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APL Photonics

Near-unity quantum interference of transverse spatial modes in an ultra-compact inverse-designed photonic device

Jamika Ann Roque, Daniel Peace, Simon White, Emanuele Polino, Sayantan Das, Farzad Ghafari, Sergei Slussarenko, Nora Tischler, Jacquiline Romero

Published Feb 1, 2026• 0 citations

Abstract

Transverse spatial modes as a degree of freedom is an untapped resource for scaling up integrated photonic quantum computing. To be practically useful for improving scalability, reliable and high-visibility quantum interference between transverse spatial modes on-chip needs to be demonstrated. We show repeatable quantum interference using inverse-designed transverse mode beam splitters that have an ultra-compact footprint of 3 × 3 μm2—the smallest transverse mode beam splitters for 1550 nm photons to date. We measure a Hong–Ou–Mandel visibility of up to 99.56% ± 0.62% from a single device, with an average visibility across three identical devices of 99.38% ± 0.41%, indicating a high degree of reproducibility. Our work demonstrates that inverse-designed components are suitable for engineering quantum interference on-chip of multimode devices, paving the way for future compact integrated quantum photonic devices that exploit transverse spatial modes as a degree of freedom for high-dimensional quantum information.

DOI: 10.1063/5.0299808

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