  We employed an electrically-driven polarization controller to implement
anisotropic depolarizing quantum channels for the polarization state of single
photons. The channels were characterized by means of ancilla-assisted quantum
process tomography using polarization-entangled photons generated in the
process of spontaneous parametric down-conversion. The demonstrated
depolarization method offers good repeatability, low cost, and compatibility
with fiber-optic setups. It does not perturb the modal structure of single
photons, and therefore can be used to verify experimentally protocols for
managing decoherence effects based on multiphoton interference.
