Polarization entanglement with GRaded-INdex lenses

TL;DR

This paper demonstrates a simple, efficient optical device combining a GRIN lens and fiber that preserves polarization entanglement of photon pairs, facilitating integration into complex quantum optical systems.

Contribution

It introduces a novel, easy-to-align device that maintains polarization entanglement and enables high coupling efficiency for quantum photonic applications.

Findings

Preserves polarization entanglement during collection.

Achieves high coupling efficiency with simple alignment.

Suitable for complex quantum optical circuits.

Abstract

By using an optical device based on the integration of a GRaded-INdex (GRIN) rod lens and a single-mode optical fiber we efficiently collected photon pairs generated by spontaneous parametric down-conversion. We show that this system preserves the polarization entanglement of the 2-photon states. Hence this device, characterized by a remarkable easiness of alignment and allowing for high coupling efficiency of single-mode radiation, can be used with photons entangled in various degrees of freedom, such as polarization and spatial momentum, and to interconnect different sides of complex optical circuits.