Coherence and dimensionality witnesses for fractional orbital angular momentum modes
Phys. Rev. A 113, 043512 – Published 13 April, 2026
DOI: https://doi.org/10.1103/v17y-w1lm
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.
