Transmission of quantum entanglement through a random medium

TL;DR

This paper investigates how high-dimensional quantum entanglement is affected when photons pass through a random medium, revealing that entanglement can be reduced or recovered depending on mode access, with implications for quantum communication.

Contribution

It demonstrates how entanglement degrades or can be restored in a random medium by controlling the number of transmitted modes, providing new insights into quantum state transmission.

Findings

Multiple scattering reduces entanglement of maximally entangled states.

Accessing more transmitted modes can recover near-original entanglement.

Separable states do not gain entanglement after transmission.

Abstract

We study the high-dimensional entanglement of a photon pair transmitted through a random medium. We show that multiple scattering in combination with the subsequent selection of only a fraction of outgoing modes reduces the average entanglement of an initially maximally entangled two-photon state. Entanglement corresponding to a random pure state is obtained when the number of modes accessible in transmission is much less than the number of modes in the incident light. An amount of entanglement approaching that of the incident light can be recovered by accessing a larger number of transmitted modes. In contrast, a pair of photons in a separable state does not gain any entanglement when transmitted through a random medium.