Josephson-Kondo screening cloud in circuit quantum electrodynamics

TL;DR

This paper demonstrates how a circuit-QED setup with a Cooper pair box and Josephson junction chain can be used to observe the Kondo screening cloud through charge susceptibility measurements, revealing universal and many-body features.

Contribution

It introduces a novel method to probe the Kondo screening cloud in circuit-QED systems using non-local polarization response and provides analytical and numerical insights into the spatial correlations involved.

Findings

Universal decay lineshape of charge susceptibility at moderate impedance

Spatial correlations indicative of many-body states at high impedance

Analytical and numerical results linking circuit response to Kondo physics

Abstract

We show that the non-local polarization response in a multimode circuit-QED setup, devised from a Cooper pair box coupled to a long chain of Josephson junctions, provides an alternative route to access the elusive Kondo screening cloud. For moderate circuit impedance, we compute analytically the universal lineshape for the decay of the charge susceptibility along the circuit, that relates to spatial entanglement between the qubit and its electromagnetic environment. At large circuit impedance, we numerically find further spatial correlations that are specific to a true many-body state.