Direct Detection of Down-Converted Photons Spontaneously Produced at a Single Josephson Junction
Journal article, 2025

We study spontaneous photon decay into multiple photons triggered by strong nonlinearities in an experimental simulator of a bosonic quantum 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 multimode 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 3× the emission frequency. These results open exciting prospects for the burgeoning field of many-body quantum optics and offer a direct signature of the ultrastrong light-matter coupling.

Author

Dorian Fraudet

Grenoble Alpes University

Izak Snyman

University of Witwatersrand

Denis M. Basko

Laboratoire de Physique et Modélisation des Milieux Condensés

Sébastien Léger

Stanford University

Grenoble Alpes University

Théo Sépulcre

Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics

Arpit Ranadive

Grenoble Alpes University

Gwenael Le Gal

Grenoble Alpes University

Alba Torras-Coloma

Universitat Autonoma de Barcelona (UAB)

Institut de Física d'Altes Energies, Bellaterra

Wiebke Guichard

Grenoble Alpes University

Serge Florens

Grenoble Alpes University

Nicolas Roch

Grenoble Alpes University

Physical Review Letters

0031-9007 (ISSN) 1079-7114 (eISSN)

Vol. 134 1 013804

Subject Categories (SSIF 2025)

Atom and Molecular Physics and Optics

Condensed Matter Physics

Other Physics Topics

DOI

10.1103/PhysRevLett.134.013804

More information

Latest update

1/20/2025