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arXiv · 1306.2122

Ground state of the asymmetric Rabi model in the ultrastrong coupling regime

Li-Tuo Shen·Zhen-Biao Yang·Mei Lu·Rong-Xin Chen·Huai-Zhi Wu
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Abstract

We study the ground states of the single- and two-qubit asymmetric Rabi models, in which the qubit-oscillator coupling strengths for the counterrotating-wave and corotating-wave interactions are unequal. We take the transformation method to obtain the approximately analytical ground states for both models and numerically verify its validity for a wide range of parameters under the near-resonance condition. We find that the ground-state energy in either the single- or two-qubit asymmetric Rabi model has an approximately quadratic dependence on the coupling strengths stemming from different contributions of the counterrotating-wave and corotating-wave interactions. For both models, we show that the ground-state energy is mainly contributed by the counterrotating-wave interaction. Interestingly, for the two-qubit asymmetric Rabi model, we find that, with the increase of the coupling strength in the counterrotating-wave or corotating-wave interaction, the two-qubit entanglement first reaches its maximum then drops to zero. Furthermore, the maximum of the two-qubit entanglement in the two-qubit asymmetric Rabi model can be much larger than that in the two-qubit symmetric Rabi model.

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Li-Tuo Shen, Zhen-Biao Yang, Mei Lu, Rong-Xin Chen, Huai-Zhi Wu. 2014-09-20. Ground state of the asymmetric Rabi model in the ultrastrong coupling regime. https://doi.org/10.1007/s00340-014-5821-2

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