Entanglement-assisted polarimeter for phase retardance measurement

Polarimeter is a vital precision tool used for measuring optical parameters through polarization variations.Among the wide range of application fields, the precise measurement of photosensitive materials is an unavoidable task but faces immense obstacles due to the excessive input photons.Facing this situation, introducing a quantum source into the classical precision measurement system is a feasible way to enhance the detection accuracy under the low illumination regime.In this work, we employ polarization-entangled photon pairs in the classical polarimeter to precisely detect the relative phase retardance of uniform anisotropic media.The experimental results show that the accuracy can reach the nanometer scale at extremely low input intensity, and the stabilities are within 0.4% for all samples.Our work paves the way for polarization measurement at low incident light intensity, with potential applications in measuring photosensitive materials and remote monitoring scenarios.