Electron-photon coupling in Mesoscopic Quantum Electrodynamics

TL;DR

This paper develops a formalism to describe the interaction between cavity photons and electrons in nanocircuits, bridging atomic cavity QED and superconducting circuit QED, enabling analysis of photon-induced electronic effects.

Contribution

A novel photonic pseudo-potential method is introduced to model electric coupling in mesoscopic QED systems, accommodating complex nanocircuit geometries and interactions.

Findings

Photon-induced tunneling causes non-universal cavity frequency shifts.

The formalism applies to various nanostructures including quantum dots and Majorana systems.

Photon coupling can induce orbital energy shifts and local transitions.

Abstract

Understanding the interaction between cavity photons and electronic nanocircuits is crucial for the development of Mesoscopic Quantum Electrodynamics (QED). One has to combine ingredients from atomic Cavity QED, like orbital degrees of freedom, with tunneling physics and strong cavity field inhomogeneities, specific to superconducting circuit QED. It is therefore necessary to introduce a formalism which bridges between these two domains. We develop a general method based on a photonic pseudo-potential to describe the electric coupling between electrons in a nanocircuit and cavity photons. In this picture, photons can induce simultaneously orbital energy shifts, tunneling, and local orbital transitions. We study in details the elementary example of a single quantum dot with a single normal metal reservoir, coupled to a cavity. Photon-induced tunneling terms lead to a non-universal relation between the cavity frequency pull and the damping pull. Our formalism can also be applied to multi quantum dot circuits, molecular circuits, quantum point contacts, metallic tunnel junctions, and superconducting nanostructures enclosing Andreev bound states or Majorana bound states, for instance.