The BICEP/Keck experiments are Cosmic Microwave Background (CMB) polarimeters
located at the South Pole in Antarctica. They are specifically designed to
search for the signature of primordial gravitational waves produced during the
inflationary birth of our universe. In this talk I will describe the
instruments and the analysis of multi-frequency data which allows to separate
the galactic dust foreground from a potential cosmological signal, and which
sets the world's best current limit of r<0.09 (95% CL).