Superradiant phase transition induced by the indirect Rabi interaction

TL;DR

This paper theoretically demonstrates a superradiant phase transition in an indirect Rabi model, revealing how auxiliary fields enable critical coupling and predicting a squeezed magnon cat state with potential quantum technology applications.

Contribution

It introduces a novel indirect Rabi model where the superradiant phase transition occurs via auxiliary field coupling, avoiding the $A^2$ term issues and providing analytical critical points.

Findings

Superradiant phase transition occurs at a tunable critical coupling.

Analytical expression for the quantum critical point in large detuning regime.

Prediction of a feasible squeezed magnon cat state for quantum applications.

Abstract

We theoretically study the superradiant phase transition (SPT) in an indirect Rabi model, where both a two-level system and a single mode bosonic field couple to an auxiliary bosonic field. We find that the indirect spin-field coupling induced by the virtual excitation of the auxiliary field can allow the occurrence of a SPT at a critical point, and the influence of the so-called $A^2$ term in the normal Rabi model is naturally avoided. In the large detuning regime, we present the analytical expression of quantum critical point in terms of the original system parameters. The critical atom-field coupling strength is tunable, which will loosen the conditions on realizing the SPT. Considering a hybrid magnon-cavity-qubit system, we predict the squeezed cat state of magnon generated with feasible experimental parameters, which has potential applications in quantum metrology and quantum information processing.