Symmetry-driven in-situ physical adjoint computing beyond reciprocity

Abstract

Nonreciprocity enriches wave control and information processing through directional transport, yet challenges conventional in-situ physical adjoint optimization, which relies on reciprocity to acquire adjoint responses. Here we demonstrate symmetry-driven in-situ physical adjoint computing (Sym-iPAC) in nonreciprocal systems, which enables access to adjoint responses on the original hardware through three classes of transpose symmetry: local geometric permutations, complex gauge reweighting, and latent symmetry in effective port dynamics revealed by Schur reduction. Experiments with programmable nonreciprocal microwave networks validate these transpose relations and yield adjoint gradients, enabling closed-loop optimization. These results establish experimentally accessible transpose symmetry as a route to in-situ physical adjoint computing beyond reciprocity.