Photon echo with a few photons in two-level atoms

Abstract

To store and retrieve signals at the single photon level, various photon echo\nschemes have resorted to complex preparation steps involving ancillary shelving\nstates in multi-level atoms. For the first time, we experimentally demonstrate\nphoton echo operation at such a low signal intensity without any preparation\nstep, which allows us to work with mere two-level atoms. This simplified\napproach relies on the so-coined "Revival Of Silenced Echo" (ROSE) scheme. Low\nnoise conditions are obtained by returning the atoms to the ground state before\nthe echo emission. In the present paper we manage ROSE in photon counting\nconditions, showing that very strong control fields can be compatible with\nextremely weak signals, making ROSE consistent with quantum memory\nrequirements.\n