Experimental evidence that a photon can spend a negative amount of time
in an atom cloud
Experimental evidence that a photon can spend a negative amount of time
in an atom cloud
When a pulse of light traverses a material, it incurs a time delay referred to as the group delay. Should the group delay experienced by photons be attributed to the time they spend as atomic excitations? However reasonable this connection may seem, it appears problematic when the frequency of the …