Quantum computing with photonic GKP qubits

Numerous architectures have been proposed for fault-tolerant quantum computing. Photonics offers a promising platform for operating quantum computers at scale, owing to the mass-manufacturability of photonic chips that can be integrated into modules, fiber optics to network those modules, and room temperature operation of the majority of the requisite components. In this talk, we present a comprehensive and optimized architecture for fault-tolerant-scale quantum computing using photonic Gottesman-Kitaev-Preskill (GKP) qubits, complete with a detailed analysis of its tolerances for optical loss, which is the dominant and most challenging hurdle to crossing the fault-tolerant threshold. We determine thresholds for loss in all optical paths and components of the machine, and assess trade-offs between depth of multiplexing circuits and loss tolerance. This architecture lays out a path, performance targets, and next steps to cross the fault-tolerant threshold and scale photonic quantum computers to the point of addressing useful applications.