期刊
PHYSICAL REVIEW A
卷 105, 期 2, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevA.105.023704
关键词
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资金
- Romanian Core Program [PN19-03, 21 N/08.02.2019]
In this paper, we revisit the theoretical description of the ultrastrong light-matter interaction and propose an improved effective Hamiltonian that can accurately calculate operator averages and excitations.
We revisit the theoretical description of the ultrastrong light-matter interaction in terms of exactly solvable effective Hamiltonians. A perturbative approach based on polaronic and spin-dependent squeezing transforma-tions provides an effective Hamiltonian for the quantum Rabi model up to the second order in the expansion parameter. The model consistently includes both rotating and counter-rotating terms, going therefore beyond the rotating-wave approximation. Analytical and numerical results show that the proposed Hamiltonian performs better than the Bloch-Siegert model when calculating operator averages (e.g., the mean photon number and number of excitations). This improvement is due to a refined calculation of the dressed states within the present model. Regarding the frequency shift induced by the qubit-photon interaction, we find a different sign from the Bloch-Siegert value. This influences the structure of the eigenstates in a nontrivial way and ensures the correct calculation of the number of excitations associated with a given dressed state. As a consistency check, we show that the exactly solvable independent boson model is reproduced as a special limit case of the perturbative Hamiltonian.
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