Author:
Thompson Kyle,Li Kehui,Angulo Daniela,Nixon Vida-Michelle,Sinclair Josiah,Sivakumar Amal Vijayalekshmi,Wiseman Howard M.,Steinberg Aephraim M.
Abstract
We show that if a photon is transmitted through an atom cloud, the time it spent as an atomic excitation along the way—as measured by weakly probing the atoms— is equal to the group delay, which can be negative.