arXiv:2106.13426 · Physical Review A
Polarization rotation and near-Earth quantum communications
Pravin Kumar Dahal, Daniel R. Terno
Abstract
We revisit polarization rotation due to gravity, known as the gravitational Faraday effect, with a view on its role in quantum communications with Earth-orbiting satellites. In a static spherically symmetric gravitational field Faraday rotation is purely a reference frame (gauge) effect. This is so also in the leading post-Newtonian expansion of the Earth's gravitational field. However, establishing the local reference frame with respect to distant stars leads to the nonzero Faraday phase. In communications between a ground station and an Earth-orbiting spacecraft this phase is of the order of ${10}^{\ensuremath{-}10}$. Under the same conditions the Wigner phase of special relativity is typically of the order ${10}^{\ensuremath{-}4}\ensuremath{-}{10}^{\ensuremath{-}5}$. These phases lead to the physical lower bound on communication errors. However, both types of errors can be simultaneously mitigated. Moreover, they are countered by a fully reference frame independent scheme that also handles arbitrary misalignments between the reference frames of sender and receiver.