  An ingeniously designed autoencoder (PrimeNet) using simulated observations
of future generation ECHO satellite mission recovers CMB B mode map, angular
spectrum for multipoles $\ell \lesssim 9$ and tensor to scalar ratio $r$ {\it
limited only by cosmic variance down to $r= 0.0001$ and below}. We use diverse,
realistically complex and detailed foreground models. PrimeNet predicts
accurate results even when data with $r=0$ are tested which were not used in
training, implying robust and efficient predictive power. The work eliminates a
major bottleneck of weak CMB B mode reconstruction and takes a leap forward for
understanding fundamental physics of the primordial Universe.
