Accurate Self-Configuration of Rectangular Multiport Interferometers

Multiport interferometers based on integrated beamsplitter meshes are widely used in photonic technologies. While the rectangular mesh is favored for its compactness and uniformity, geometry resists conventional self-configuration approaches, which essential to programming large presence of fabrication error. Here, we present a configuration algorithm, related $2\ifmmode\times\else\texttimes\fi{}2$ block decomposition unitary matrix, that overcomes this limitation. Our proposed algorithm robust errors, requires no prior knowledge process variations, relies only external sources detectors. We show using technique reduces effect errors by same quadratic factor observed triangular meshes. This relaxes significant limit size multiport interferometers, removing major roadblock scaling optical quantum machine-learning hardware.