Renormalization and Low-Energy Effective Models in Cavity and Circuit QED

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Main Authors: Lamberto, Daniele, Mercurio, Alberto, Di Stefano, Omar, Savona, Vincenzo, Savasta, Salvatore
Format: Preprint
Published: 2025
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author Lamberto, Daniele
Mercurio, Alberto
Di Stefano, Omar
Savona, Vincenzo
Savasta, Salvatore
author_facet Lamberto, Daniele
Mercurio, Alberto
Di Stefano, Omar
Savona, Vincenzo
Savasta, Salvatore
contents The quantum Rabi model (QRM) is a cornerstone in the study of light-matter interactions within cavity and circuit quantum electrodynamics (QED). It effectively captures the dynamics of a two-level system coupled to a single-mode resonator, serving as a foundation for understanding quantum optical phenomena in a great variety of systems. However, this model may produce inaccurate results for large coupling strengths, even in systems with high anharmonicity. Moreover, issues of gauge invariance further undermine its reliability. In this work, we introduce a renormalized QRM that incorporates the effective influence of higher atomic energy levels, providing a significantly more accurate representation of the system while still maintaining a two-level description. To demonstrate the versatility of this approach, we present two different examples: an atom in a double-well potential and a superconducting artificial atom (fluxonium qubit). This procedure opens new possibilities for precisely engineering and understanding cavity and circuit QED systems, which are highly sought-after, especially for quantum information processing.
format Preprint
id arxiv_https___arxiv_org_abs_2503_01651
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Renormalization and Low-Energy Effective Models in Cavity and Circuit QED
Lamberto, Daniele
Mercurio, Alberto
Di Stefano, Omar
Savona, Vincenzo
Savasta, Salvatore
Quantum Physics
The quantum Rabi model (QRM) is a cornerstone in the study of light-matter interactions within cavity and circuit quantum electrodynamics (QED). It effectively captures the dynamics of a two-level system coupled to a single-mode resonator, serving as a foundation for understanding quantum optical phenomena in a great variety of systems. However, this model may produce inaccurate results for large coupling strengths, even in systems with high anharmonicity. Moreover, issues of gauge invariance further undermine its reliability. In this work, we introduce a renormalized QRM that incorporates the effective influence of higher atomic energy levels, providing a significantly more accurate representation of the system while still maintaining a two-level description. To demonstrate the versatility of this approach, we present two different examples: an atom in a double-well potential and a superconducting artificial atom (fluxonium qubit). This procedure opens new possibilities for precisely engineering and understanding cavity and circuit QED systems, which are highly sought-after, especially for quantum information processing.
title Renormalization and Low-Energy Effective Models in Cavity and Circuit QED
topic Quantum Physics
url https://arxiv.org/abs/2503.01651