We demonstrate high-fidelity, tunable, and ultrafine-resolution on-chip frequency beamsplitters using a quantum frequency processor based on an integrated pulse shaper with six spectral channels. Near-ideal Hadamard gate performance is achieved, with fidelity F > 0.9995 and modified success probability P > 0.9621 maintained across frequency spacings from 2-5 GHz and down to as few as four spectral pulse shaper channels. The system's support of frequency spacings as narrow as 2 GHz significantly surpasses prior bulk demonstrations and enables arbitrary splitting ratios via spectral phase or modulation index control. These results establish a scalable and resource-efficient platform for integrated frequency-bin quantum photonics, opening new directions in quantum information processing, including densely parallel single-qubit operations and multidimensional gate implementations.
@article{arxiv.2601.23028,
title = {High-resolution tunable frequency beamsplitter enabled by an integrated silicon pulse shaper},
author = {Chen-You Su and Kaiyi Wu and Lucas M. Cohen and Saleha Fatema and Navin B. Lingaraju and Hsuan-Hao Lu and Andrew M. Weiner and Joseph M. Lukens and Jason D. McKinney},
journal= {arXiv preprint arXiv:2601.23028},
year = {2026}
}