CSR: Scalable Modular Fault-Tolerant Quantum Hardware through Pauli Based Computing

Quantum computers may one day solve important problems that are far too difficult for ordinary computers, but useful machines will need millions of tiny parts called quantum bits. A single device is unlikely to hold all of them. Instead of building one enormous machine, this project treats the future computer as a team of connected modules, each executing part of the job. It studies how many smaller quantum devices can work together as one reliable computer. It focuses on how these devices share quantum links, how the computer decides which actions to take next, and how it protects fragile information from mistakes. The goal is to make large quantum computers more practical by designing the rules and software needed for connected modules to cooperate. The project frames modular fault-tolerant quantum computing around Pauli-Based Computation, where quantum algorithms are carried out through adaptive Pauli product measurements, classical feed-forward, and magic states. Thrust A develops the entanglement supply chain, including Bell pair generation, purification, buffering, Greenberger-Horne-Zeilinger state preparation, and code adapters for measurements across modules. Thrust B develops compilation methods that convert algorithms into measurement graphs, schedules, and entanglement demand profiles while optimizing logical error rate, latency, and network resource use. Thrust C develops dynamic code resizing, so code distance can grow or shrink during execution as reliability needs change. Resulting tools include a code-adapter library, compiler prototype, grow and shrink protocols, and benchmark suites. Broader impacts include stronger foundations for future quantum technologies, public software, and workforce training. The project will produce design targets for hardware teams, such as needed entanglement quality, generation rates, memory lifetimes, and timing constraints. These targets can help guide machines aimed at chemistry, materials, optimization, and other demanding applications. The compiler prototype, hardware parameter database, simulation tools, and benchmark suite will be released as open-source resources with documentation. Course modules and self-study materials will be added to annual summer schools in numerical quantum information science, supporting graduate students and instructors. 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.