The ability to apply user-chosen large-scale unitary operations with high fidelity to a quantum state is key to realizing future photonic quantum technologies. Here, we realize the implementation of programmable unitary operations on up to 64 frequency-bin modes. To benchmark the performance of our system, we probe different quantum walk unitary operations, in particular Grover walks on four-dimensional hypercubes with similarities exceeding 95\% and quantum walks with 400 steps on circles and finite lines with similarities of 98\%. Our results open a new path towards implementing high-quality unitary operations, which can form the basis for applications in complex tasks, such as Gaussian boson sampling.
@article{arxiv.2206.06059,
title = {Realization of high-fidelity unitary operations on up to 64 frequency bins},
author = {Syamsundar De and Vahid Ansari and Jan Sperling and Sonja Barkhofen and Benjamin Brecht and Christine Silberhorn},
journal= {arXiv preprint arXiv:2206.06059},
year = {2024}
}