Electromagnetically induced transparency in an optically thick, cold medium creates a unique system where pulse-propagation velocities may be orders of magnitude less than c and optical nonlinearities become exceedingly large. As a result, nonlinear processes may be efficient at low-light levels. Using an atomic system with three, independent channels, we demonstrate a quantum interference switch where a laser pulse with an energy density of ∼23 photons per λ2/(2π) causes a 1/e absorption of a second pulse.
@article{arxiv.quant-ph/0309084,
title = {Low-light-level nonlinear optics with slow light},
author = {Danielle A. Braje and Vlatko Balic and G. Y. Yin and S. E. Harris},
journal= {arXiv preprint arXiv:quant-ph/0309084},
year = {2009}
}