, due in part to limitations stemming from the technology used to create the qubit Josephson junctions (JJs) typically angle-deposition and controlled oxidation of the tunnel barrier. This results in low spatial densities for JJ circuits and coherence-limiting cross-talk. In order to address this challenge, the PIs will fabricate high-quality JJ array chips and link them vertically via waveguide arrays operating in the microwave frequencies. While each enabling component and manufacturing method has been demonstrated, their integration is a daunting task with high-risk and the co-PIs are uniquely positioned to tackle this challenge. Intellectual significance: the team’s vision of full-3D integration of JJs and cross-talk shielding is in its early stages and untested experimentally, yet presents a potentially transformative approach to solve, in a single stroke, the triple challenge of efficient superconducting circuit coupling, high-density 3D vertical integration, and cross-talk mitigation. Additionally, the project will train graduate students in state-of-the art quantum device nanofabrication, advanced materials growth, and quantum transport. The PIs will also develop courses on quantum information sciences aimed at undergraduates and quantum engineering/manufacturing aimed at graduate students.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.