Abstract
We have studied the role of degenerate Zeeman states in the storage and retrieval of light pulses in the three-level Λ -type system of electromagnetically induced transparency. A probe pulse with the σ+ polarization is stored in the medium and subsequently released with the σ- polarization. However, the manipulation of the retrieved polarization causes an energy loss. Our study shows that the incompatibility between the stored ground-state coherence and the ratio of the probe and coupling Clebsch-Gordan coefficients is responsible for the energy loss. Such energy loss can be avoided as long as all population accumulates in a single Zeeman state. We provide the useful knowledge for the light-storage technique and demonstrate that the degenerate Zeeman states should be considered in the relevant applications. © 2007 The American Physical Society.