High-dimensional discrete Fourier transform gates with the quantum frequency processor

TL;DR

This paper demonstrates a scalable method to implement high-dimensional discrete Fourier transform gates using a quantum frequency processor, enabling advanced quantum communication protocols.

Contribution

It introduces a fixed three-component quantum frequency processor for high-dimensional DFTs, verified through simulations and experiments up to dimension 3.

Findings

Achieved high fidelity (>0.9997) and success probability (>0.965) in simulations for dimensions up to 10.

Experimentally implemented the method for dimension 3, enabling entanglement measurement and state tomography.

Provides a scalable approach for high-dimensional quantum frequency-bin operations in quantum information.

Abstract

The discrete Fourier transform (DFT) is of fundamental interest in photonic quantum information, yet the ability to scale it to high dimensions depends heavily on the physical encoding, with practical recipes lacking in emerging platforms such as frequency bins. In this Letter, we show that d-point frequency-bin DFTs can be realized with a fixed three-component quantum frequency processor (QFP), simply by adding to the electro-optic modulation signals one radio-frequency harmonic per each incremental increase in d. We verify gate fidelity F > 0.9997 and success probability P > 0.965 up to d = 10 in numerical simulations, and experimentally implement the solution for d = 3, utilizing measurements with parallel DFTs to quantify entanglement and perform full tomography of multiple two-photon frequency-bin states. Our results furnish new opportunities for high-dimensional frequency-bin protocols in quantum communications and networking.