Depolarization is one of the most important sources of error in a quantum communication link that can be introduced by the quantum channel. Even though standard quantum process tomography can, in theory, be applied to characterize this effect, in most real-world implementations depolarization cannot be distinguished from time-varying unitary transformations, especially when the time scales are much shorter than the detectors response time. In this paper, we introduce a method for distinguishing true depolarization from fast polarization rotations by employing Hong-Ou-Mandel interference. It is shown that the results are independent of the timing resolutions of the photodetectors.
@article{arxiv.1905.08080,
title = {Characterization of Depolarizing Channels Using Two-Photon Intereference},
author = {Gustavo C. Amaral and Guilherme P. Temporão},
journal= {arXiv preprint arXiv:1905.08080},
year = {2019}
}