Quantum state engineering in a three-level system with periodical Gaussian pulses

In this paper, we propose a scheme to achieve selective population transfer in a Λ-type three-level atomic system with a train of periodical Gaussian pulses. Based on temporal constructive quantum interference between the sequential transitions and subsequent coherent accumulations, the selective population transfer can be achieved with the pulse train, without satisfying the requirement of two-photon resonance condition. It can be understood as a result of the formation of a comb-like structure of the pulse train spectrum in time domain. Numerical simulations demonstrate that the scheme is robust against the wave-form deformation of single pulse while sensitive to the pulse train repetition period. Due to the Gaussian waveform of the laser field been readily implemented in experiments, the scheme holds great practicality for quantum state engineering in quantum information processing.