Entanglement of Polarization and Orbital Angular Momentum

TL;DR

This paper explores the entanglement of two-photon states across polarization and orbital angular momentum degrees of freedom, proposing schemes for entanglement sorting and extending concepts to multi-photon states.

Contribution

It introduces entanglement duality and sorting schemes for polarization and OAM, and generalizes these ideas to multi-photon entangled states.

Findings

Successful entanglement detection using witnesses

Schemes for entanglement sorting based on OAM or polarization

Generalizations to three- and four-photon entangled states

Abstract

We investigate two-photon entangled states using two important degrees of freedom of the electromagnetic field, namely orbital angular momentum (OAM) and spin angular momentum. For photons propagating in the same direction we apply the idea of $\textit{entanglement duality}$ and develop schemes to do $\textit{entanglement sorting}$ based either on OAM or polarization. In each case the entanglement is tested using appropriate witnesses. We finally present generalizations of these ideas to three- and four-photon entangled states.