Control of photon propagation via electromagnetically induced transparency in lossless media

We study the influence of a lossless material medium on the coherent storage and quantum state transfer of a quantized probe light in an ensemble of $Λ$-type atoms. The medium is modeled as uniformly distributed two-level atoms with same energy level spacing, coupling to a probe light. This coupled system can be simplified to a collection of two-mode polaritons which couple to one transition of the $Λ$-type atoms. We show that, when the other transition of $Λ$-type atoms is controlled by a classical light, the electromagnetically induced transparency can also occur for the polaritons. In this case the coherent storage and quantum transfer for photon states are achievable through the novel dark states with respect to the polaritons. By calculating the corresponding dispersion relation, we find the ensemble of the three-level atoms with $Λ$-type transitions may serve as quantum memory for it slows or even stops the light propagation through the mechanism of electromagnetically induced transparency. the corresponding dispersion relation, we find the ensemble of the three-level atoms with $Λ$-type transitions may serve as quantum memory for it slows or even stops the light propagation through the mechanism of electromagnetically induced transparency.