Figure 1
From: Single-photon Transistors Based on the Interaction of an Emitter and Surface Plasmons
Schematic description of coherent storage of a single photon (SP) in the system consists of an emitter and a nanotip. The emitter is initially in the ground state 
and the dipole moment p of the emitter is parallel to the axis of the nanotip. Under the action of the control field Ω(t) dependent on the wave packet of the incoming photon, the capture of the incoming single photon may be realized while a state flip from 
to 
is induced.