Tuesday, June 11, 2013

1306.2122 (Li-Tuo Shen et al.)

Ground state of the asymmetric Rabi model in the ultrastrong coupling

Li-Tuo Shen, Zhen-Biao Yang, Mei Lu, Rong-Xin Chen, Huai-Zhi Wu
We study the ground states of the asymmetric single- and two-qubit Rabi models, in which the coupling strengthes for the counter-rotating wave and rotating wave interactions are different. We take the transformation method to analytically solve the ground states for both Rabi models and numerically verify it to be valid under a wide range of parameters. We find that the ground state energy in the single- or two-qubit Rabi model has an approximately quadratic dependence on the coupling strengthes stemming from different contributions of the counter-rotating wave and rotating wave interactions. For the single-qubit Rabi model, we show the accuracy of results can be further improved by the second-order perturbation correction. Interestingly, for the two-qubit Rabi model, we find that after the ground state entanglement reaches its maximum it decreases to zero with the increase of the coupling strength in the counter-rotating wave or rotating wave interaction, and never increases again when the qubit-oscillator coupling strength is further increased. Furthermore, the maximum of the ground state entanglement in the asymmetric two-qubit Rabi model is far larger than that in the symmetric two-qubit Rabi model.
View original: http://arxiv.org/abs/1306.2122

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