  Simulating chemical systems on quantum computers has been limited to a few
electrons in a minimal basis. We demonstrate experimentally that the virtual
quantum subspace expansion [Phys. Rev. X 10, 011004 (2020)] can achieve full
basis accuracy for hydrogen and lithium dimers, comparable to simulations
requiring twenty or more qubits. We developed an approach to minimize the
impact of experimental noise on the stability of the generalized eigenvalue
problem, a crucial component of the quantum algorithm. In addition, we were
able to obtain an accurate potential energy curve for the nitrogen dimer in a
quantum simulation on a classical computer.
