Quantum simulations of molecular systems with intrinsic atomic orbitals
Quantum simulations of molecular systems on quantum computers often employ
minimal basis sets of Gaussian orbitals. In comparison with more realistic
basis sets, quantum simulations employing minimal basis sets require fewer
qubits and quantum gates, but yield results of lower accuracy. A natural
strategy to achieve more accurate results is to increase the basis set size,
which in turn requires increasing the number of qubits and quantum gates. Here
we explore the use of intrinsic atomic orbitals (IAOs) in quantum simulations
of molecules, to improve the accuracy of energies and properties at the same
computational cost required by a minimal basis. We investigate ground-state
energies and one- and two-body density operators in the framework of the
variational quantum eigensolver, employing and comparing different Ans\"{a}tze.
We also demonstrate the use of this approach in the calculation of ground- and
excited-states energies of small molecules by a combination of quantum
algorithms, using IBM Quantum computers.
Stefano Barison Davide Emilio Galli Mario Motta