Quantum information transfer from spin to orbital angular momentum of photons

TL;DR

This paper demonstrates the experimental transfer of quantum information between photon polarization and orbital angular momentum using a q-plate, enabling a bidirectional quantum interface for information transposition.

Contribution

It provides the first experimental realization of a spin-OAM quantum interface, transferring quantum states and correlations between these degrees of freedom.

Findings

Successful transfer of single-photon quantum states via quantum tomography

Transfer of two-photon quantum correlations like coalescence interference

Validation of a bidirectional spin-OAM quantum interface

Abstract

The optical "spin-orbit" coupling occurring in a suitably patterned nonuniform birefringent plate known as `q-plate' allows entangling the polarization of a single photon with its orbital angular momentum (OAM). This process, in turn, can be exploited for building a bidirectional "spin-OAM interface", capable of transposing the quantum information from the spin to the OAM degree of freedom of photons and \textit{vice versa}. Here, we experimentally demonstrate this process by single-photon quantum tomographic analysis. Moreover, we show that two-photon quantum correlations such as those resulting from coalescence interference can be successfully transferred into the OAM degree of freedom.