Detection of persistent current correlation in cavity-QED

TL;DR

This paper models the spectral response of a cavity-QED system coupled to a magnetic flux-pierced ring with quantum dots, revealing how persistent current fluctuations influence microwave resonator properties.

Contribution

It introduces a theoretical framework combining Green function techniques and linear response theory to analyze persistent current dynamics in a cavity-QED setup with quantum dots.

Findings

Resonator frequency shifts depend on current fluctuations and coupling transparency.

Symmetric and asymmetric persistent current components have distinct spectral signatures.

Characteristic shifts and avoided crossings in the resonator response reveal current dynamics.

Abstract

We simulated the radiative response of the cavity quantum electrodynamics (QED) inductively coupled to the ring pierced by magnetic flux, and analyzed its spectral dependence to get insight into persistent current dynamics. Current fluctuations in the ring induce changes in the microwave resonator: shifting the resonant frequency and changing its damping. We use the linear response theory and calculate the current response function by means of the Green function technique. Our model contains two quantum dots which divide the ring into two arms with different electron transfers. There are two opposite (symmetric and asymmetric) components of the persistent current, which interplay can be observed in the response functions. The resonator reflectance shows characteristic shifts in the dispersive regime and avoided crossings at the resonance points. The magnitude of the resonator frequency shift is greater for coupling to the arm with higher transparency. Fluctuations of the symmetric component of the persistent current are relevant for a wide range of the Aharovov-Bohm phase $\phi$, while the asymmetric component becomes dominant close to $\phi\approx \pi$ (when the total persistent current changes its orientation)