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arXiv · 1007.1747

Theory of Spectrum in Qubit-Oscillator Systems in the Ultrastrong Coupling Regime

Qing-Hu Chen·Lei Li·Tao Liu·Ke-Lin Wang
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Abstract

Recent measurement on an LC resonator magnetically coupled to a superconducting qubit[arXiv:1005.1559] shows that the system operates in the ultra-strong coupling regime and crosses the limit of validity for the rotating-wave approximation of the Jaynes-Cummings model. By using extended bosonic coherent states, we solve the Jaynes-Cummings model exactly without the rotating-wave approximation. Our numerically exact results for the spectrum of the flux qubit coupled to the LC resonator are fully consistent with the experimental observations. The smallest Bloch-Siegert shift obtained is consistent with that observed in this experiment. In addition, the Bloch-Siegert shifts in arbitrary level transitions and for arbitrary coupling constants are predicted.

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Qing-Hu Chen, Lei Li, Tao Liu, Ke-Lin Wang. 2010-07-10. Theory of Spectrum in Qubit-Oscillator Systems in the Ultrastrong Coupling Regime. https://arxiv.org/abs/1007.1747

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