  A crucial challenge to the scaling up of linear optical interferometers is
the presence of defective optical components resulting from inevitable
imperfections in fabrication and packaging. This work presents a method for
circumventing such defective components including lossy modes and unresponsive
phase shifters and beam-splitters. The method allows for using universal linear
optical interferometers with such defects as smaller universal interferometers.
The method presented here tolerates remarkably high defect rates in
constructing linear optical interferometers, thus bringing closer to reality
the possibility of obtaining quantum advantage with linear optics.
