CAREER: Noise-Tailored Architectures for Fault-Tolerant Continuous-Variable Quantum Computing

该奖项全部或部分由《2021年美国救援计划法案》（公法117-2）资助。基于量子力学原理的计算硬件开启了强大技术的可能性，这些技术可以完成基于经典布尔代数的处理器无法完成的任务。然而，为了充分利用量子现象的力量，必须使计算系统能够抵御硬件中不可避免的故障。有必要以容错的方式纠正由于硬件故障而引入系统的错误，以便即使计算机的某些组成量子组件发生故障，计算机也能继续可靠地运行。最先进的量子技术已经导致了量子纠错的里程碑式实验的演示。然而，它们仍远未达到量子计算实际应用所需的大规模容错的严格性能和资源要求。这个NSF CAREER项目的目标是应用我们在开放量子系统理论和控制以及容错纠错理论方面的专业知识，用新兴的量子硬件为实用的、可扩展的容错量子计算制定一条路线。为了扩大该计划的广泛影响，将开发动手量子信息科学课程，让学生参与积极的量子信息研究，并吸引从物理学到电气和计算机工程等领域的人才。此外，为了维持未来多样化的量子劳动力，该项目将为当地社区和青年建立一个框架式的教育倡议。该计划采用自下而上的方法来完成资源高效容错量子纠错的宏伟任务。该方法将被开发，特别是用于新兴的超导连续变量（CV）或玻色子量子硬件，该硬件基于在超导振荡器的量子态中存储比特量子信息或量子位。玻色子编码背后的动机是，原则上，它们可以通过设计或直接应用于振荡器模式的主动误差校正来抵抗某些噪声源。不幸的是，实际实验噪声更为复杂，到目前为止，在实验室中实现的噪声抑制量相当有限。在这个项目中，PI将开发新的策略，在考虑到实际实验噪声的情况下，对CV量子比特进行鲁棒量子控制。而不是仅仅依赖于使CV量子硬件减少噪声，噪声中的已知结构将用于设计有效的容错协议。这个方向是基于这样的观察：在给定的系统中，并非所有的错误都是同样有害的。有些错误更具传染性，在电路中传播迅速，还有一些类型的错误使用特定的纠错代码更容易检测到。因此，如果量子位的噪声通道可以被调整以抑制传染性错误，甚至可能以稍微增加更容易检测到的错误为代价，错误纠正可以更有效。这种非对称噪声量子比特可以在超导振荡器中使用CV编码以多种方式实现。因此，将采用自底向上的方法开发具有平面拓扑纠错码的可扩展容错架构，该架构可以利用非对称噪声CV量子位的噪声特性。这项工作不仅将导致高效的cv容错纠错，而且还将为下一代量子硬件的设计提供信息，从而实现实用的、可扩展的量子计算。该奖项反映了美国国家科学基金会的法定使命，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。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). A computing hardware operating on principles of quantum mechanics opens up the possibility of powerful technologies that can accomplish tasks beyond what is possible with processors based on classical Boolean algebra. However, to fully harness the power of quantum phenomena the computing system must be made robust against inevitable faults in the hardware. It becomes necessary to correct errors introduced in the system due to faulty-hardware in a fault-tolerant manner so that the computer continues to function reliably even if some of its constituent quantum components have failed. State-of-the-art quantum technologies have led to demonstration of landmark experiments in quantum error correction. However, they are still far away from reaching the stringent performance and resource requirements for fault-tolerance at a large scale needed for practical applications of quantum computing. The goal of this NSF CAREER program is to apply our expertise in the theory and control of open quantum systems and theory of fault-tolerant error correction in unison to chart a course for practical, scalable fault-tolerant quantum computation with new emerging quantum hardware. To extend the broader impacts of this program, hands-on quantum information science curricula will be developed to engage students in active quantum information research and to draw talent from fields ranging from physics to electrical and computer engineering. Moreover, to sustain a diverse future quantum workforce, the program will establish a scaffolded education initiative for the local community and youth. This program takes a bottoms-up approach to accomplish the ambitious task of resource-efficient fault-tolerant quantum error correction. The approach will be developed, in particular, for the emerging superconducting continuous-variable (CV) or bosonic quantum hardware based on storing a bit of quantum information or qubit in quantum states of a superconducting oscillator. The motivation behind bosonic encodings is that, in principle, they can be made resilient against some sources of noise either by design or by active error correction applied directly to the oscillator mode. Unfortunately, practical experimental noise is more complex and the amount of noise suppression achieved so far in the laboratory is quite limited. In this program the PI will develop new strategies for robust quantum control of CV qubits taking into account realistic experimental noise. Rather than solely relying on making the CV quantum hardware less noisy, known structures in the noise will be used to design efficient fault-tolerant protocols. This direction is based on the observation that not all errors are equally harmful in a given system. Some errors are more contagious and spread rapidly in a circuit and then there are also some types of errors that are easier to detect using a particular error-correcting code. Thus, error-correction can be made more effective if the noise channel of a qubit could be tailored to suppress contagious errors, perhaps even at the cost of slightly increasing errors that are nonetheless easier to detect. Such asymmetric-noise qubits can be realized in a number of ways using CV encoding in superconducting oscillators. Thus, the bottoms-up approach will be taken to develop scalable fault-tolerant architectures with planar topological error correcting codes that can leverage the noise properties of asymmetric-noise CV qubits. This work will not only lead to efficient CV-fault-tolerant error correction, but will also inform the design of next-generation quantum hardware, enabling practical, scalable quantum computing.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.