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001018221 005__ 20240625095032.0
001018221 0247_ $$2datacite_doi$$a10.34734/FZJ-2023-04617
001018221 037__ $$aFZJ-2023-04617
001018221 088__ $$2Other$$a4443
001018221 1001_ $$0P:(DE-Juel1)200182$$aSymeonidou, Stefania$$b0$$eCorresponding author
001018221 245__ $$aThe Variational Quantum Eigensolver in Quantum Chemistry with PennyLane
001018221 260__ $$aJülich$$bForschungszentrum Jülich GmbH Zentralbibliothek,  Verlag$$c2023
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001018221 4900_ $$aBerichte des Forschungszentrums Jülich$$v4443
001018221 520__ $$aThis thesis explores quantum chemistry using the Variational Quantum Eigensolver (VQE), developed with the help of PennyLane’s quantum chemistry library. Our focus was on exploring molecular structures and energy landscapes. With an adaptive VQE implementation, we generated approximate multi-electron wave functions by optimizing a quantum circuit on a simulator. We started from a Hartree-Fock state and applied the UCCSD (Unitary Coupled Cluster Singles and Doubles) Ansatz to entangle electrons and lower the Hamiltonian’s expectation value. The journey began with H2, where the VQE accurately predicted its equilibrium distance and energy. We then extended our analysis to more complex molecules like LiH, BeH2, and H2O, successfully determining their equilibrium geometries and energies, which match existing literature. However, we discovered anomalies in the energy surfaces of BeH2 and H2O at larger internuclear distances, leading us to question the choice of initial states for these scenarios. In summary, this work demonstrated the VQE’s potential for accurate molecular simulations. While it excels in capturing ground states for various molecules, challenges remain for large internuclear distances. This sheds light on the evolving landscape of quantum technologies applied to understanding molecular systems.
001018221 536__ $$0G:(DE-HGF)POF4-5221$$a5221 - Advanced Solid-State Qubits and Qubit Systems (POF4-522)$$cPOF4-522$$fPOF IV$$x0
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001018221 9141_ $$y2023
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001018221 9201_ $$0I:(DE-Juel1)PGI-2-20110106$$kPGI-2$$lTheoretische Nanoelektronik$$x0
001018221 9201_ $$0I:(DE-Juel1)IAS-3-20090406$$kIAS-3$$lTheoretische Nanoelektronik$$x1
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