Metasurface quantum graphs for generalized Hong-Ou-Mandel interference
Kerolos M. A. Yousef, Marco D’Alessandro, Matthew Yeh, Neil Sinclair, Marko Lončar, Federico Capasso
Abstract
Multiphoton interference and entanglement are fundamental to quantum information science, yet extending these effects to higher-dimensional systems remains challenging given the imperfections and complexity of scaling conventional linear-optical setups. We present a generalized Hong-Ou-Mandel effect using metasurfaces and graph theory, achieving controlled multiphoton bunching, antibunching, and entanglement across parallel Jones matrix-encoded spatial modes-all within a single-layer metasurface. A graph-theoretic dual framework is introduced that simultaneously encodes the metasurface-based multiport interferometer designs and its resulting nonclassical correlations, enabling the direct translation of linear quantum optical networks into a single-layer metasurface. We also demonstrate the ability of metasurfaces to produce multipath-entangled states and perform transformations equivalent to higher-order Hadamard interferometers. Our results underscore metasurface quantum graphs for scalable, low-decoherence quantum information infrastructure.