  Lens design for focusing and imaging has been optimized through centuries of
developments; however, conventional lenses, even in their most ideal
realizations, still suffer from fundamental limitations, such as limits in
resolution and the presence of optical aberrations, which are inherent to the
laws of refraction. Although some of these limitations have been at least
theoretically relaxed with the advent of metamaterials, several challenges
still stand in the path toward ideal aberration-free imaging. Here, we show
that the concept of parity-time symmetry, combined with tailored nonlocal
response, allows overcoming some of these challenges, and we demonstrate the
design of a loss-immune, linear, transversely invariant, aberration-free
planarized metamaterial lens.
