BICEP2 recently reported a detection of B-modes in the CMB polarization at degree angular scales. This B-mode pattern is widely interpreted as the likely signature from primordial gravitational waves, consistent with those predicted to arise in the first 10^-34 seconds of the history of the universe, stretched from quantum to classical scales by the exponential expansion of cosmic inflation.

BICEP2 is a CMB polarimeter that was specifically designed to search for the elusive signal from inflationary gravitational waves in the B-mode power spectra around l = 80. BICEP2 has accumulated 3 years of data from the South Pole from 2010 to 2012, integrating continuously on a low-foreground region of effective size 1% of the whole sky. I will describe the experimental strategy, tests for foreground or systematics contamination, and results in the map and power spectra. The reported B-mode spectrum is well fit by a lensed-LCDM plus tensor theoretical model with tensor/scalar ratio r = 0.20 +0.07 -0.05 with r = 0 is strongly disfavored.