We demonstrate that important information about linear optical circuits can be obtained through the phase shift induced by integrated optical resonators. As a proof of principle, the phase of an unbalanced Mach-Zehnder interferometer is determined. Then the method is applied to a complex optical circuit designed for linear optical quantum computation. In this controlled-NOT gate with qubit initialization and tomography stages, the relative phases are determined as well as the coupling ratios of its directional couplers.
@article{arxiv.1609.02676,
title = {Characterization of optical quantum circuits using resonant phase shifts},
author = {Menno Poot and Hong X. Tang},
journal= {arXiv preprint arXiv:1609.02676},
year = {2016}
}