Abstract

One of the main goals of modern observational cosmology is to constrain or detect a stochastic background of primordial gravitational waves. Realising this goal will rely on highly accurate measurements of the B-mode signature in the cosmic microwave background (CMB). In this talk I will give an overview of the associated experimental challenges and in particular demonstrate how B-mode inference is biased by poorly understood optical properties. I will discuss methods to model these optical systematics efficiently. I will then concentrate on a particular dedicated B-mode experiment: the balloon-borne SPIDER polarimeter. I will present preliminary results from the first flight and prospects for the second flight. Finally I will explain how, in principle, upcoming B-mode data will allow us to probe relatively unexplored assumptions about the early universe. I will show how to adapt existing bispectrum estimators to extract this information from B-mode data.