Robust Preparation of Many-body Ground States in Jaynes-Cummings Lattices*

Strongly-correlated polaritons in Jaynes-Cummings (JC) lattices can exhibit novel quantum phase transitions at integer fillings. However, it is often challenging to prepare such states with high fidelity, especially near the quantum critical points with a vanishing energy gap. Here we study the robust preparation of the many-body ground states of polaritons in a finite-sized JC lattice by combining the techniques of quantum state engineering and adiabatic evolution. In the deep Mott-insulating or deep superfluid regimes, the many-body ground states can be generated with high fidelity by applying quantum-engineered pulse sequences to the JC lattice. Using these states as the initial state and tuning the system parameters adiabatically, the many-body ground states in the intermediate regime can be reached. Our numerical result shows that the fidelity of the generated states can be significantly improved by employing a nonlinear ramping scheme during the adiabatic evolution. We derive the optimal nonlinear index analytically, which agrees well with the numerical result. This study gives insights into the preparation of many-body states in artificial quantum systems, such as quantum simulators.