Generation and characterization of ultrabroadband polarization-frequency hyperentangled photons

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.

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• On-chip frequency-bin quantum photonics
• Building a controlled-NOT gate between polarization and frequency
• Procrustean entanglement concentration in quantum-classical networking
• Quantum nonlocal modulation cancellation with distributed clocks
• Generation of hyperentangled photon pairs in the time and frequency domain on a silicon photonic chip
• Photonic hyperentanglement in polarisation and frequency via joint spectrum shaping