The Bright Side of Coulomb Blockade

TL;DR

This paper investigates the emission of photons from a Josephson junction under Coulomb blockade, revealing regimes where Cooper pairs emit one or two photons, extending existing theory to explain the spectral properties of emitted radiation.

Contribution

It introduces an experimental study of photon emission in dynamical Coulomb blockade, demonstrating regimes of single and double photon emission and extending DCB theory to spectral analysis.

Findings

Cooper pairs emit one or two photons into the resonator.

Photon emission rates correlate with Cooper pair tunneling.

Spectral properties match extended DCB theoretical predictions.

Abstract

We explore the photonic (bright) side of dynamical Coulomb blockade (DCB) by measuring the radiation emitted by a dc voltage-biased Josephson junction embedded in a microwave resonator. In this regime Cooper pair tunneling is inelastic and associated to the transfer of an energy 2eV into the resonator modes. We have measured simultaneously the Cooper pair current and the photon emission rate at the resonance frequency of the resonator. Our results show two regimes, in which each tunneling Cooper pair emits either one or two photons into the resonator. The spectral properties of the emitted radiation are accounted for by an extension to DCB theory.