Generation and characterization of ultrabroadband polarization-frequency hyperentangled photons

TL;DR

This paper reports the generation of ultrabroadband polarization-frequency hyperentangled photons covering the C- and L-bands, with comprehensive characterization and demonstration of high-dimensional entanglement for quantum networking applications.

Contribution

It introduces an all-waveguided Sagnac source for ultrabroadband hyperentangled photons and demonstrates scalable high-dimensional entanglement in polarization and frequency.

Findings

Achieved full tomography of four-qubit systems in multiple channels.

Reconstructed states in a 36-dimensional Hilbert space.

Potential for enhanced quantum networking protocols.

Abstract

We generate ultrabroadband photon pairs entangled in both polarization and frequency bins through an all-waveguided Sagnac source covering the entire optical C- and L-bands (1530--1625 nm). We perform comprehensive characterization of high-fidelity states in multiple dense wavelength-division multiplexed channels, achieving full tomography of effective four-qubit systems. Additionally, leveraging the inherent high dimensionality of frequency encoding and our electro-optic measurement approach, we demonstrate the scalability of our system to higher dimensions, reconstructing states in a 36-dimensional Hilbert space consisting of two polarization qubits and two frequency-bin qutrits. Our findings hold potential significance for quantum networking, particularly dense coding and entanglement distillation in wavelength-multiplexed quantum networks.