Inelastic Microwave Photon Scattering off a Quantum Impurity in a Josephson-Junction Array

TL;DR

This paper investigates how quantum impurities in Josephson-junction arrays cause inelastic microwave photon scattering, revealing many-body Kondo physics effects that are difficult to observe in fermionic systems.

Contribution

It demonstrates that a quantum impurity in a Josephson array exhibits Kondo physics and analyzes its impact on photon scattering, highlighting novel many-body phenomena in a photonic context.

Findings

Quantum impurity shows Kondo behavior.

Elastic and inelastic scattering cross sections calculated.

Many-body properties accessible via photon scattering.

Abstract

Quantum fluctuations in an anharmonic superconducting circuit enable frequency conversion of individual incoming photons. This effect, linear in the photon beam intensity, leads to ramifications for the standard input-output circuit theory. We consider an extreme case of anharmonicity in which photons scatter off a small set of weak links within a Josephson junction array. We show that this quantum impurity displays Kondo physics and evaluate the elastic and inelastic photon scattering cross sections. These cross sections reveal many-body properties of the Kondo problem that are hard to access in its traditional fermionic version.