### Abstract

We calculate the transmission spectrum of a superconducting circuit realization of the Dicke model and identify spectroscopic features that can serve as signatures of the superradiant phase. In particular, we calculate the resonance frequencies of the system as functions of the bias term, which is usually absent in studies on the Dicke model but is commonly present in superconducting qubit circuits. To avoid over-complicating the proposed circuit, we assume a fixed coupling strength. This situation precludes the possibility of observing signatures of the phase transition by varying the coupling strength across the critical point. We show that the spectrum obtained by varying the bias point under fixed coupling strength can contain signatures of the normal and superradiant phases: in the normal phase one expects to observe two spectral lines, while in the superradiant phase four spectral lines are expected to exist close to the qubits' symmetry point. Provided that parameter fluctuations and decoherence rates are sufficiently small, the four spectral lines should be observable and can serve as a signature of the superradiant phase.

Original language | English |
---|---|

Article number | 063822 |

Journal | Physical Review A |

Volume | 99 |

Issue number | 6 |

DOIs | |

Publication status | Published - 18 Jun 2019 |

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### ASJC Scopus subject areas

- Atomic and Molecular Physics, and Optics

### Cite this

*Physical Review A*,

*99*(6), [063822]. https://doi.org/10.1103/PhysRevA.99.063822

**Spectrum of the Dicke model in a superconducting qubit-oscillator system.** / Ashhab, Sahel; Matsuzaki, Y.; Kakuyanagi, K.; Saito, S.; Yoshihara, F.; Fuse, T.; Semba, K.

Research output: Contribution to journal › Article

*Physical Review A*, vol. 99, no. 6, 063822. https://doi.org/10.1103/PhysRevA.99.063822

}

TY - JOUR

T1 - Spectrum of the Dicke model in a superconducting qubit-oscillator system

AU - Ashhab, Sahel

AU - Matsuzaki, Y.

AU - Kakuyanagi, K.

AU - Saito, S.

AU - Yoshihara, F.

AU - Fuse, T.

AU - Semba, K.

PY - 2019/6/18

Y1 - 2019/6/18

N2 - We calculate the transmission spectrum of a superconducting circuit realization of the Dicke model and identify spectroscopic features that can serve as signatures of the superradiant phase. In particular, we calculate the resonance frequencies of the system as functions of the bias term, which is usually absent in studies on the Dicke model but is commonly present in superconducting qubit circuits. To avoid over-complicating the proposed circuit, we assume a fixed coupling strength. This situation precludes the possibility of observing signatures of the phase transition by varying the coupling strength across the critical point. We show that the spectrum obtained by varying the bias point under fixed coupling strength can contain signatures of the normal and superradiant phases: in the normal phase one expects to observe two spectral lines, while in the superradiant phase four spectral lines are expected to exist close to the qubits' symmetry point. Provided that parameter fluctuations and decoherence rates are sufficiently small, the four spectral lines should be observable and can serve as a signature of the superradiant phase.

AB - We calculate the transmission spectrum of a superconducting circuit realization of the Dicke model and identify spectroscopic features that can serve as signatures of the superradiant phase. In particular, we calculate the resonance frequencies of the system as functions of the bias term, which is usually absent in studies on the Dicke model but is commonly present in superconducting qubit circuits. To avoid over-complicating the proposed circuit, we assume a fixed coupling strength. This situation precludes the possibility of observing signatures of the phase transition by varying the coupling strength across the critical point. We show that the spectrum obtained by varying the bias point under fixed coupling strength can contain signatures of the normal and superradiant phases: in the normal phase one expects to observe two spectral lines, while in the superradiant phase four spectral lines are expected to exist close to the qubits' symmetry point. Provided that parameter fluctuations and decoherence rates are sufficiently small, the four spectral lines should be observable and can serve as a signature of the superradiant phase.

UR - http://www.scopus.com/inward/record.url?scp=85068252025&partnerID=8YFLogxK

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U2 - 10.1103/PhysRevA.99.063822

DO - 10.1103/PhysRevA.99.063822

M3 - Article

VL - 99

JO - Physical Review A - Atomic, Molecular, and Optical Physics

JF - Physical Review A - Atomic, Molecular, and Optical Physics

SN - 1050-2947

IS - 6

M1 - 063822

ER -