6.7. Ab-initio methods using quantum computing
Quantum computers hold promise to enable efficient simulations of the
properties of molecules and materials; however, at present, their
abilities are limited due to a limited number of qubits that can be
realized. In the near-term, the throughput of quantum computers is
limited by the small number of qubits available, which prohibits large
systems. It is more practical to develop hybrid quantum-classical
methods where the quantum computation is restricted to a small portion
of the system; for example, molecules where an active region requires a
higher level of theoretical accuracy than its environment. Galli et al.
outline 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 [169]. The
authors demonstrate the efficacy of the method by investigating defect
quantum bits in semiconductors that are of great interest for quantum
information technologies. The calculations are performed on quantum
computers and show that they yield results in agreement with those
obtained with exact diagonalization on classical architectures, paving
the way to simulations of realistic materials on near-term quantum
computers.