Joint Detection on Reconfigurable Photonic Processors With Multi-Input Phase Stabilization

We report a joint-detection (JD) experiment between two reconfigurable photonic processors in which Hadamard codewords are generated on a transmitter processor and a Hadamard transform is performed on a receiver (decoder) processor. Crucially, the decoder executes multi-input phase stabilization concurrently with the optical Hadamard combining, ensuring the phase alignment required for coherent joint detection. We demonstrate JD using <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2{\times }2$</tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$4{\times }4$</tex-math></inline-formula> Hadamard transformations and verify stable temporal outputs under active on-chip feedback control (FBC). The approach leverages our multi-input FBC scheme to suppress low-frequency inter-input phase fluctuations and to realize coherent combining consistent with Green-Machine style architectures. These results indicate a practical path to scalable, codeword-level optical joint detection on programmable photonic hardware and are compatible with larger-mode processors and higher-order code families.