An Exact Expression for Photon Polarization in Kerr Geometry

Understand

We analyze the transformation of the polarization of a photon propagating along an arbitrary null geodesic in Kerr geometry.

• The motivation comes from the problem of an observer trying to communicate quantum information to another observer in Kerr spacetime by transmitting polarized photons.
• It is essential that the observers understand the relationship between their frames of reference and also know how the photon's polarization transforms as it travels through Kerr spacetime.
• Existing methods to calculate the rotation of the photon polarization (Faraday rotation) depend on choices of coordinate systems, are algebraically complex and yield results only in the weak-field limit.