B-mode polarisation from the ground: recent constraints from the POLARBEAR experiment and prospect for the future
CMB B-mode polarisation observations of the primordial gravitational wave signal provide a powerful probe of the inflationary universe, and the small-scale lensing B-modes also give an accurate integrated measure of large-scale structure out to high redshift (peaking around z~2). For few years, CMB ground-based experiments are putting together large telescopes with powerful detectors to target the faint B-mode signal and extract the cosmological informations from the jungle of contaminants. The first results confirming the existence of lensing B-modes have been published, but advancing beyond this will require significant improvements both in technology and data analysis. With future high resolution CMB observatories such as Simons Observatory or CMB-S4 upcoming, B-mode study in general and lensing reconstruction in particular, will enter in an era of high precision which will also necessitate greater theoretical modelling to improve the range of scales that can be analysed.