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arXiv · 2605.14314

Quantum optical synthesis of high-dimensional ultrafast frequency-bin qudits

Prasad Koviri·Tomoya Okita·Rina Yabumoto·Yuta Fujihashi·Masahiro Yabuno·Hirotaka Terai·Shigehito Miki·Kali P. Nayak·Ryosuke Shimizu
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Abstract

Frequency modes of light are one of the most promising platforms that provide access to high-dimensional quantum states amongst different photonic degrees of freedom capable of high-dimensionality, enabling robust, error-tolerant, and scalable quantum optical information systems. We demonstrate engineering of precisely controlled two-photon high-dimensional states entangled in frequency through time-domain Fourier optical synthesis. We generate and convert a continuous broadband frequency-entangled state into a large range of discrete frequency bins suitable for ITU standards, with spacings ranging from 12.5 GHz to 750 GHz, and observe spectral anticorrelations over 38 frequency bins, including intra-bin pure states at a 100 GHz bin spacing. We characterize the full quantum state dimensionality via Schmidt decomposition and observe lower bounds on the frequency-binned Hilbert-space dimensionalities of at least 289, formed by two entangled qudits with dimension 17. Furthermore, we demonstrate quantum nonlocality via frequency correlations in a transmission experiment over a campus-scale two-node fiber network. This work represents a crucial step towards building a versatile and relatively simple way of generating precisely controlled high-dimensional spectral qudits, with the potential of harnessing in wavelength-multiplexed quantum networks, high-dimensional information processing, and communication of quantum states specifically, and fiber-optic quantum remote sensing.

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Prasad Koviri, Tomoya Okita, Rina Yabumoto, Yuta Fujihashi, Masahiro Yabuno, Hirotaka Terai, Shigehito Miki, Kali P. Nayak, Ryosuke Shimizu. 2026-05-14. Quantum optical synthesis of high-dimensional ultrafast frequency-bin qudits. https://arxiv.org/abs/2605.14314

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