Electric and magnetic dipolar interactions between atoms are ubiquitous. In many cases they are responsible for the formation of molecules, the emergence of magnetism, as well as many other physical phenomena. Usually these interactions decay as the cube of the distance between atoms and are therefore dominant only on atomic scale separations between atoms. Here I’ll describe the measurement of dipolar interactions between atomic ions that are separated by several micrometers in trapped-ion crystals. I’ll describe the measurement of the magnetic dipolar interaction between the two valence electrons of two ions as well as the collective Lamb-shift which arises from resonant electric dipole interaction between ions.
 Measurement of the magnetic interaction between two bound electrons of two separate ions, Shlomi Kotler, Nitzan Akerman, Nir Navon, Yinnon Glickman, Roee Ozeri, Nature 510, 376 (2014)
 Cooperative Lamb shift in a mesoscopic atomic array, Ziv Meir, Osip Schwartz, Ephraim Shahmoon, Dan Oron, Roee Ozeri, Phys. Rev. Lett. 113, 193002 (2014)