Variational Quantum Eigensolver for Approximate Diagonalization of Downfolded Hamiltonians using Generalized Unitary Coupled Cluster Ansatz

• URL: http://arxiv.org/abs/2011.01985v1
• Date: Tue, 3 Nov 2020 20:03:51 GMT
• Title: Variational Quantum Eigensolver for Approximate Diagonalization of Downfolded Hamiltonians using Generalized Unitary Coupled Cluster Ansatz
• Authors: Nicholas P. Bauman and Jaroslav Chl\'adek and Libor Veis and Ji\v{r}\'i Pittner and Karol Kowalski
• Abstract summary: Generalized Unitary Coupled Cluster (GUCC) is a formalism for the diagonalization of downfolded/effective Hamiltonians in active spaces. We consider their form defined by freezing core orbitals, which enables us to deal with larger systems. We consider various solvers to identify solutions of the GUCC equations.
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• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: In this paper we discuss the utilization of Variational Quantum Solver (VQE) and recently introduced Generalized Unitary Coupled Cluster (GUCC) formalism for the diagonalization of downfolded/effective Hamiltonians in active spaces. In addition to effective Hamiltonians defined by the downfolding of a subset of virtual orbitals we also consider their form defined by freezing core orbitals, which enables us to deal with larger systems. We also consider various solvers to identify solutions of the GUCC equations. We use N$_2$, H$_2$O, and C$_2$H$_4$, and benchmark systems to illustrate the performance of the combined framework.

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