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arXiv · 2509.13275

Coherence and Dimensionality Witnesses for Fractional OAM Modes

A. L. S. Santos Junior·I. Prego·M. Gil de Oliveira·A. C. Barbosa·B. P. da Silva·D. J. Brod·E. F. Galvão·A. Z. Khoury
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Abstract

We characterize sets of fractional orbital angular momentum (OAM) modes of a light beam using unitary-invariant properties encoded by two-mode overlaps. Using basis-independent coherence and dimension witnesses, we experimentally certify, on a triple of fractional modes, both the presence of coherence and that the states necessarily span a space of dimension 3. We propose and implement a practical, fast experimental method to extract two-mode overlaps requiring only a single intensity image per interference pair. These results lay the groundwork for using fractional OAM states in high-dimensional quantum information protocols.

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A. L. S. Santos Junior, I. Prego, M. Gil de Oliveira, A. C. Barbosa, B. P. da Silva, D. J. Brod, E. F. Galvão, A. Z. Khoury. 2025-09-16. Coherence and Dimensionality Witnesses for Fractional OAM Modes. https://arxiv.org/abs/2509.13275

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