  An infinite projected entangled-pair state (iPEPS) is a variational tensor
network ansatz for 2D wave functions in the thermodynamic limit where the
accuracy can be systematically controlled by the bond dimension $D$. We show
that for the doped Hubbard model in the strongly correlated regime ($U/t=8$,
$n=0.875$) iPEPS yields lower variational energies than state-of-the-art
variational methods in the large 2D limit, which demonstrates the
competitiveness of the method. In order to obtain an accurate estimate of the
energy in the exact infinite $D$ limit we introduce and test an extrapolation
technique based on a truncation error computed in the iPEPS imaginary time
evolution algorithm. The extrapolated energies are compared with accurate
quantum Monte Carlo results at half filling and with various other methods in
the doped, strongly correlated regime.
