Novel Quantum Chemistry Algorithms Based on the Variational  Quantum Eigensolver

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dc.contributor.authorGrimsley, Harper Rexen
dc.contributor.committeechairMayhall, Nicholasen
dc.contributor.committeememberValeyev, Eduard Faritovichen
dc.contributor.committeememberEconomou, Sophia E.en
dc.contributor.committeememberCrawford, Danielen
dc.contributor.departmentChemistryen
dc.date.accessioned2023-02-04T09:00:26Zen
dc.date.available2023-02-04T09:00:26Zen
dc.date.issued2023-02-03en
dc.description.abstractThe variational quantum eigensolver (VQE) approach is currently one of the most promising strategies for simulating chemical systems on quantum hardware. In this work, I will describe a new quantum algorithm and a new set of classical algorithms based on VQE. The quantum algorithm, ADAPT-VQE, shows promise in mitigating many of the known limitations of VQEs: Ansatz ambiguity, local minima, and barren plateaus are all addressed to varying degrees by ADAPT-VQE. The classical algorithm family, O2DX-UCCSD, draws inspiration from VQEs, but is classically solvable in polynomial time. This group of algorithms yields equations similar to those of the linearized coupled cluster theory (LCCSD) but is more systematically improvable and, for X = 3 or X = ∞, can break single bonds, which LCCSD cannot do. The overall aim of this work is to showcase the richness of the VQE algorithm and the breadth of its derivative applications.en
dc.description.abstractgeneralA core goal of quantum chemistry is to compute accurate ground-state energies for molecules. Quantum computers promise to simulate quantum systems in ways that classical computers cannot. It is believed that quantum computers may be able to characterize molecules that are too large for classical computers to treat accurately. One approach to this is the variational quantum eigensolver, or VQE. The idea of a VQE is to use a quantum computer to measure the molecular energy associated with a quantum state which is parametrized by some classical set of parameters. A classical computer will use a classical optimization scheme to update those parameters before the quantum computer measures the energy again. This loop is expected to minimize the quantum resources needed for a quantum computer to be useful, since much of the work is outsourced to classical computers. In this work, I describe two novel algorithms based on the VQE which solve some of its problems.en
dc.description.degreeDoctor of Philosophyen
dc.format.mediumETDen
dc.identifier.othervt_gsexam:36017en
dc.identifier.urihttp://hdl.handle.net/10919/113663en
dc.language.isoenen
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectQuantum Chemistryen
dc.subjectQuantum Computingen
dc.subjectVariational Quantum Eigensolveren
dc.subjectUnitary Coupled Clusteren
dc.titleNovel Quantum Chemistry Algorithms Based on the Variational  Quantum Eigensolveren
dc.typeDissertationen
thesis.degree.disciplineChemistryen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.nameDoctor of Philosophyen

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