Scattering of Photons and Limits of Ultrastrong Light-matter Coupling in Open Transmission Lines

Juan José García‐Ripoll

Vincenzo Macrí, Alberto Mercurio, Franco Nori +2 more

We show that spontaneous Raman scattering of incident radiation can be observed in cavity-QED systems without external enhancement or coupling to any vibrational degree of freedom. Raman scattering processes can be evidenced as resonances in the emission spectrum, which become clearly visible as the cavity-QED system approaches the ultrastrong coupling regime. We provide a quantum mechanical description of the effect, and show that ultrastrong light-matter coupling is a necessary condition for the observation of Raman scattering. This effect, and its strong sensitivity to the system parameters, opens new avenues for the characterization of cavity QED setups and the generation of quantum states of light

Anton Frisk Kockum, Adam Miranowicz, Simone De Liberato +2 more

Vincenzo Macrí, Alberto Mercurio, Franco Nori +2 more

We show that spontaneous Raman scattering of incident radiation can be observed in cavity-QED systems without external enhancement or coupling to any vibrational degree of freedom. Raman scattering processes can be evidenced as resonances in the emission spectrum, which become clearly visible as the cavity-QED system approaches the ultrastrong coupling regime. We provide a quantum mechanical description of the effect, and show that ultrastrong light-matter coupling is a necessary condition for the observation of Raman scattering. This effect, and its strong sensitivity to the system parameters, opens new avenues for the characterization of cavity QED setups and the generation of quantum states of light.

Agapi Emmanouilidou, L. E. Reichl

Dorian Fraudet, Izak Snyman, D. M. Basko +8 more

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.