Searching for Primordial Gravitational Waves with CMB-S4

Observations of the cosmic microwave background have been key to our understanding of the early universe. The cosmic microwave background also contains invaluable information about particle physics that can be revealed through precision observations of the polarization anisotropies. In this talk I will review the implications of a detection of primordial gravitational waves from the early Universe and discuss the expected sensitivity for the next generation ground-based CMB experiment CMB-S4.