  Recent developments in integrated photonics technology are opening the way to
the fabrication of complex linear optical interferometers. The application of
this platform is ubiquitous in quantum information science, from quantum
simulation to quantum metrology, including the quest for quantum supremacy via
the boson sampling problem. Within these contexts, the capability to learn
efficiently the unitary operation of the implemented interferometers becomes a
crucial requirement. In this letter we develop a reconstruction algorithm based
on a genetic approach, which can be adopted as a tool to characterize an
unknown linear optical network. We report an experimental test of the described
method by performing the reconstruction of a 7-mode interferometer implemented
via the femtosecond laser writing technique. Further applications of genetic
approaches can be found in other contexts, such as quantum metrology or
learning unknown general Hamiltonian evolutions.
