Renormalization and low-energy effective models in cavity and circuit quantum electrodynamics

Area of Science:

• Quantum physics
• Quantum optics
• Condensed matter physics

Background:

• The quantum Rabi model (QRM) is fundamental for studying light-matter interactions in cavity and circuit quantum electrodynamics (QED).
• The standard QRM exhibits inaccuracies at large coupling strengths and issues with gauge invariance.
• Accurate modeling is crucial for quantum information processing and understanding quantum optical phenomena.

Purpose of the Study:

• To introduce a renormalized quantum Rabi model (QRM) that accurately accounts for higher atomic energy levels.
• To provide a more reliable description of light-matter interactions, especially under strong coupling conditions.
• To demonstrate the applicability of the renormalized QRM in diverse quantum systems.

Main Methods:

• Development of a renormalized quantum Rabi model (QRM) incorporating effective higher-level atomic influences.
• Application of the renormalized QRM to a two-level system coupled to a single-mode resonator.
• Validation through case studies involving an atom in a double-well potential and a superconducting fluxonium qubit.

Main Results:

• The renormalized QRM offers a more accurate representation of quantum systems compared to the standard QRM.
• The model maintains a two-level description while effectively including the impact of higher energy states.
• Successful demonstration of the model's versatility in distinct quantum electrodynamics (QED) scenarios.

Conclusions:

• The renormalized QRM significantly enhances the precision of light-matter interaction studies in quantum electrodynamics (QED).
• This approach provides a robust framework for engineering and understanding complex quantum systems.
• The findings are particularly relevant for advancing quantum information processing technologies.