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; Wiebke Guichard; Serge Florens; Nicolas Roch

doi:10.1103/PhysRevLett.134.013804

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, Wiebke Guichard, Serge Florens, Nicolas Roch

DOI 10.1103/PhysRevLett.134.013804 · Physical Review Letters

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Abstract

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.

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Formula	Reported Tc (K)	Pressure (GPa)	Type
Al Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Pb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Sn Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown