A method includes configuring a first plurality of beamsplitters in a network of interconnected beamsplitters of an optical circuit into a transmissive state. The optical circuit is configured to perform a linear transformation of N input optical modes, where N is a positive integer. The first plurality of beamsplitters is located along a beam path within the optical circuit and traversing a target location. The method also includes configuring a second plurality of beamsplitters in the network of interconnected beamsplitters of the optical circuit into a reflective state to reconfigure the optical circuit into a reconfigured optical circuit. The reconfigured optical circuit is configured to perform a linear transformation on M input optical modes, where M is a positive integer less than N. The second plurality of beamsplitters is located along at least one edge of the optical circuit.