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arXiv · 2408.15304

Single-photon description of the lossless optical Y coupler

Christopher R. Schwarze·Anthony D. Manni·David S. Simon·Alexander V. Sergienko
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Abstract

Using symmetry considerations, we derive a unitary scattering matrix for a three-port optical Y-coupler or Y-branch. The result is shown to be unique up to external phase shifts. Unlike traditional passive linear-optical one-way splitters, coupling light into the conventional output ports of the Y-coupler results in strong coherent back-reflections, making the device a hybrid between feed-forward devices like the beam splitter, which do not reverse the direction of light, and a recently considered class of directionally unbiased multiport scatterers (with dimension greater than two) which do. While the device could immediately find use as a novel scattering vertex for the implementation of quantum walks, we also design a few simple but nonetheless useful optical systems that can be constructed by taking advantage of the symmetry of the scattering process. This includes an interference-free, resource-efficient implementation of the Grover four-port and a higher-dimensional Fabry-Perot interferometer with tunable finesse. Symmetry-breaking generalizations are also considered.

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Christopher R. Schwarze, Anthony D. Manni, David S. Simon, Alexander V. Sergienko. 2024-08-27. Single-photon description of the lossless optical Y coupler. https://doi.org/10.1103/physreva.110.023527

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