Coherent Backscattering of Entangled Photon Pairs

TL;DR

This study demonstrates that entangled photon pairs maintain partial correlations after scattering in dynamic complex media, with enhanced correlations arising from interference effects similar to classical coherent backscattering, opening new avenues for entanglement transport.

Contribution

It reveals that entangled photons can retain correlations after multiple scattering in dynamic media, supported by experiments, simulations, and theoretical analysis of interference effects.

Findings

Enhanced correlations within a specific angular range

Correlations persist despite dynamic scattering

Interference between scattering trajectories causes enhancement

Abstract

Correlations between entangled photons are a key ingredient for testing fundamental aspects of quantum mechanics and an invaluable resource for quantum technologies. However, scattering from a dynamic medium typically scrambles and averages out such correlations. Here we show that multiply-scattered entangled photons reflected from a dynamic complex medium remain partially correlated. We observe in experiments and in full-wave simulations enhanced correlations, within an angular range determined by the transport mean free path, which prevail disorder averaging. Theoretical analysis reveals that this enhancement arises from the interference between scattering trajectories, in which the photons leave the sample and are then virtually reinjected back into it. These paths are the quantum counterpart of the paths that lead to the coherent backscattering of classical light. This work points to opportunities for entanglement transport despite dynamic multiple scattering in complex systems.