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arXiv · 2405.00411

Direct detection of down-converted photons spontaneously produced at a single Josephson junction

Dorian Fraudet·Izak Snyman·Denis M. Basko·Sébastien Léger·Théo Sépulcre·Arpit Ranadive·Gwenael Le Gal·Alba Torras-Coloma·Serge Florens·Nicolas Roch
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Abstract

We study spontaneous photon decay into multiple photons triggered by strong non-linearities in a superconducting quantum simulator of the boundary sine-Gordon impurity model. Previously, spectroscopic signatures of photon-conversion were reported and evidenced as resonances in the many-body spectrum of these systems. Here, we report on the observation of multi-mode fluorescence of a small Josephson junction embedded in a high impedance superconducting transmission line. Measurement of the down-converted photons is achieved using state-of-the-art broadband parametric amplifiers. Photon triplet emission is explicitly demonstrated at a given frequency as the counterpart of inelastic photon decay at three-times the emission frequency. These results open exciting prospects for the burgeoning field of many-body quantum optics and offer a direct signature of the ultra-strong light-matter coupling.

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Dorian Fraudet, Izak Snyman, Denis M. Basko, Sébastien Léger, Théo Sépulcre, Arpit Ranadive, Gwenael Le Gal, Alba Torras-Coloma, Serge Florens, Nicolas Roch. 2024-05-01. Direct detection of down-converted photons spontaneously produced at a single Josephson junction. https://doi.org/10.1103/physrevlett.134.013804

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