Shaping frequency entangled qudits

TL;DR

This paper demonstrates the creation, characterization, and manipulation of high-dimensional frequency-entangled qudits up to dimension 4, advancing quantum information processing capabilities.

Contribution

It introduces a method to shape the energy spectrum of entangled photons to generate and analyze high-dimensional frequency qudits, including density matrix reconstruction.

Findings

Successfully created and characterized qudits up to dimension 4.

Measured Bell parameters for qubits, qutrits, and ququads.

Showed control over entanglement in high-dimensional frequency states.

Abstract

Quantum entanglement between qudits - the d-dimensional version of qubits - is relevant for advanced quantum information processing and provides deeper insights in the nature of quantum correlations. Encoding qudits in the frequency modes of photon pairs produced by continuous parametric down-conversion enables access to high-dimensional states. By shaping the energy spectrum of entangled photons, we demonstrate the creation, characterization and manipulation of entangled qudits with dimension up to 4. Their respective density matrices are reconstructed by quantum state tomography. For qubits and qutrits we additionally measured the dependency of a d-dimensional Bell parameter for various degrees of entanglement. Our experiment demonstrates the ability to investigate the physics of high-dimensional frequency entangled qu$d$it states which are of great importance for quantum information science.