[4] As the photons entered the cloud, their energy excited atoms along their path, causing them to lose speed.
Inside the cloud medium, the photons dispersively coupled to strongly interacting atoms in highly excited Rydberg states.
In effect the two photons push and pull each other through the cloud as their energy is passed from one atom to the next, forcing them to interact.
[4] It may be possible to arrange the photonic molecules in such a way within the medium that they form larger two-dimensional structures (similar to drawings).
[4] The term photonic molecule has been also used since 1998 for an unrelated phenomenon involving electromagnetically interacting optical microcavities.
"[10] "Optically coupled microcavities have emerged as photonic structures with promising properties for investigation of fundamental science as well as for applications.
[13] However, other nature-inspired PM structures (such as ‘photonic benzene’) have been proposed and shown to support confined optical modes closely analogous to the ground-state molecular orbitals of their chemical counterparts.