Selective and efficient control of population transfer in the presence of an equally populated initial doublet

Abstract

We present a way to realize selective, robust, and efficient population transfer in a ladder-type four-level system with an equally populated doublet in the initial state. By merging stimulated Raman adiabatic passage and chirped adiabatic passage techniques, we show that selective and complete population transfer from either of the initial doublet levels to the final state can be achieved with chirped pump and Stokes pulse pairs when the spectral resolution constraint of a frequency swept pulse holds (the energy separation of doublet levels should be much larger than the pulse bandwidth). We further demonstrate that the spectral resolution of selective population transfer can be enhanced significantly by using pump pulse pair and Stokes pulse due to temporal quantum interference between the sequential transitions in the time domain, which can also be well followed as a result of the frequency-domain formation of a comblike structure of the pulse pair spectrum. The proposals take into account the case of population transfer in realistic atomic and molecular systems, and may have applications in quantum coherent control of systems with equally populated initial manifolds.