Initial-state preparation for quantum phase estimation in quantum chemistry

Determine practical and efficient procedures to prepare initial quantum states with dominant overlap with the desired eigenstate (typically the ground state) of a molecular Hamiltonian for use in quantum phase estimation within fault-tolerant quantum chemistry algorithms.

Background

The paper reviews quantum phase estimation (QPE) as the standard approach to extract eigenphases (and hence energies) of molecular Hamiltonians. The success probability of QPE is proportional to the squared overlap of the initial state with the target eigenstate; thus, the initial state must have dominant overlap with the state of interest.

The authors explicitly note that creating such high-overlap initial states is currently unresolved in quantum chemistry, highlighting a key bottleneck for practical QPE-based simulations of molecular systems.