Scalable unitary computing using time-parallelized photonic lattices

Exploiting alternative physical dimensions beyond the spatial domain has been intensively explored to improve the scalability in photonic computing. One approach leverages dynamical systems for time-domain computation, enabling universal and reconfigurable unitary operations. Although this method yields O(N) scaling in both device footprint and gate count, the required computation time increases by O(N 2), which hinders practical implementation due to limitations in quality factors and modulation speeds of optical elements. Here, we propose time-parallelized photonic lattices that achieve O(N) time scalability while preserving the O(N) spatial scaling. We devise a pseudospinor buffer operation that temporally stores the optical information, thereby enabling parallel unitary computation. The proposed method not only mitigates the requirement for high-quality factors but also provides robustness against a broad range of defects, demonstrating the feasibility of time-domain photonic computation.