  Polar codes, introduced recently by Ar\i kan, are the first family of codes
known to achieve capacity of symmetric channels using a low complexity
successive cancellation decoder. Although these codes, combined with successive
cancellation, are optimal in this respect, their finite-length performance is
not record breaking. We discuss several techniques through which their
finite-length performance can be improved. We also study the performance of
these codes in the context of source coding, both lossless and lossy, in the
single-user context as well as for distributed applications.
