Polarization state of a light field is an important property in many experimental situations. For example, it may limit the visibility of interference between two field modes, or it can be used to encode information to be transferred from Alice to Bob. However, in a long distance fiber link, the polarization state of the field gets distorted inevitably.

In the proposed research topic two relevant cases should be studied: (1) polarization control in homodyne detection, when a strong local oscillator interferes with a weak signal field; (2) polarization control of a very weak field, i.e. a stream of single photons. In both cases the light fields  are transferred through a long single mode optical fiber.

The task of the candidate is to model the distortion of the polarization state of an injected field while traversing through the fiber. Then work out procedures to restore the polarization state at the output of the fiber in the two special cases described above. In case of promising methods it will be possible to try them out in practice in real quantum communication systems.