Adiabatic population transfer in four-level N -scheme with chirped lasers pulses

This work demonstrates efficient adiabatic and selective population transfer among arbitrary quantum states in a four-level atomic N -system using linearly chirped laser pulses. By theoretically examining the system's instantaneous eigenstates, we identify adiabatic pathways that connect each energy level to the other three, enabling controllable inter-level population transfer. A detailed analysis of key parameters including pulse intensity, chirp rate, and laser detuning reveals the optimal conditions for achieving near-unity population-transfer fidelity while keeping the population of intermediate states negligible. Moreover, because the method does not rely on strict resonance conditions, it exhibits strong robustness against small frequency fluctuations of the driving fields. Consequently, this technique could be effective in both homogeneous and inhomogeneous systems, making it a promising approach for manipulating coherent states in complex atomic environments.