High-Fidelity Ternary Quantum Logic for Near-Term Algorithms

量子信息科学(QIS)正在进入噪声中尺度(NISQ)时代，在这个时代，执行超出经典计算能力的算法变得现实。已经为NISQ时代的量子计算机提出了影响多个领域的应用，从药物设计到资源分配优化。对这项工作至关重要的是探索决定QIS实现的特征和动力学的基本物理，以及如何利用这种理解来改进量子控制。该项目致力于通过利用超导电路的自然丰富结构来开发三值量子逻辑处理器，从而扩展现代处理器的资源效率。随着QIS经历这样的增长，招聘和培训一支敬业和多样化的科学家队伍至关重要。该项目的研究将由研究生在高级人员的指导下进行，以获得未来学术和工业研究职业所需的技能。发展这一领域并不局限于已经涉足学术界的研究生。在暑期实习计划中，来自东湾区当地高中的学生将被介绍到QIS研究中涉及的主题和技能，以及参与实践体验。这里的核心挑战是开发高保真双量子门，这是产生纠缠和普遍量子计算的关键成分。为了实现这一点，处理器利用可调耦合方案来生成快速门的强交互，同时允许抑制不想要的交互。为了验证这些门技术，开发并采用了可扩展的Qutrit处理器基准测试，测量了与多Qutrit处理器兼容的最先进的保真度。最后，该处理器用于执行量子-经典混合算法，如适用于三值量子逻辑的量子近似优化算法(QAOA)。NISQ时代的算法，特别是利用三值逻辑，展示了这样一个处理器的能力，同时适应和开发必要的误差缓解技术，在存在噪声的情况下，对准确性至关重要。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。

Quantum information science (QIS) is entering the noisy intermediate-scale (NISQ) era, where executing algorithms that reach beyond classical computational capability becomes realistic. Applications impacting several fields, ranging from pharmaceutical design to resource allocation optimization, have been proposed for NISQ-era quantum computers. Vital towards this effort is an exploration of the fundamental physics determining the characteristics and dynamics of QIS implementations, and how this understanding can be utilized for improved quantum control. This project focuses on extending the resource efficiency of modern processors, by leveraging the naturally rich structure of superconducting circuits to develop a ternary quantum logic processor. With QIS experiencing such growth, it is essential to recruit and train an engaged and diverse workforce of scientists. Research for this project will be conducted by graduate students, with mentorship from senior personnel, gaining the skills required for future careers in academic and industrial research. Developing the field is not limited to graduate students already involved in academia. In a summer internship program, students from local East Bay Area high schools will be introduced to the topics and skills involved in QIS research, as well as engaging in hands-on experience.The central challenge here is development of high-fidelity two-qutrit (quantum trit) gates, an essential ingredient for generating entanglement and universal quantum computation. To accomplish this, the processor utilizes a tunable coupling scheme to generate strong interaction for fast gates, while allowing for suppression of unwanted interactions. To verify these gate techniques, scalable qutrit processor benchmarking is developed and employed, measuring state-of-the-art fidelities compatible with a multi-qutrit processor. Finally, the processor is used to execute hybrid quantum-classical algorithms, such as the quantum approximate optimization algorithm (QAOA), well suited to ternary quantum logic. NISQ-era algorithms specifically utilizing ternary logic demonstrate the power of such a processor, while adapting and developing necessary error mitigation techniques vital to accuracy in the presence of noise.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.