Exact and approximate symmetry projectors for the electronic structure problem on a quantum computer

Solving the electronic structure problem on a universal-gate quantum computer within the variational quantum eigensolver (VQE) methodology requires constraining the search procedure to a subspace defined by relevant physical symmetries. Ignoring symmetries results in convergence to the lowest eigens...

Full description

Saved in:
Bibliographic Details
Published in:The Journal of chemical physics 2019-10, Vol.151 (16), p.164111-164111
Main Authors: Yen, Tzu-Ching, Lang, Robert A., Izmaylov, Artur F.
Format: Article
Language:English
Subjects:
Approximation
Eigenvectors
Electronic structure
Electrons
Forecasting
Optimization
Projectors
Quantum computers
Quantum computing
Symmetry
Wave functions
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Solving the electronic structure problem on a universal-gate quantum computer within the variational quantum eigensolver (VQE) methodology requires constraining the search procedure to a subspace defined by relevant physical symmetries. Ignoring symmetries results in convergence to the lowest eigenstate of the Fock space for the second quantized electronic Hamiltonian. Moreover, this eigenstate can be symmetry broken due to limitations of the wavefunction ansatz. To address this VQE problem, we introduce and assess methods of exact and approximate projectors to irreducible eigensubspaces of available physical symmetries. Feasibility of symmetry projectors in the VQE framework is discussed, and their efficiency is compared with symmetry constraint optimization procedures. Generally, projectors introduce a higher number of terms for VQE measurement compared to the constraint approach. On the other hand, the projection formalism improves accuracy of the variational wavefunction ansatz without introducing additional unitary transformations, which is beneficial for reducing depths of quantum circuits.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.5110682