Simple variational ground state and pure-cat-state generation in the quantum Rabi model
Catherine Leroux, Luke C. G. Govia, Aashish A. Clerk · Physical Review A · 2017
We introduce a simple, physically motivated variational ground state for the quantum Rabi model and demonstrate that it provides a high-fidelity approximation of the true ground state in all parameter regimes (including intermediate- and strong-coupling regimes). Our variational state is constructed using Gaussian cavity states and nonorthogonal qubit pointer states and contains only three variational parameters. We use our state to develop a heuristic understanding of how the ground state evolves with increasing coupling and find a parameter regime where the ground state corresponds to the cavity being in a nearly pure Schr\"odinger cat state.