Cavity quantum electrodynamic (QED) is studied for two strongly-coupled charge qubits interacting with a single-mode quantized field, which is provided by a on-chip transmission line resonator. We analyze the dressed state structure of this superconducting circuit QED system and the selection rules of electromagnetic-induced transitions between any two of these dressed states. Its macroscopic quantum criticality, in the form of ground state level crossing, is also analyzed, resulting from competition between the Ising-type inter-qubit coupling and the controllable on-site potentials.
@article{arxiv.quant-ph/0601026,
title = {Macroscopic Quantum Criticality in a Circuit QED},
author = {Y. D. Wang and H. T. Quan and Yu-xi Liu and C. P. Sun and Franco Nori},
journal= {arXiv preprint arXiv:quant-ph/0601026},
year = {2007}
}