Digital quantum simulation of strong correlation effects with iterative quantum phase estimation over the variational quantum eigensolver algorithm: $\mathrm{H_4}$ on a circle as a case study

Variational quantum eigensolver simulations with the multireference unitary coupled cluster ansatz: a case study of the C2v quasi-reaction pathway of beryllium insertion into a H2 molecule

“…One of the anticipated applications of the VQE is the preparation of approximate wave functions for the input of the QPE-based full-CI. 96 The QPE utilizes a projective measurement to obtain the full-CI energy, and therefore using the wave function having a large overlap with the full-CI is very important. 3 In this context, the conventional SR-UCCSD is less appropriate than the twoconfigurational wave functions constructed using the diradical characters for the initial wave functions of the QPE, 95 unless this slow convergence problem is resolved.…”

Adiabatic state preparation of correlated wave functions with nonlinear scheduling functions and broken-symmetry wave functions

“…Molecules having electronic structures too complicated to deal with facile approaches like density functional theory (DFT) are naturally one of the main targets of sophisticated quantum chemical calculations, and the development of theoretical methods to generate correlated wave functions considering both static and dynamical electron correlation effects on quantum computers is an important task. Note that one of the anticipated usage of VQE is the preparation of approximate wave functions used as the input for QPE 17 , but recent numerical simulations of VQE of the C 2v quasi-reaction pathway of Be + H 2 → BeH 2 reaction revealed that the variational parameter optimization converges very slowly for strongly correlated systems 18 .…”