AGP-based unitary coupled cluster theory for quantum computers
Armin Khamoshi, Guo P. Chen, Francesco A. Evangelista, Gustavo E. Scuseria · Quantum Science and Technology · 2022
Abstract Electronic structure methods typically benefit from symmetry breaking and restoration, specially in the strong correlation regime. The same goes for ansätze on a quantum computer. We develop a unitary coupled cluster method based on the antisymmetrized geminal power (AGP)—a state formally equivalent to the number-projected Bardeen–Cooper–Schrieffer wavefunction. We demonstrate our method for the single-band Fermi–Hubbard Hamiltonian in one and two dimensions. We also explore post-selection as a state preparation step to obtain correlated AGP and prove that it scales no worse than O ( M ) in the number of measurements, thereby making it a less expensive alternative to gauge integration to restore particle number symmetry.