Variational ground state of the model of a two-state system coupled with phonons

Chen, Hong; Zhang, Yumei; Wu, Xiang

doi:10.1103/physrevb.40.11326

Cited by 34 publications

(37 citation statements)

References 12 publications

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“…A displaced coherent state for g 1, a displaced squeezed state for g 1 [17], and a superposition of two coherent states * choims@korea.ac.kr for g 1 [18,19] have been suggested as variational ground states, respectively. The accuracy of the suggested variational states was reasonable for the ground-state energy [17][18][19]. However, we find that the variational states suggested in previous work [18,19] underestimate the squeezing effect significantly in the intermediate regime (g 1); see Figs.…”

Section: Introductionmentioning

confidence: 99%

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Variational study of a two-level system coupled to a harmonic oscillator in an ultrastrong-coupling regime

Hwang

Choi²

2010

Phys. Rev. A

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The nonclassical behavior of a two-level system coupled to a harmonic oscillator is investigated in the ultrastrong coupling regime. We revisit the variational solution of the ground state and find that the existing solutions do not account accurately for nonclassical effects such as squeezing. We suggest a trial wave function and demonstrate that it has an excellent accuracy for the quantum correlation effects as well as for the energy.

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Section: Introductionmentioning

confidence: 99%

“…[17] and [19], a superposition of two displaced coherent states was suggested as a trial wave function:…”

Section: Introductionmentioning

confidence: 99%

Variational study of a two-level system coupled to a harmonic oscillator in an ultrastrong-coupling regime

Hwang

Choi²

2010

Phys. Rev. A

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“…To begin with, we consider the degree of squeezing intrinsic to the ground state of the dispersive Hamiltonian and, from there, the corresponding approximate ground state of the Rabi Hamiltonian4066676869. Noting that is a constant of motion of the dispersive Hamiltonian, the ground state of Eq.…”

Section: Resultsmentioning

confidence: 99%

Qubit-flip-induced cavity mode squeezing in the strong dispersive regime of the quantum Rabi model

Joshi

Irish

Spiller

2017

Sci Rep

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Squeezed states of light are a set of nonclassical states in which the quantum fluctuations of one quadrature component are reduced below the standard quantum limit. With less noise than the best stabilised laser sources, squeezed light is a key resource in the field of quantum technologies and has already improved sensing capabilities in areas ranging from gravitational wave detection to biomedical applications. In this work we propose a novel technique for generating squeezed states of a confined light field strongly coupled to a two-level system, or qubit, in the dispersive regime. Utilising the dispersive energy shift caused by the interaction, control of the qubit state produces a time-dependent change in the frequency of the light field. An appropriately timed sequence of sudden frequency changes reduces the quantum noise fluctuations in one quadrature of the field well below the standard quantum limit. The degree of squeezing and the time of generation are directly controlled by the number of frequency shifts applied. Even in the presence of realistic noise and imperfections, our protocol promises to be capable of generating a useful degree of squeezing with present experimental capabilities.

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“…There do exist, however, analytic treatments of the model based upon the variational principle [3][4][5][6][7][8][9]. An advantage of the variational method is that it always guarantees the groundstate energy being an upper-bound of the exact one.…”

Section: Introductionmentioning

confidence: 99%

Optimal coupled-cluster approximation for the ground-state properties of a spin-boson model

Wong

1998

Eur. Phys. J. B

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In the present work we have developed an optimal coupled-cluster approximation, which can take care of both the accuracies of the ground-state energy and the wavefunction estimates, for the ground state of a two-state system coupled to a dispersionless boson bath. This new approach is also able to give a tight upper bound to the ground-state energy of the system. Up to the fourth level of this approximation our results show excellent agreement with the numerical exact diagonalization results. In particular, our results suggest no discontinuous localization-delocalization transition of the two-state system. This is consistent with the exact result.

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Variational ground state of the model of a two-state system coupled with phonons

Cited by 34 publications

References 12 publications

Variational study of a two-level system coupled to a harmonic oscillator in an ultrastrong-coupling regime

Variational study of a two-level system coupled to a harmonic oscillator in an ultrastrong-coupling regime

Qubit-flip-induced cavity mode squeezing in the strong dispersive regime of the quantum Rabi model

Optimal coupled-cluster approximation for the ground-state properties of a spin-boson model

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