Polarization-entangled photon pair sources based on spontaneous four wave mixing assisted by polarization mode dispersion

TL;DR

This paper demonstrates a novel method for generating high-fidelity polarization-entangled photon pairs directly in an integrated AlGaAs waveguide, leveraging polarization mode dispersion without additional compensation, advancing scalable quantum photonic technologies.

Contribution

It introduces a new approach to produce polarization-entangled photons in integrated waveguides using PMD, eliminating the need for compensation and enabling scalable quantum photonic circuits.

Findings

Achieved raw concurrence up to 0.91 in 1100-nm waveguide

Generated Bell states with fidelity of 0.90 in 800-nm waveguide

Demonstrated direct entangled photon pair generation without compensation

Abstract

Photonic-based qubits and integrated photonic circuits have enabled demonstrations of quantum information processing (QIP) that promises to transform the way in which we compute and communicate. To that end, sources of polarization-entangled photon pair states are an important enabling technology, especially for polarization-based protocols. However, such states are difficult to prepare in an integrated photonic circuit. Scalable semiconductor sources typically rely on nonlinear optical effects where polarization mode dispersion (PMD) degrades entanglement. Here, we directly generate polarization-entangled states in an AlGaAs waveguide, aided by the PMD and without any compensation steps. We perform quantum state tomography and report a raw concurrence as high as 0.91$\pm$0.01 observed in the 1100-nm-wide waveguide. The scheme allows direct Bell state generation with an observed maximum fidelity of 0.90$\pm$0.01 from the 800-nm-wide waveguide. Our demonstration paves the way for sources that allow for the implementation of polarization-encoded protocols in large-scale quantum photonic circuits.