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

该奖项的全部或部分资金来自《2021年美国救援计划法案》(公法117-2)。根据量子力学原理运行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，计算系统必须针对硬件中不可避免的故障保持健壮。有必要以容错的方式纠正由于硬件故障而引入系统中的错误，以便即使计算机的一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在量子纠错方面展示了具有里程碑意义的实验。然而，它们距离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还很遥远。NSF职业生涯计划的目标是统一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，为使用新出现的量子硬件实现实用、可扩展的容错量子计算开辟道路。为了扩大该计划的更广泛影响，将开发动手操作的量子信息科学课程，让学生参与活跃的量子信息研究，并吸引从物理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，该计划将为当地社区和年轻人建立一个脚手架教育倡议。该程序采用自下而上的方法来完成资源高效的容错量子纠错这一雄心勃勃的任务。这种方法将特别适用于新兴的超导连续变量(CV)或玻色量子硬件，其基础是在超导振荡器的量子态中存储比特的量子信息或量子比特。玻色编码背后的动机是，原则上，通过设计或直接应用于振荡器模式的主动纠错，可以使它们对某些噪声源具有弹性。不幸的是，实际的实验噪声更加复杂，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，在考虑到现实的实验噪声的情况下，对CV量子比特进行稳健的量子控制。噪声中的已知结构将被用来设计高效的容错协议，而不是仅仅依赖于降低CV量子硬件的噪声。这一方向是基于这样一种观察，即在一个给定的系统中，并不是所有的错误都是同样有害的。一些错误更具传染性，并且在电路中迅速传播，而且还有一些类型的错误更容易使用特定的纠错码来检测。因此，如果量子比特的噪声通道能够被定制以抑制传染性错误，那么纠错就可以变得更加有效，甚至可能以略微增加仍然更容易检测到的错误为代价。这种非对称噪声量子比特可以通过在超导振荡器中使用CV编码的多种方式来实现。因此，自下而上的方法将被用来开发具有平面拓扑纠错码的可扩展容错结构，该结构可以利用非对称噪声CV量子比特的噪声特性。这项工作不仅将导致高效的CV容错纠错，还将为下一代量子硬件的设计提供信息，使之能够进行实用的、可扩展的量子计算。该奖项反映了NSF的法定使命，并已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。

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.