Quadratic Quantum Polarimetry with Entangled Photon Pairs

TL;DR

This paper introduces a quadratic quantum polarimetry method using entangled photon pairs that probes depolarizing media simultaneously, revealing second-order polarization information and enhanced sensitivity over traditional methods.

Contribution

It develops a theoretical framework linking Mueller matrices to two-photon polarization correlations and demonstrates experimental validation of higher-order quantum polarimetry.

Findings

Quadratic degradation of entanglement indicates depolarization effects.

Two-photon probing shows increased sensitivity to polarization scrambling.

Experimental results match theoretical predictions for polarization channel characterization.

Abstract

Conventional polarimetry, including schemes leveraging entangled light, characterizes optical samples through linear transformations of polarization states. We introduce a two-photon probing approach in which both photons of an entangled pair interact with the same depolarizing medium simultaneously. In this regime, the transformation of the two-photon polarization correlations becomes quadratic in the Mueller matrix, enabling access to second-order polarization information beyond conventional polarimetry. We develop a theoretical framework linking the Mueller matrix to the evolution of the two-photon polarization correlation tensor and show that depolarization induces quadratic degradation of entanglement and state purity. Experiments using polarization-entangled photon pairs transmitted through controlled scattering media confirm the predicted response and reveal enhanced sensitivity to polarization scrambling compared with single-photon probing. These results establish two-photon probing as a higher-order quantum polarimetric modality for characterizing polarization channels.