Scalable control stack architecture for fault-tolerant quantum computing

A scalable control stack is the backbone of a programmable, fault-tolerant quantum computer. Operating large amounts of qubits requires latency and throughput-optimized feedback for calibration, quantum error correction, and hybrid computing. As quantum processing units (QPUs) grow toward thousands of qubits, the control stack faces scalability challenges in synchronized I/O, feedback connectivity, and throughput. Here, we present a feedback architecture and capabilities that address these challenges. The advanced feedback architecture across control modules and mainframes, enabling low-latency, high-throughput feedback for large qubit arrays, to flexibly share measurement results between,control and readout pulse processors and decoding modules in real time. We showcase the feedback capabilities on a QPU using several Qubit Readout and Control modules, a microwave module that offers a high channel density. By supporting qubit-agnostic feedback across modular hardware, our architecture opens the path to scalable implementations of qubit calibrations, circuit branching and error-corrected qubit networks.