We provide a statistically robust and accurate framework to measure and track the polarisation state of light employing Hong-Ou-Mandel interference. This is achieved by combining the concepts of maximum likelihood estimation and Fisher information applied to photon detection events. Such an approach ensures that the Cram\'er-Rao bound is saturated and changes to the polarisation state are established in an optimal manner. Using this method, we show that changes in the linear polarisation state can be measured with 0.6 arcminute precision (0.01 degrees).
@article{arxiv.1912.12087,
title = {Tracking the polarisation state of light via Hong-Ou-Mandel interferometry},
author = {Natapon Harnchaiwat and Feng Zhu and Niclas Westerberg and Erik Gauger and Jonathan Leach},
journal= {arXiv preprint arXiv:1912.12087},
year = {2020}
}