Methods and apparatus for mitigating imperfections in optical circuits

An apparatus, comprising:

• N input ports, N being a positive integer;
• and
• a network of interconnected beamsplitters in optical communication with the N input ports, the network of interconnected beamsplitters including:
• a first plurality of beamsplitters located along a beam path traversing a target location and configured into a transmissive state, the target location identifying an imperfection in the network of interconnected beamsplitters;
• a second plurality of beamsplitters located along at least one edge of the network of interconnected beamsplitters and configured into a reflective state, the first plurality of beamsplitters and the second plurality of beamsplitters defining a region of the network of interconnected beamsplitters, the region including the target location, and the first plurality of beamsplitters and the second plurality of beamsplitters circumventing the imperfection;
• and
• a third plurality of beamsplitters that are reconfigurable and configured to perform a linear transformation on M input optical modes independent of the region, M being a positive integer less than N.

An apparatus, comprising:

• a plurality of input ports;
• and
• a plurality of interconnected beamsplitters in optical communication with the plurality of input ports, the plurality of interconnected beamsplitters including:
• a first plurality of beamsplitters located along a beam path traversing a target location and configured into a transmissive state, the target location identifying an imperfection in the plurality of interconnected beamsplitters;
• a second plurality of beamsplitters located along at least one edge of the plurality of interconnected beamsplitters and configured into a reflective state, the first plurality of beamsplitters and the second plurality of beamsplitters defining a region of the plurality of interconnected beamsplitters, the region including the target location, and the first plurality of beamsplitters and the second plurality of beamsplitters circumventing the imperfection;
• and
• a third plurality of beamsplitters configured to perform a linear transformation on a plurality of input optical modes independent of the region.