We propose a single-photon-by-single-photon all-optical switch concept based on interference-localized states on lattices and their delocalization by interaction. In its “open” operation, the switch stops single photons while allows photon pairs to pass the switch. Alternatively, in the “closed” operation, the switch geometrically separates single-photon and two-photon states. We demonstrate the concept using a three-site Stub unit cell and the diamond chain. The systems are modeled by Bose-Hubbard Hamiltonians, and the dynamics is solved by exact diagonalization with Lindblad master equation. We discuss realization of the switch using photonic lattices with nonlinearities, superconductive qubit arrays, and ultracold atoms. We show that the switch allows arbitrary “ON”/“OFF” contrast while achieving picosecond switching time at the single-photon switching energy with contemporary photonic materials.

• Received 16 August 2023
• Accepted 27 November 2023

DOI:https://doi.org/10.1103/PhysRevResearch.5.043259

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Published by the American Physical Society