Entropy, Vol. 25, Pages 187: Superradiant Quantum Phase Transition for an Exactly Solvable Two-Qubit Spin-Boson Model

Entropy, Vol. 25, Pages 187: Superradiant Quantum Phase Transition for an Exactly Solvable Two-Qubit Spin-Boson Model

Entropy doi: 10.3390/e25020187

Authors: Roberto Grimaudo Davide Valenti Alessandro Sergi Antonino Messina

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 are characterized by abrupt changes in the two-spin subsystem concurrence, in the net spin magnetization and in the mean photon number.