Qubit-efficient quantum chemistry with the ADAPT variational quantum eigensolver and double unitary downfolding

• URL: http://arxiv.org/abs/2504.18683v1
• Date: Fri, 25 Apr 2025 20:24:07 GMT
• Title: Qubit-efficient quantum chemistry with the ADAPT variational quantum eigensolver and double unitary downfolding
• Authors: Harjeet Singh, Luke W. Bertels, Daniel Claudino, Sophia E. Economou, Edwin Barnes, Nicholas P. Bauman, Karol Kowalski, Nicholas J. Mayhall,
• Abstract summary: We benchmark the ability of DUCC effective Hamiltonians to recover dynamical correlation energy outside of an active space.<n>We observe similar convergence of the ground state as compared to bare active space Hamiltonians, demonstrating that DUCC Hamiltonians provide increased accuracy without increasing the load on the quantum processor.
• Score: 0.7361163215281896
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: In this work, we combine the recently developed double unitary coupled cluster (DUCC) theory with the adaptive, problem-tailored variational quantum eigensolver (ADAPT-VQE) to explore accuracy of unitary downfolded Hamiltonians for quantum simulation of chemistry. We benchmark the ability of DUCC effective Hamiltonians to recover dynamical correlation energy outside of an active space. We consider the effects of strong correlation, commutator truncation, higher-body terms, and approximate external amplitudes on the accuracy of these effective Hamiltonians. When combining these DUCC Hamiltonians with ADAPT-VQE, we observe similar convergence of the ground state as compared to bare active space Hamiltonians, demonstrating that DUCC Hamiltonians provide increased accuracy without increasing the load on the quantum processor.

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