Bipartite and tripartite entanglement in the Two-Qubit Quantum Rabi Model

Abstract This study investigates the entanglement dynamics of the two-qubit quantum Rabi model (QRM) for both homogeneous and inhomogeneous couplings, using the adiabatic approximation. The quantized field is initially prepared in a coherent state, while a separable state and a maximally entangled Bell state are chosen as the initial two-qubit states. We characterize distinct types of entanglement generated among the subsystems via qubit-field interactions, with a focus on the bipartite entanglement between a single qubit and the field. Building on this, we examine the tripartite correlations through the I -residual tangle, a measure which conclusively verifies the presence of genuine tripartite entanglement among the two qubits and the field. This work provides a significant contribution to the generation of tunable multipartite entanglement and the detection of quantum phase transitions in light-matter systems, such as circuit QED.