Limits of single-photon storage in a single Λ -type atom

We investigate theoretically the limits of single-photon storage in a single Λ -type atom, specifically the trade-off between storage efficiency and storage speed. We show that a control field can accelerate the storage process without degrading efficiency too much. However, the storage speed is ultimately limited by the total decay rate of the excited state involved. For a single-photon pulse propagating in a regular one-dimensional waveguide, the storage efficiency has an upper limit of 50 % . Perfect single-photon storage can be achieved by using a chiral waveguide or the Sagnac interferometry. By comparing the storage efficiencies of Fock-state and coherent-state pulses, we reveal the influence of quantum statistics of light on photon storage at the single-photon level.