Spectral collapse in the two-photon quantum Rabi model

被引：32

作者：

Armenta Rico, R. J. ^{[1
]}

Maldonado-Villamizar, F. H. ^{[2
]}

Rodriguez-Lara, B. M. ^{[3
,4
]}

机构：

[1] Univ Autonoma Sinaloa, Fac Ciencias Fisicomatemat, Calle Univ Ote,Cd Univ, Culiacan Rosales 80010, Sin, Mexico

[2] CONACYT Inst Nacl Astrofis Opt & Elect, Calle Luis Enrique Erro 1, Sta Ma Tonantzintla 72840, Pue, Mexico

[3] Tecnol Monterrey, Escuela Ingn & Ciencias, Ave Eugenio Garza Sada 2501, Monterrey 64849, NL, Mexico

[4] Inst Nacl Astrofis Opt & Electr, Calle Luis Enrique Erro 1, Sta Ma Tonantzintla 72840, Pue, Mexico

来源：

PHYSICAL REVIEW A | 2020年 / 101卷 / 06期

关键词：

32;

D O I：

10.1103/PhysRevA.101.063825

中图分类号：

O43 [光学];

学科分类号：

070207 ; 0803 ;

摘要：

Spectral collapse, the transition from a discrete to a continuous spectrum, is a characteristic in quantum Rabi models. We explore this phenomenon in the two-photon quantum Rabi model using optical phase space, and we find that, in the so-called degenerate qubit regime, the collapse is similar to the transition from a harmonic to an inverted oscillator with the free-particle potential as a critical transition point. In the degenerate qubit regime, we construct Dirac-normalizable eigenfunctions with well-defined parity for the model. In the general model, we use parity to diagonalize the system in the qubit basis and numerically find that the qubit frequency does not change the critical point where spectral collapse occurs. We numerically confirm the existence of an exceptional state at the critical coupling, and we argue its analytic provenance from both a Born-Oppenheimer and a variational approximation.

引用

页数：6