Dipole-Dipole Broadening in $^{85}$Rb Rydberg Samples

A key interesting property of high-n Rydberg atoms is their large transition dipole moments. These dipole moments allow for observation and manipulation of electric dipole-dipole interactions between Rydberg atoms -- a key for quantum computing schemes. We measured the strength of the dipole-dipole interaction vs. Rydberg atom density in a magneto-optical trap -- specifically we measured the linewidths of microwave ns-np transitions and observed broadening of up 100 MHz.