First-order quantum phase transition in the squeezed Rabi model

Quantum phase transition and entanglement in the Rabi model with a squeezed light are investigated. We find a special unitary-transformation method that removes the nonintegrable squeezing and counterrotating-wave interactions when the qubit frequency is close to the field frequency. The analytical ground state agrees well with the numerical solution. We demonstrate that the ground state exhibits a first-order quantum phase transition at a critical point induced linearly by the squeezed light. This quantum phase transition requires neither multiple qubits nor an infinite ratio of qubit frequency to field frequency, which solves a critical problem for the theory and experiment in Rabi model. As the qubit-field coupling strength increases, the ground-state entanglement reaches its maximum value at the critical point.

Automated summary

Quantum phase transition and entanglement in the Rabi model with squeezed light were investigated. A special unitary-transformation method was found to remove nonintegrable squeezing and counter-rotating wave interactions when the qubit frequency is close to the field frequency. The analytical ground state agrees well with the numerical solution. It was demonstrated that the ground state exhibits a first-order quantum phase transition induced linearly by the squeezed light. This quantum phase transition does not require multiple qubits or an infinite ratio of qubit frequency to field frequency, addressing a critical problem in the theory and experiment of the Rabi model. As the qubit-field coupling strength increases, the ground-state entanglement reaches its maximum value at the critical point.