The dark-state polaritons of a double-Λ atomic ensemble

Ding Jia-ling, Hou Bang-pin

M. Karthick Selvan

Zhuan Li, De-Zhong Cao, Kaige Wang

Johannes Otterbach, Alexey Vyacheslavovich Gorshkov, Thomas Pohl +2 more

Y. D. Chong, Marin Soljacic A

We derive the properties of polaritons in single-$\ensuremath{\Lambda}$ and double-$\ensuremath{\Lambda}$ media using a microscopic equation-of-motion technique. In each case, the polaritonic dispersion relation and composition arise from a matrix eigenvalue problem for arbitrary control field strengths. We show that the double-$\ensuremath{\Lambda}$ medium can be used to up- or down-convert single photons while preserving quantum coherence. The existence of a dark-state polariton protects this single-photon four-wave mixing effect against incoherent decay of the excited atomic states. The efficiency of this conversion is limited mainly by the sample size and the lifetime of the metastable state.

Zhuan Li

Based on the three-Λ dark-state polaritons,quantum information can be exchanged not only between the three-signal fields and the collective atoms,but also among the three signal fields.Some three-mode quantum states can be stored in the three-Λ atomic ensemble,thus the quantum information of the three-signal field can be written and read in the medium.Furthermore,with this scheme some tripartite entangled states can be generated,stored,retrieved,transformed and so on,thus the ability of the manipulation of entangled states is improved.