Quantum simulations of materials on near-term quantum computers

Quantum computers hold promise to enable efficient simulations of the properties of molecules and materials; however, at present they only permit ab initio calculations of a few atoms, due to a limited number of qubits. In order to harness the power of near-term quantum computers for simulations of larger systems, it is desirable to develop hybrid quantum-classical methods where the quantum computation is restricted to a small portion of the system. This is of particular relevance for molecules and solids where an active region requires a higher level of theoretical accuracy than its environment. We present a quantum embedding theory for the calculation of strongly-correlated electronic states of active regions, with the rest of the system described within density functional theory. We demonstrate the effectiveness of the approach by investigating spin-defects in semiconductors that are relevant for quantum information science. We discuss calculations on quantum computers and show that they yield results in agreement with those obtained with exact diagonalization on classical architectures¹, paving the way to simulations of realistic materials on near-term quantum computers.
[1] Ma et al., npj Comput. Mater. 6, 85 (2020).