We demonstrate a Bell state analyzer that operates directly on frequency mismatch. Based on electro-optic modulators and Fourier-transform pulse shapers, our quantum frequency processor design implements interleaved Hadamard gates in discrete frequency modes. Experimental tests on entangled-photon inputs reveal accuracies of ∼98\% for discriminating between the ∣Ψ+⟩ and ∣Ψ−⟩ frequency-bin Bell states. Our approach resolves the tension between wavelength-multiplexed state transport and high-fidelity Bell state measurements, which typically require spectral indistinguishability.
@article{arxiv.2109.06385,
title = {Bell state analyzer for spectrally distinct photons},
author = {Navin B. Lingaraju and Hsuan-Hao Lu and Daniel E. Leaird and Steven Estrella and Joseph M. Lukens and Andrew M. Weiner},
journal= {arXiv preprint arXiv:2109.06385},
year = {2022}
}