In-situ Time-domain Physical Adjoint Optimization of Complex Wave Dynamics
Direct optimization of complex wave dynamics through the intrinsic evolution of physical systems is fundamentally limited by the lack of directly accessible gradients. Adjoint methods provide an exact route to gradient computation and have enabled optimization in numerical solvers and, more recently, in frequency-domain physical platforms. Yet their extension to the time domain has remained out of reach, as reproducing time-reversed propagation appears to require non-causal operations or compensating gain. Here we develop a protocol and experimentally demonstrate that time-domain adjoint dynamics can be realized in-situ in linear physical systems without gain, non-causal elements, or auxiliary backward networks. By combining time remapping with a transformation of system variables, we obtain a physically realizable adjoint evolution that constructs gradients from measurable signals. We experimentally demonstrate the approach in a complex RLC network, realizing in-situ optimization for time-dependent objectives, including time-windowed and broadband responses. This framework unifies physical optimization by enabling both system parameters and source excitations to be optimized within the same platform. Our results close the gap between adjoint theory and physical implementation, establishing a general foundation for hardware-native, in-situ temporal optimization across a broad class of complex dynamical systems.