  We construct a family of simple fermionic projected entangled pair states
(fPEPS) on the square lattice with bond dimension $D=3$ which are exactly
hole-doped resonating valence bond (RVB) wavefunctions with short-range singlet
bonds. Under doping the insulating RVB spin liquid evolves immediately into a
superconductor with mixed $d+is$ pairing symmetry whose pair amplitude grows as
the square-root of the doping. The relative weight between $s$-wave and
$d$-wave components can be controlled by a single variational parameter $c$. We
optimize our ansatz w.r.t. $c$ for the frustrated $t-J_1-J_2$ model (including
both nearest and next-nearest neighbor antiferromagnetic interactions $J_1$ and
$J_2$, respectively) for $J_2\simeq J_1/2$ and obtain an energy very close to
the infinite-PEPS state (using full update optimization and same bond
dimension). The orbital symmetry of the optimized RVB superconductor has
predominant d-wave character, although we argue a residual (complex s-wave)
time reversal symmetry breaking component should always be present. Connections
of the results to the physics of superconducting cuprates and pnictides are
outlined.
