Robust switching of superposition-states via a coherent double stimulated Raman adiabatic passage

Coherent manipulation of quantum states is of crucial importance in accurate control of a quantum system. A fundamental goal is coherently transferring the population of a desired state with near-unit fidelity. For this purpose, we theoretically demonstrate a novel coherent double-stimulated Raman adiabatic passage (STIRAP) in a three-level Λ-type system for realizing the switch of unequal initial preparations on two ground states. This operation uses a single optical pulse sequence accomplishing both bright-STIRAP and dark-STIRAP processes, in which the intermediate-level detuning and the pulse delay must be given an optimal adjustment. Besides, owing to the imperfection of double-STIRAP transition, the sensitivity of the switch fidelity with respect to the spontaneous loss from the intermediate state, to the pulse amplitude and to the population difference, is also discussed. This work suggests a simple and experimentally feasible all-optical approach to switch a superposition quantum state, serving as one-step closer to the goal of coherent manipulation of quantum systems.