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Letter - Direct characterization of a nonlinear photonic circuit's wave function with laser light




Lenzini, Francesco
Poddubny, Alexander
Titchener, James
Fisher, Paul
Boes, Andreas
Kasture, Sachin
Haylock, Ben
Villa, Matteo
Mitchell, Arnan
Solntsev, Alexander

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Springer Nature


Integrated photonics is a leading platform for quantum technologies including nonclassical state generation1, 2, 3, 4, demonstration of quantum computational complexity5 and secure quantum communications6. As photonic circuits grow in complexity, full quantum tomography becomes impractical, and therefore an efficient method for their characterization7, 8 is essential. Here we propose and demonstrate a fast, reliable method for reconstructing the two-photon state produced by an arbitrary quadratically nonlinear optical circuit. By establishing a rigorous correspondence between the generated quantum state and classical sum-frequency generation measurements from laser light, we overcome the limitations of previous approaches for lossy multi-mode devices9, 10. We applied this protocol to a multi-channel nonlinear waveguide network and measured a 99.28±0.31% fidelity between classical and quantum characterization. This technique enables fast and precise evaluation of nonlinear quantum photonic networks, a crucial step towards complex, large-scale, device production.



Nonlinear optics, Quantum optics, Single photons and quantum effects



Light: Science & Applications


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Open Access

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This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the materialis not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material.



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