Superradiant Quantum Phase Transition for an Exactly Solvable Two-Qubit Spin-Boson Model

Roberto Grimaudo; Davide Valenti; Alessandro Sergi; Antonino Messina

doi:10.3390/e25020187

Superradiant Quantum Phase Transition for an Exactly Solvable Two-Qubit Spin-Boson Model

Entropy (Basel). 2023 Jan 17;25(2):187. doi: 10.3390/e25020187.

Authors

Roberto Grimaudo¹, Davide Valenti¹, Alessandro Sergi^{2

3}, Antonino Messina⁴

Affiliations

¹ Dipartimento di Fisica e Chimica "Emilio Segrè", Group of Interdisciplinary Theoretical Physics, Università degli Studi di Palermo, Viale delle Scienze Ed. 18, 90128 Palermo, Italy.
² Dipartimento di Scienze Matematiche e Informatiche, Scienze Fisiche e Scienze della Terra, Università degli Studi di Messina, Viale F. Stagno d'Alcontres 31, 98166 Messina, Italy.
³ Institute of Systems Science, Durban University of Technology, P.O. Box 1334, Durban 4000, South Africa.
⁴ Dipartimento di Matematica ed Informatica, Università degli Studi di Palermo, Via Archirafi 34, 90123 Palermo, Italy.

Abstract

A spin-boson-like model with two interacting qubits is analysed. The model turns out to be exactly solvable since it is characterized by the exchange symmetry between the two spins. The explicit expressions of eigenstates and eigenenergies make it possible to analytically unveil the occurrence of first-order quantum phase transitions. The latter are physically relevant since they are characterized by abrupt changes in the two-spin subsystem concurrence, in the net spin magnetization and in the mean photon number.

Keywords: entanglement; exactly solvable models; open quantum systems; quantum phase transitions; superradiance; two-qubit spin-boson model.

Grants and funding

R.G. and D.V. acknowledge the financial support from PRIN Project PRJ-0232—Impact of Climate Change on the Biogeochemistry of Contaminants in the Mediterranean sea (ICCC).